New engine/low HP

I'm no expert, but from all the other postings that I've seen over time the Performer intake is probably choking your engine. I have a Blue Thunder intake and all fit under the screen (barely) when I was running it.

Art, one thing you might try that is relatively inexpensive is maybe a differant air cleaner?? I know the air has to make some sharp turns before it can head down the carb and if there isn't a lot of room between your air horns and the top of the air cleaner, it acts like a restriction. I heard thos dog bone ones are actually pretty good.

Hi Art,

2511 runs a .030 over Cleveland, Performer, Holley 670, a dropped Moroso cleaner that makes the air work to get down the carb throat, and the big Ansa GTS headers/mufflers. My cam is very mild compared to yours, but my chassis dyno had HP climbing to 292 at about 6150 until it dropped off like a rock.

What size is that Big Bore choking your exhaust down to? Primaries?

Sounds like air flow issues - intake/exhaust/both?

Larry

Art the intake's gotta go... some of the other biys can give you a recommendation but thats a street intake. I have a torker you can try and it fits under the screen with a Moroso air cleaner brand new black. Both are for sale.

The power valve which did you select .. if I remember correctly you need a vacumn guage and what ever vacumn you have at idle you need 1 point higher or lower. its been a while maybe some one can clarify that. Jetting .. you need a selection of jets DYNO day.

Keep trying the HP will come up.

Ron

Art,
What did they end up chargeing for those pulls,I was thinking of taking mine over to dyno. or better yet lets get a dyno day going.
My 1/2 cent: ditch the intake and open the headers.

Art,

the dyno is the best place to diagnose a problem. I have more questions than answers at this point.

First, my random observations. Your motor is making about 407 bhp at the flywheel, which is about all you're going to make using the cast iron 4V heads without porting & a good valve job (multi angle). Although the cam is rated for power out to 6000 rpm by Comp Cams, thats with a 351 cubic inch motor, the extra displacement of your stroker moves the power band lower in rpm, I would have guessed power to 5750 rpm, but 5650 is close enough. David Berman had his motor dyno tested with an Edelbrock Performer adapted to work with his Blue Thunder heads, that motor made a tad more than 500 bhp, at around 6000 rpm, feeding a 408 cubic inches. I never liked the Performer myself, but David's dyno results has given me a new found appreciation of that intake, you can make more power at the upper rpm with other intakes for sure, but I do not believe the intake is what is "choking" your motor. It may very well be the characteristics of that cam to drop off like a brick above the powerband, rather than the torque curve tapering downward at a slower rate, which is why sports car guys normally want a wide flat torque curve, rather than an upward tilted one. The upward tilted ones drop off faster beyond peak torque. When all is said and done, you may very well need a custom ground cam to get the characterisitcs you want.

Having written all that, I myself would not be satisfied with the performance of your motor either. I would expect it to perform better too.

OK, here's my questions:

Do you have assurance that the person who built your short block did a good job with the rings as far as getting them to seal well in the cylinders?

Did the dyno operators run any air/fuel ratio numbers while your motor was on their dyno? If so, what were the numbers like between 4000 & 6000 rpm?

What components is your ignition composed of, and how old are they?

What is your ignition timing specs?

What parts are your fuel delivery system composed of & how old are they?

What make & size is your carburetor?

What are you using for an air filter and was it installed during dyno testing?

What size are the exhaust pipes of the mind train system, and what type mufflers does it use?

Have your heads been ported and had a multi angle valve job?

How do the specs of the Isky 8005A springs compare to the springs recommended by Comp Cams?

your friend on the DTBB

Thank You Dennis,
Art

quote:

Originally posted by 4NFORD:
I'm no expert, but from all the other postings that I've seen over time the Performer intake is probably choking your engine. I have a Blue Thunder intake and all fit under the screen (barely) when I was running it.

I am using a 3-1/2" tall round K+N filter. When I had the carb worked on this week, I had them mill off the choke horn in anticipation of squeezing a taller manifold under the screen. Milling the choke horn gave me no seat of the pants improvement. So, I don't think the air filter is holding me back?
Thanks,
Art

quote:

Originally posted by DeTom:
Art, one thing you might try that is relatively inexpensive is maybe a differant air cleaner?? I know the air has to make some sharp turns before it can head down the carb and if there isn't a lot of room between your air horns and the top of the air cleaner, it acts like a restriction. I heard thos dog bone ones are actually pretty good.

Larry,
The primaries (header tubes) are 2" OD which I guess makes them 1-7/8's. The exhaust pipe from the headers to the four glass packs is about 2-1/4" OD so I guess you would call it 2-1/8".
Thanks,
Art

quote:

Originally posted by LF - TP 2511:
Hi Art,

2511 runs a .030 over Cleveland, Performer, Holley 670, a dropped Moroso cleaner that makes the air work to get down the carb throat, and the big Ansa GTS headers/mufflers. My cam is very mild compared to yours, but my chassis dyno had HP climbing to 292 at about 6150 until it dropped off like a rock.

What size is that Big Bore choking your exhaust down to? Primaries?

Sounds like air flow issues - intake/exhaust/both?

Larry

Ron,
I don't know which power valve they installed. I also did not realize a Torker manifold would fit under the screen. Is that the later screen with the raised sheet metal section?
Thanks,
Art

quote:

Originally posted by accobra:
Art the intake's gotta go... some of the other biys can give you a recommendation but thats a street intake. I have a torker you can try and it fits under the screen with a Moroso air cleaner brand new black. Both are for sale.

The power valve which did you select .. if I remember correctly you need a vacumn guage and what ever vacumn you have at idle you need 1 point higher or lower. its been a while maybe some one can clarify that. Jetting .. you need a selection of jets DYNO day.

Keep trying the HP will come up.

Ron

Dennis,
They charged me $150 the first time which was just a diagnosis with no dyno pull. They charged me $130 the second visit which included three or four pulls? Their regular price is $180 with no changing of jets, $300 or $310 if they change jets. A dyno day would be cool!
Thanks,
Art

quote:

Originally posted by daleyracing:
Art,
What did they end up chargeing for those pulls,I was thinking of taking mine over to dyno. or better yet lets get a dyno day going.
My 1/2 cent: ditch the intake and open the headers.

Dennis,
Do you have the same cam as I do, the Comp Cams #32-541-8 hydraulic roller? If so, what kind of rpm's can you turn? It sounds like your engine screams!
Art

quote:

Originally posted by daleyracing:
Art,
What did they end up chargeing for those pulls,I was thinking of taking mine over to dyno. or better yet lets get a dyno day going.
My 1/2 cent: ditch the intake and open the headers.

George,
Russ Fulp built my engine, he has also built engines for Dennis Antennucci, Dennis Daley and Matt Meritt. Russ has a very good reputation. As for rings seating in the cylinders, I don't know? A problem started early on with excessive oil consumption, like a quart every 200 miles. That turned out to be bad intake gaskets (Mr. Gasket) that I replaced with Fel-Pro's. I'm not sure that has completely solved the oil consumtion problem, I suspect there is a little blow by going on. Russ says he sets his engines up loose, but I'm not sure my rings seated properly? The dyno guys gave me no air/fuel info. My ignition includes a new msd 6-al box with a 6500 rev limiting chip. The distributor is a Ford, Duraspark? The coil is an Accel Super Stock #8140C, a typical looking cylindrical unit. The coil is seven years old with about 18,000 miles on it. The distributor was in the car when I bought it in 1997, I've put about 30,000 miles on the car and distributor. The guys at the dyno shop set the timing to 34 degrees total, I noticed they plugged my vacuum advance, it is still plugged. I have all new fuel lines and filter. I have a new mechanical fuel pump that is supposed to be good for 120 gph. It is an Allstar brand #40263. The dyno guys watched my fuel pressure gauge during the pull and they said pressure never dropped below 6 psi. I have a Holley 750 double pumper with mechanical secondaries. I believe it is a 4150/4779. It was set up by Jet Performance for my new engine. I am using a 3.5" tall round K+N part #E-1540 air filter. The air filter was in place during the dyno test. The headers appear to have 1-7/8 inch primary tubes with 2-1/4 O.D. exhaust pipes running into four glass packs. The heads were not ported, but Russ did a multi angle valve job on them. I haven't found the specs for the Isky or the Comp Cams springs. I guess I should ask Russ why he chose to go with the Iskys. I hope you are wrong about the cam, (that intake sure would be a lot easier to change), but you seem to be very knowledgeable about this stuff.
Thank you very much for your help,
Art

quote:

Originally posted by george pence:
Art,

the dyno is the best place to diagnose a problem. I have more questions than answers at this point.

First, my random observations. Your motor is making about 407 bhp at the flywheel, which is about all you're going to make using the cast iron 4V heads without porting & a good valve job (multi angle). Although the cam is rated for power out to 6000 rpm by Comp Cams, thats with a 351 cubic inch motor, the extra displacement of your stroker moves the power band lower in rpm, I would have guessed power to 5750 rpm, but 5650 is close enough. David Berman had his motor dyno tested with an Edelbrock Performer adapted to work with his Blue Thunder heads, that motor made a tad more than 500 bhp, at around 6000 rpm, feeding a 408 cubic inches. I never liked the Performer myself, but David's dyno results has given me a new found appreciation of that intake, you can make more power at the upper rpm with other intakes for sure, but I do not believe the intake is what is "choking" your motor. It may very well be the characteristics of that cam to drop off like a brick above the powerband, rather than the torque curve tapering downward at a slower rate, which is why sports car guys normally want a wide flat torque curve, rather than an upward tilted one. The upward tilted ones drop off faster beyond peak torque. When all is said and done, you may very well need a custom ground cam to get the characterisitcs you want.

Having written all that, I myself would not be satisfied with the performance of your motor either. I would expect it to perform better too.

OK, here's my questions:

Do you have assurance that the person who built your short block did a good job with the rings as far as getting them to seal well in the cylinders?

Did the dyno operators run any air/fuel ratio numbers while your motor was on their dyno? If so, what were the numbers like between 4000 & 6000 rpm?

What components is your ignition composed of, and how old are they?

What is your ignition timing specs?

What parts are your fuel delivery system composed of & how old are they?

What make & size is your carburetor?

What are you using for an air filter and was it installed during dyno testing?

What size are the exhaust pipes of the mind train system, and what type mufflers does it use?

Have your heads been ported and had a multi angle valve job?

How do the specs of the Isky 8005A springs compare to the springs recommended by Comp Cams?

your friend on the DTBB

Art,

Thanks for providing the info, sorry for the third degree.

have you spoken to Russ about this? I know who Russ is because other Pantera owners like Dennis A speak very highly of him. I would expect him to have built you a top notch motor, and am surprised to read you're having trouble with it knowing he's the builder. There's a mechanics code of honor by the way, one mechanic doesn't criticize or second guess the work of another, at least not publicly, ahem.... Mechanics are all a very highly opinionated bunch, become irritated easily. If we went around second guessing each other, we'd end up throwing burning carburetors through each others windows in the middle of the night. You've never heard of a "Holley-tof cocktail"?

Shame on your dyno operators for not taking A/F ratio readings! That would have provided you with very critical info (1) you have an air/fuel problem, or (2) you don't have an air/fuel problem. At least you would know to concentrate on other areas.

I wish your problem could be solved as easily as with a manifold swap too. You can always borrow one from somebody & give it a try, but I wouldn't go out & buy one until after I tested the theory with a borrowed manifold. If we lived closer I'd let you borrow my Holley Strip Dominator. Surely one of the OC guys has a torker you can borrow.

We are talking about 2 "possibly" unrelated issues, so lets make that clear, (1) your motor is not producing the power that we expect from it (2) your motors torque curve drops like a brick above 5650 rpm. Your peak torque, at 4000 rpm, is not what I would expect, which is why I say the issues "may" be unrelated.

Regarding issue #1, ring seal is very important, if they don't seal properly, then you'll never achieve the bhp numbers you are expecting. On the other hand, Russ is quite capable of building a good short block, so I would lean towards ruling that issue out. If fixing problem #2 doesn't resolve problem #1, a leak down test may be called for. I can also guarantee you that your heads need some porting to achieve the numbers you and I both expect for your motor. The exhaust port demands most, but not all, of the attention. The roof of the exhaust ports has a bump that needs removal, and a flat surface that requires blending out to the exhaust flange. The whole exhaust port (sides, floor) also needs to be blended and "straightened out" dimensionally. I would also like to see at least 2 1/2" tubing between the collectors and the mufflers. I have no experience with the mind train exhaust system, if it will support more than 400 bhp or not. I like the Magne Flo muffler, like those sold by PI Motorsports, better than the dual glass pack systems I've seen. But liking something, and having actual dyno experience with it, are 2 completely different things.

Regarding issue #2, while a single plane intake WILL make bigger bhp numbers for you, I don't expect the Performer intake manifold to affect the motor the way you desribe, i.e. the drastic drop in torque above 5600 rpm. It will roll the curve off, but not that drastically. Thats more of a symptom I would expect from a fuel problem, an ignition problem, or a camshaft design issue. I'm just not familiar with the Comp retro-fit roller cam, so I am unable to say if that's normal for that cam or not. Dennis A's engine has the next size bigger Comp Cam and pulls to the mid 6000 range just fine. He's running C302 heads of course.

I've had engines exhibit similar charactersitics before, once it turned out to be a lifter had partially come apart, the push rod was still in place, it wasn't making any noise, but the guts of the lifter were laying in the lifter valley, that lifter wasn't opening it's valve! That one busted my balls for several days. More common was the old Holley running too rich syndrome. A rich carb will make the motor drop off like that. I've seen a 351C that wouldn't rev beyond 4800 rpm for that reason. But I wouldn't expect that from your "tuner" carb.

I would also not discount the older ignition coil, performance of coils does taper off with age & use, and aftermarket parts quite often do not have the longevity of oem parts. The MSD box could have a defect also. Ohming the spark plug wires would also be a good idea, especially the wire between the coil & distributor. You may want to monitor the voltage supply to the coil or ignition box while its being run on the dyno, the Pantera electrical system may simply just be dropping the voltage to the coil or MSD box as the current draw increases. A method to diagnose that issue is to install a direct jumper between the battery & ignition using a heavy gage (12 gage) length of wire with alligator clips on both ends. Ignition issues are also something that can be easily diagnosed on a dyno with an engine analyzer.

One test you can run is to rev the motor in the driveway & determine if the motor hits a brick wall under those conditions (unloaded) or only on the dyno.

It's getting late Art, I'm running out of steam. I hope I've given you some ideas. Perhaps some of the other guys have ideas.

Your friend on the DTBB

Art,

Taking my daily look through eBay, I see there's a Torker on right now, finishing in less than 12 hrs and still at under $70 (for now at least).

At that price you could take the chance and resell it if its not for you.

http://cgi.ebay.com/ebaymotors/351-Cleveland-Edelbrock-...QQrdZ1QQcmdZViewItem

> David Berman had his motor dyno tested with an Edelbrock Performer adapted to
> work with his Blue Thunder heads, that motor made a tad more than 500 bhp, at
> around 6000 rpm, feeding a 408 cubic inches.

He'd gain a bunch by moving to a Yates intake.

> Your motor is making about 407 bhp at the flywheel, which is about all you're
> going to make using the cast iron 4V heads without porting & a good valve job
> (multi angle).

Dan Haynes made right at 500 HP on unported 4V heads on a high compression
351C. He'd have made more with porting but the heads are not the limiting
factor here.

> The primaries (header tubes) are 2" OD which I guess makes them 1-7/8's.
> The exhaust pipe from the headers to the four glass packs is about 2-1/4" OD
> so I guess you would call it 2-1/8". exhaust pipes running into four glass
> packs.

The primary diameter is too large, the collector too short and the exhaust
pipe too small. If your mufflers are too restricitive (and glass packs are
often among the worst), you won't see much benefit from header tuning.
Some exhaust system rules of thumb:

OID = SQRT (Ex_CFM * 1.27/FD)
CD = 1.75 * OID

where:

OID = optimal internal diamter (inches)
Ex_CFM = exhaust port flow (CFM) at 28" H20
FD = flow density (around 80 CFM/square inch @ 28" H20)
CD = collector diameter (inches)

Primary lengths between 24 to 36 inches (for bank separated 4-into-1
on V8's with dual plane crankshafts)
collector length between 12 and 20 inches good for 8000 RPM

Mufflers should flow 2.2+ CFM per HP (the point at which there is a 1%
difference between mufflers and open pipes), 500 HP requires two 550 CFM
mufflers

A friend tested his unported 351C-4V heads (Super Flow at 28" water, in CFM,
stock single-angle valve job and 5/16" Manley valves with an MPG port plate)
and at your peak lift, they were around 180 CFM without a pipe. Plug in the
numbers:

OID = SQRT (180 *1.27/80) = 1.69 inches
CD = 1.75 * 1.69 = 2.958

Most Pantera headers have collectors way too short (5 or 6 inches) with
too small ID collectors and exhaust pipes and way too restrictive mufflers.

> I am using Isky #8005-A valve springs. Lifters were part of Comp Cams K-kit
> for this cam.

Comps K-Kit includes the springs and lifters. For some reason you're engine
builder chose not to use the K-kit springs. Comps standard hydraulic roller
lifters don't rev well. The Crane link-bar lifters have proven to rev much
better and Comp has recently introduced their version of a link bar lifter
but I've not seen any test data on those. Much care must be exercise in
picking the springs and lifters when trying to get a hydraulic roller cam
to rev well with heavy 4V valves and 1.73:1 rocker ratios.

> Your motor is making about 407 bhp at the flywheel,
> I have a Holley 750 double pumper with mechanical secondaries.

In addition to the Performer intake being a wrong choice for your set-up, your
carb is a limiting factor. 100 HP requires 140 CFM based upon a reasonable
assumption for Brake Specific Fuel Consumption (BSFC). The BFSC assumption
keeps us from having to guess at volumetric efficiency. A 407 hp engine uses
an actual 569.8 CFM. 4 barrel carbs are rated at 1.5" Hg but that is way too
restricitive on a tuned engine. 0.7" Hg is a more reasonable pressure drop
(too keep the carb from being a limiting factor). Converting to rated carb
CFM:

Flow @ 0.7 In Hg = (CFM Rating @ 1.5 In Hg)/SQRT(1.5/0.7)
569.8 = X / 1.46385
X = 834 CFM flow rating required

> I'd let you borrow my Holley Strip Dominator. Surely one of the OC guys has a
> torker you can borrow.

I offered up a Strip Dominator, Blue
Thunder, Boss 351, and Torker for a dyno test but I don't think he's interested.

But what about PI?

Art,
I basically have the same cam as Dennis A's but the seporation is for webers lift is 613.
and my 180's are 2" with 3.5 collectors. and 11:1 cr
so I need to get mine to the dyno.
Thanks
Dennis D

Dan what about step tube headers?
I always thought that an 850 DP Holley was the best "Performance" carb out of the box. It is ok on the street but a 750 is crisper.

> But what about PI?

What about PI?

> Dan what about step tube headers?

They can approximate a tapered header well enough. First step same as the
port outplet size, last step the size required by the formula. This stuff
is best optimized by something like Dynomation.

> I always thought that an 850 DP Holley was the best "Performance" carb out of
> the box. It is ok on the street but a 750 is crisper.

Best depends highly what it's going on but the HP series and Demon carbs
flow more these days for the same venturi area.

Dan Jones

quote:

Originally posted by Daniel_Jones:
> But what about PI?

What about PI?

Well I thought you would never ask. I'd like some Apple Pi a la mode thank you.

Dan Jones

quote:

Originally posted by Daniel_Jones:
...He'd gain a bunch by moving to a Yates intake....

David's engine builder dyno'd the motor with both intakes, I don't have the figures before me, but the Yates intake made something like 40 bhp more above 5000 rpm. David did indeed elect to run the Yates intake. For every extra bhp the Yates intake made above 5000 rpm, the motor lost an equal amount below 5000 rpm. I would have selected the Performer personally. You probably know that about me by now.

quote:

Originally posted by Daniel_Jones:
...your carb is a limiting factor. ... X = 834 CFM flow rating required....

Good point Dan, I glossed right over the carb last night. I have witnessed the 750 Holley take motors into the 500 bhp range, and the HP series, which weren't around 20 years ago, will do even better. But I can't argue that you can probably bolt 40 bhp on by going to an 850 HP carb, especially on a 377 stroker motor. On the street I would advise Art to run the smaller carb. Isn't Dennis A runnng a 750?

quote:

Originally posted by Daniel_Jones:
...I offered up a Strip Dominator, Blue
Thunder, Boss 351, and Torker for a dyno test but I don't think he's interested.

From the "aluminum containmant facility"! Show off! LOL......

Dan, you're the man! Your friend on the DTBB

Here is one more little bit of info regarding my car: I think one of my four glass packs is bad based on the sound. I can see most of the way thru all the glass packs and I see no obvious obstructions. It seems like a long shot, but could this be the problem or part of it?
Art

Yes.

You could be choking off 4 cylinders.

It would be like stuffing part of a potato in someones tail pipe. Not enough to kill the motor, but enough to limit how high it revs.

George

Thank you George,
Can any of you folks recommend some new mufflers that will flow well? Are there any to stay away from? The mufflers PI has for sale do look nice. I'm sure my neighbors would be ecstatic about new mufflers.
Art

quote:

Originally posted by george pence:
Yes.

You could be choking off 4 cylinders.

It would be like stuffing part of a potato in someones tail pipe. Not enough to kill the motor, but enough to limit how high it revs.

George

Thank you again Dan for all the good information,
Art

quote:

Originally posted by Daniel_Jones:
> David Berman had his motor dyno tested with an Edelbrock Performer adapted to
> work with his Blue Thunder heads, that motor made a tad more than 500 bhp, at
> around 6000 rpm, feeding a 408 cubic inches.

He'd gain a bunch by moving to a Yates intake.

> Your motor is making about 407 bhp at the flywheel, which is about all you're
> going to make using the cast iron 4V heads without porting & a good valve job
> (multi angle).

Dan Haynes made right at 500 HP on unported 4V heads on a high compression
351C. He'd have made more with porting but the heads are not the limiting
factor here.

> The primaries (header tubes) are 2" OD which I guess makes them 1-7/8's.
> The exhaust pipe from the headers to the four glass packs is about 2-1/4" OD
> so I guess you would call it 2-1/8". exhaust pipes running into four glass
> packs.

The primary diameter is too large, the collector too short and the exhaust
pipe too small. If your mufflers are too restricitive (and glass packs are
often among the worst), you won't see much benefit from header tuning.
Some exhaust system rules of thumb:

OID = SQRT (Ex_CFM * 1.27/FD)
CD = 1.75 * OID

where:

OID = optimal internal diamter (inches)
Ex_CFM = exhaust port flow (CFM) at 28" H20
FD = flow density (around 80 CFM/square inch @ 28" H20)
CD = collector diameter (inches)

Primary lengths between 24 to 36 inches (for bank separated 4-into-1
on V8's with dual plane crankshafts)
collector length between 12 and 20 inches good for 8000 RPM

Mufflers should flow 2.2+ CFM per HP (the point at which there is a 1%
difference between mufflers and open pipes), 500 HP requires two 550 CFM
mufflers

A friend tested his unported 351C-4V heads (Super Flow at 28" water, in CFM,
stock single-angle valve job and 5/16" Manley valves with an MPG port plate)
and at your peak lift, they were around 180 CFM without a pipe. Plug in the
numbers:

OID = SQRT (180 *1.27/80) = 1.69 inches
CD = 1.75 * 1.69 = 2.958

Most Pantera headers have collectors way too short (5 or 6 inches) with
too small ID collectors and exhaust pipes and way too restrictive mufflers.

> I am using Isky #8005-A valve springs. Lifters were part of Comp Cams K-kit
> for this cam.

Comps K-Kit includes the springs and lifters. For some reason you're engine
builder chose not to use the K-kit springs. Comps standard hydraulic roller
lifters don't rev well. The Crane link-bar lifters have proven to rev much
better and Comp has recently introduced their version of a link bar lifter
but I've not seen any test data on those. Much care must be exercise in
picking the springs and lifters when trying to get a hydraulic roller cam
to rev well with heavy 4V valves and 1.73:1 rocker ratios.

> Your motor is making about 407 bhp at the flywheel,
> I have a Holley 750 double pumper with mechanical secondaries.

In addition to the Performer intake being a wrong choice for your set-up, your
carb is a limiting factor. 100 HP requires 140 CFM based upon a reasonable
assumption for Brake Specific Fuel Consumption (BSFC). The BFSC assumption
keeps us from having to guess at volumetric efficiency. A 407 hp engine uses
an actual 569.8 CFM. 4 barrel carbs are rated at 1.5" Hg but that is way too
restricitive on a tuned engine. 0.7" Hg is a more reasonable pressure drop
(too keep the carb from being a limiting factor). Converting to rated carb
CFM:

Flow @ 0.7 In Hg = (CFM Rating @ 1.5 In Hg)/SQRT(1.5/0.7)
569.8 = X / 1.46385
X = 834 CFM flow rating required

> I'd let you borrow my Holley Strip Dominator. Surely one of the OC guys has a
> torker you can borrow.

I offered up a Strip Dominator, Blue
Thunder, Boss 351, and Torker for a dyno test but I don't think he's interested.

Thanks Dennis, I suspect we'll see some pretty good numbers from your engine.
Art

quote:

Originally posted by daleyracing:
Art,
I basically have the same cam as Dennis A's but the seporation is for webers lift is 613.
and my 180's are 2" with 3.5 collectors. and 11:1 cr
so I need to get mine to the dyno.
Thanks
Dennis D

George and friends,
Dennis Antennucci is running an 850 cfm carb. I would have thought that when I took my carb in to have it set up for the new stroker engine, they would do what was necessary to make it work well. I've heard of smaller carbs set up to flow like larger carbs, it didn't even dawn on me that I might not have enough carb to get the job done. When you mention another 40 HP from an 850, that sounds good. I just figured my carb would be correct for my application when I got it back from the carb shop. At this point, could I possibly gain 40 horses by switching to an 850?
Art

quote:

Originally posted by george pence:

quote:

Originally posted by Daniel_Jones:
...He'd gain a bunch by moving to a Yates intake....

David's engine builder dyno'd the motor with both intakes, I don't have the figures before me, but the Yates intake made something like 40 bhp more above 5000 rpm. David did indeed elect to run the Yates intake. For every extra bhp the Yates intake made above 5000 rpm, the motor lost an equal amount below 5000 rpm. I would have selected the Performer personally. You probably know that about me by now.

quote:

Originally posted by Daniel_Jones:
...your carb is a limiting factor. ... X = 834 CFM flow rating required....

Good point Dan, I glossed right over the carb last night. I have witnessed the 750 Holley take motors into the 500 bhp range, and the HP series, which weren't around 20 years ago, will do even better. But I can't argue that you can probably bolt 40 bhp on by going to an 850 HP carb, especially on a 377 stroker motor. On the street I would advise Art to run the smaller carb. Isn't Dennis A runnng a 750?

quote:

Originally posted by Daniel_Jones:
...I offered up a Strip Dominator, Blue
Thunder, Boss 351, and Torker for a dyno test but I don't think he's interested.

From the "aluminum containmant facility"! Show off! LOL......

Dan, you're the man! Your friend on the DTBB

I think the game plan should be to "fix" whatever is wrong with the motor now, i.e. the sharp fall off in power. Afterwards you can go on the hunt for more bhp. To do otherwise will not provide you the results you're expecting. If you indeed have an exhaust blockage, fixing that could very well boost the power numbers to were you expect them, with no further changes what so ever.

Your friend on the DTBB

Sounds like good advice George, thank you,
Art

quote:

Originally posted by george pence:
I think the game plan should be to "fix" whatever is wrong with the motor now, i.e. the sharp fall off in power. Afterwards you can go on the hunt for more bhp. To do otherwise will not provide you the results you're expecting. If you indeed have an exhaust blockage, fixing that could very well boost the power numbers to were you expect them, with no further changes what so ever.

Your friend on the DTBB

> But what about PI?

Ahh, you meant Pi :-) I forgot about that post and totally missed your
meaning. I saw PI and thought Pantera International and drew a deer in
the headlights blank stare :-)

> David's engine builder dyno'd the motor with both intakes, I don't have
> the figures before me, but the Yates intake made something like 40 bhp
> more above 5000 rpm. David did indeed elect to run the Yates intake.
> For every extra bhp the Yates intake made above 5000 rpm, the motor lost
> an equal amount below 5000 rpm.

Do you recall which Yates intake he used? Some don't work well out of
the box and need plenum work. I suspect they are designed that way to
permit custom work to allow them to be used on restrictor plate engines.
Also, a carb optimized for the Yates intake with annular boosters might
have been able to close the gap on the low end. Some of these tuner carbs
are pretty good these days but they have to be matched to the combo.
Sometimes the annular boosters help a bunch sometimes they hurt. It's a
completely differen type of carb but just to show the influence a carb can
have, I loaned a Strip Dominator to a buddy once to test a Predator (a.k.a.
Kendig) variable venturi carb once. With the variable venturi carb, the
big port Strip Dominator was better from idle on up than a much worked on
Offy Dual Port with spreadbore carb combo optimized for low and mid-range.
The Predator was able to meter fuel and low vacuum signals and overcame
the big open plenum of the Strip Dominator.

> I would have selected the Performer personally. You probably know that
> about me by now.

and I would have picked C302B heads with an IR intake :-)

> Good point Dan, I glossed right over the carb last night. I have witnessed
> the 750 Holley take motors into the 500 bhp range, and the HP series, which
> weren't around 20 years ago, will do even better. But I can't argue that you
> can probably bolt 40 bhp on by going to an 850 HP carb, especially on a 377
> stroker motor.

> On the street I would advise Art to run the smaller carb.

I'd rather him run a carb that flows 830+ CFM but meters as well or better
than a standard Holley 750. Proper attention to airflow can yield a carb
that flows more but atomizes better. A friend with a 372C, very similar
cam to the one Art is running (same specs but with XE lobes), and stuffed
4V heads with Parker Funnelweb just borrowed a Demon 750HP (I think he said
it flowed 815 or 830 CFM) and was amazed at how much better it was than his
750 Holley across the board. It was tuned on the dyno and I should be able
to get jets and power valve info should Art choose to go that route.

> Isn't Dennis A runnng a 750?

Dennis is running a tuner carb. I forget the exact specs but it flows quite
a more than 750. I don't have the numbers handy but it was in the range
where it needed to be.

> At this point, could I possibly gain 40 horses by switching to an 850?

I loaned my spare Blue Thunder to a Pantera owner in Kentucky (Jack Butler)
for a dyno test against an Offy 360and an Edelbrock Performer. The engine
was a 377 cube 351C stroker (0.600" solid lifter cam, 108 lobes, 6" rods,
offset ground crank, 10.5:1 compression, Willy's modified 950 HP carb, also
tested his old 650 Holley). Unfortunately, he ran all the tests with MPG
intake port plates, so I think that biases the intake manifold results but
not the carb results. The Offy 360 did very poorly, down 50 HP to the
Edelbrock. While the Offy isn't much of an intake, I think the port plates
hurt the Offy but helped the Performer which has smaller ports that match
more closely to the port plates. The Blue Thunder did best but the margin
between it and the Performer wasn't as large as expected, probably due
to the port plates. I loaned out my binders with the dyno sheets and Jack's
write-up but I believe the combo made a bit under 475 HP. Jack said the
Willy's modified 950 HP carb made a huge difference over the admittedly
undersized Holley 650 DP. IIRC, the carb change was equal to the difference
between the best and worst intakes (over 50 HP). You're starting with a
larger carb so I would think your results wouldn't be as dramatic but there's
power to be had.

> Here is one more little bit of info regarding my car: I think one of my four
> glass packs is bad based on the sound. I can see most of the way thru all the
> glass packs and I see no obvious obstructions. It seems like a long shot, but
> could this be the problem or part of it?

You need to get a look at Vizard's muffler tests. Even though you could
see straight through them, some of the glass packs were terrible when it
came to flow.

> Can any of you folks recommend some new mufflers that will flow well?

Walker flow rates their mufflers now using the Vizard suggested standard
pressure drop. Other manufacturers will tell you the pressure drop if
you call the tech line and ask. Look for Vizard's no loss exhaust article.
I'll see what I can dig up plus I'll ask a co-worker on his muffler dyno
test results. Due to competition, mufflers have come a long way in recent
years and the best ones can rival no muffler at all.

> Are there any to stay away from?

Quite a few, unfortunately. The other thing big cork in the exhaust is
likely your collectors. Most of the off-the-shelf Pantera headers lack
a meaningful collector and headers are much more sensitive to collectors
than primary pipe lengths. I bought my headers uncoated so I could
hack off the collector and put a proper one on.

Dan Jones

Dan did you ever test the Ford D1ZX single plane Doninator manifold?

You guys know more than I do... I remember the old saying.."If you can make it breath you can make it RUN" I run a 850 cfm on 409 ci so you are going to need somthing close to that for your stroker.

quote:

Originally posted by Daniel_Jones:
...I'd rather him run a carb that flows 830+ CFM but meters as well or better than a standard Holley 750. Proper attention to airflow can yield a carb that flows more but atomizes better...

You know me, I'll always opt for driveability when there's a choice to be made. But I agree Dan, if the new carb tuners can take the big carb and tune it so there are no compromises in drivability, then by all means, that's the way to go. In fact, that's BITCHEN!

> Dan did you ever test the Ford D1ZX single plane Doninator manifold?

No but that one looks very similat to a Weiand Xcelerator 4V.
I'd expect it's operating range to be similar to the Weiand
Xcelerator 4V.

Dan

Is that a scientifically accurate statement?

Dan,
You have mentioned the Blue Thunder high rise intake as being a possible solution to my problem. What do you think about the the Blue Thunder designed to fit under the screen of the Pantera, If you give it the green light, I'll probably just order the damn thing and move on.
Thanks,
Art

quote:

Originally posted by Daniel_Jones:
I loaned my spare Blue Thunder to a Pantera owner in Kentucky (Jack Butler)
for a dyno test against an Offy 360and an Edelbrock Performer. The engine
was a 377 cube 351C stroker (0.600" solid lifter cam, 108 lobes, 6" rods,
offset ground crank, 10.5:1 compression, Willy's modified 950 HP carb, also
tested his old 650 Holley). Unfortunately, he ran all the tests with MPG
intake port plates, so I think that biases the intake manifold results but
not the carb results. The Offy 360 did very poorly, down 50 HP to the
Edelbrock. While the Offy isn't much of an intake, I think the port plates
hurt the Offy but helped the Performer which has smaller ports that match
more closely to the port plates. The Blue Thunder did best but the margin
between it and the Performer wasn't as large as expected, probably due
to the port plates. I loaned out my binders with the dyno sheets and Jack's
write-up but I believe the combo made a bit under 475 HP. Jack said the
Willy's modified 950 HP carb made a huge difference over the admittedly
undersized Holley 650 DP. IIRC, the carb change was equal to the difference
between the best and worst intakes (over 50 HP). You're starting with a
larger carb so I would think your results wouldn't be as dramatic but there's
power to be had.

> Here is one more little bit of info regarding my car: I think one of my four
> glass packs is bad based on the sound. I can see most of the way thru all the
> glass packs and I see no obvious obstructions. It seems like a long shot, but
> could this be the problem or part of it?

You need to get a look at Vizard's muffler tests. Even though you could
see straight through them, some of the glass packs were terrible when it
came to flow.

> Can any of you folks recommend some new mufflers that will flow well?

Walker flow rates their mufflers now using the Vizard suggested standard
pressure drop. Other manufacturers will tell you the pressure drop if
you call the tech line and ask. Look for Vizard's no loss exhaust article.
I'll see what I can dig up plus I'll ask a co-worker on his muffler dyno
test results. Due to competition, mufflers have come a long way in recent
years and the best ones can rival no muffler at all.

> Are there any to stay away from?

Quite a few, unfortunately. The other thing big cork in the exhaust is
likely your collectors. Most of the off-the-shelf Pantera headers lack
a meaningful collector and headers are much more sensitive to collectors
than primary pipe lengths. I bought my headers uncoated so I could
hack off the collector and put a proper one on.

Dan Jones

Art I know that you are asking Dan and I don't mean to butt in, but T.S. I ran the Shelby version of that manifold. The Blue Thunder is a copy and "improved".
I found it to a restrictive manifold and made me want my Edelbrock Torker back.
I never blamed the intake for being flat under 4200. I always felt those were the iron 4v head characteristics.
If you deport the torker (like the one I have for sale) you make the engine noticably more responsive from around 3000rpm and up instead of 4000 to 4200 and up.
The Torker is a race manifold that is streetable.
It needs "gears" to run right.
If your local town decides to bring back trollies and needs grooves cut for the tracks, they will hire you to do it if you run the Torker. (Bet ya' don't know no trollies huh?)

Jerry Brubaker got his to fit below the engine screen, Blue Thunder, 14" round air filter, Corvette dropped air filter base, Edelbrock carb. It looked tight, but it was below the screen.

The Blue Thunder is available in a "flat mount" carb base version for cars in which the engine sits flat, like the Pantera. The Blue Thunder carb pad is very close to the same height as the Holley Strip Dommy.

Art, I like the BT intake a bunch, but with what Dan has written about the new crop of "tuner" carbs being able to make the open plenum intakes work as good as the 2 plane intakes, I would think the Holley Strip Dommy & a tuner carb would make the "best" combo.

To give you an idea how these things stack up in my mind, in the '70s & '80s I installed the BT intake with hydraulic cams, with power bands roughly in the 2000 to 6000 range. The Holley Strip Dommy intake was mated with solid lifter cams with power bands in the 3000 to 7000 range.

The Holley Strip Dommy & BT intakes are in my opinion the 2 best intakes for the cast iron 4V heads. They have the same carb pad heights, and will cost you about the same money ($300 to $350). One emphasizes the low end a bit more, one emphasizes the top end. But like everything else in the 21st Century, sounds like automotive technology has blurred the old lines.

Just please keep in mind, you have a problem to resolve with the motor dropping off like a ton of bricks at 5600 rpm that either intake is not going to fix.

your friend on the DTBB

Interesting, but isn't this all academic without an exhaust analysis or plug readings? Sounds somewhat premature to start swapping hardware without some baselines beyond the dyno.

> You have mentioned the Blue Thunder high rise intake as being a possible
> solution to my problem. What do you think about the the Blue Thunder
> designed to fit under the screen of the Pantera

It should be a good match to your set-up but I still think there's something
else like lifters/springs or ignition causing the sudden drop.

> I ran the Shelby version of that manifold. The Blue Thunder is a copy and
> "improved".

The Blue Thunder is based on the Holman-Moody high rise dual plane 351C
intake. I believe there were two Shelby 351C intakes (catalog?) One was
the same height as the Ford dual plane and looked to be a copy of the
over-the-counter Holley pattern versus of the Boss 351 aluminum intake.
The other was taller and carried the 351D-9424-D part number cast in at
the base of the #1 runner along with cast in Shelby Racetrack logo. That
one looked closer to the Blue Thunder and Holman Moody intakes.

> If you deport the torker

What is de-porting? Was this an early Torker or late Torker?
I've seen three different versions of the Torker (four if you count the
A331 version). The early Torkers had a cloverleaf plenum opening and
there was a tall version that looked much like an Edelbrock Scorpion.

Dan Jones

If you look at the A331 Ford Motorsport Torker, you will notice that it is basically a Edelbrock Torker with approximately 5/8" of the bottom of the port runners and the plenum filled.
That's what I mean by deporting.
That is the correct casting number on the Shelby.
The two versions are for Holley square bore and Holley Dominator.
The carb mountings were the only differences I saw.
In side by comparisons to the Ford Boss, the Shelby has larger volume and higher runner heights.
The Shelby vendors have always referred to the Blue Thunder as a copy of that manifold not the Hilman-Moody. Yes I saw the lower Blue-Thunder Pantera version.
I have to yield to you on that if you say so, never had a H-M.
Sure you can make all this fit under the screen but how restrictive is it going to be?
Just removing the air cleaner gives a one to four tenths improvement in the quarter.
That's an indication of signigfigant restriction. Feels more like 70 to 100 hp difference to me. It's a very noticable difference.

This may not relate completely but I thought it was interesting. Here are some Dyno runs where they compared the Edelbrock, Weiand and Holley. The engine is a 400 not a 351. It was a mild build up. It is hard to draw much conclusive from this group of dyno's but it is interesting:

http://www.tmeyerinc.com/400Fordpg3.htm

One thing to notice is the engine seemed to make more power after a couple of dyno's; aparently loosening up. This throws off the acuracy a bit.


To sum up a few things:
Weiand 384/450 (aprox hp/tq)
Edelbrock 390/450
Holley 390/446
Edelbrock Performer 388/460

That's n aproximate sumation. There were enough variable changes to make the figures +/- 5-8hp.

The main thing I see here with these intakes is their all within +/-5 Hp +/-5lbs tq.

My question would be would a blue thunder really make that much a difference?

Gary

Unfortunately Gary there aren't any similarities between the intakes in the Tim Meyer test & those under discussion. The intakes in the test are small port RV type intakes. For instance the Holley Tim Meyer tested is the "Street" Dominator, not the "Strip" Dominator. The Street Dominator is considered a joke to the Cleveland performance crowd. You can't give them away on ebay, whereas the Strip Dommy sells for $300 & up. The type of motor you would bolt one of those intakes to is not the same motor you bolt a BT or Strip Dommy to. Much lower rpm.

To answer your question the BT will make more bhp than Edelbrock's Performer 4V for the 351C or the oem Ford intakes, all on top, down low I wouldn't expect to see much if any difference. The BT is a free breathing high rise two plane intake that operates very well over a very wide powerband. But by its 2 plane design it is impossible for it to keep up with an open plenum intake like the Strip Dommy or Torker above 5000 rpm. The cool thing about the BT is that it doesn't give up as much power as the other 2 plane Cleveland intakes. Back in its hey day, it was the closest thing to keeping your cake & eating it too. It sounds to me that the Strip Dommy with a tuner carb actually achieves that now, a very wide range single 4 barrel intake system that makes even more bhp on top than the BT does.

All the modern hot rod stuff amazes me, the new heads, hydraulic roller cams, tuner carbs, inexpensive stroker cranks, bolt on fuel injection. It's all good. I can't wait to read what your new motor does on the dyno, I'm expecting good things.

My perception of things is influenced by the past, I get a chuckle from the younger guys who don't think 500 bhp is enough, and want more. Jeez! 500 bhp used to be a big, big deal.

I'd like to find out how your motor is going, but I don't want to steal this post from Art. I'll PM you.

Your friend on the DTBB

> If you look at the A331 Ford Motorsport Torker, you will notice that it is
> basically a Edelbrock Torker with approximately 5/8" of the bottom of the
> port runners and the plenum filled.

Gotcha. Here's a few pictures comparing the A331 and standard Torker:

http://www.bacomatic.org/gallery/album17

> That's what I mean by deporting.

If it matches an A3 port, I bet Dennis at PPC would buy it. He's
always on the lookout for the Edelbrock A331 intake.

> The two versions are for Holley square bore and Holley Dominator.
> The carb mountings were the only differences I saw.

There was also a low profile Shelby intake that looked like the Ford.

> The Shelby vendors have always referred to the Blue Thunder as a copy of
> that manifold not the Holman-Moody.

Many of Art Francis intakes are based upon the Holman-Moody tooling.
All three of them look very similar. I believe the Holman Moody intake
was introduced first. They may have cast the Shelby intake. There were
only a few places doing the casting (Buddy Bar, etc.). The Blue Thunder
came many years later, after both the Shelby and H-M were out of production.

> Yes I saw the lower Blue-Thunder Pantera version.

It's not so much lower as the carb pad is level.

> Sure you can make all this fit under the screen but how restrictive is it
> going to be? Just removing the air cleaner gives a one to four tenths
> improvement in the quarter.

That's a good point. If you go to a taller intake but end up restricting
it with the air cleaner, it's not going to buy you much. Likewise, giving
up the stock air cleaner case (with cold airducting) for an open element
that sucks hot air can be a losing proposition as well.

> The main thing I see here with these intakes is their all within +/-5 Hp
> +/-5lbs tq.

I don't think those results apply. Those are all intakes of approxiamtely
the same height and port size designed for low-mid range RPM on an engine
that is cylinder head limited. On a 351C-4V, the Performer is lower with
smaller ports and the engine is not cylinder head limited.

> My question would be would a blue thunder really make that much a difference?

On Jack Butler's 377C, there was something like 60 HP difference between
the worst and the best intakes. Also, in the Weiand thread, I mention
a drag test where the guy picked up 4 tenths with a manifold switch, that's
a big change.

Dan Jones

quote:

Originally posted by george pence:
Unfortunately Gary there aren't any similarities between the intakes in the Tim Meyer test & those under discussion.

I kind of thought so but it was an interesting comparison. Still makes me wonder if his problems are not more exhaust, possibly valves springs or other.

Gary

quote:

Originally posted by comp2:
...Still makes me wonder if his problems are not more exhaust, possibly valves springs or other. ...

agreed.

Dan, If it was an ignition problem, wouldn't I be able to hear it or feel it, like when an engine is obviously missing?
Thanks,
Art
[QUOTE]
It should be a good match to your set-up but I still think there's something
else like lifters/springs or ignition causing the sudden drop.

from page 3

quote:

Originally posted by george pence:
...I would also not discount the older ignition coil, performance of coils does taper off with age & use, and aftermarket parts quite often do not have the longevity of oem parts. The MSD box could have a defect also. Ohming the spark plug wires would also be a good idea, especially the wire between the coil & distributor. You may want to monitor the voltage supply to the coil or ignition box while its being run on the dyno, the Pantera electrical system may simply just be dropping the voltage to the coil or MSD box as the current draw increases. A method to diagnose that issue is to install a direct jumper between the battery & ignition using a heavy gage (12 gage) length of wire with alligator clips on both ends. Ignition issues are also something that can be easily diagnosed on a dyno with an engine analyzer.

One test you can run is to rev the motor in the driveway & determine if the motor hits a brick wall under those conditions (unloaded) or only on the dyno....

George,
Would it be safe to run the engine in the driveway up to 6200-6300 rpm(that is as high as Russ wants me to rev it)? I do have a 6500 chip in it as Russ recommended. I was thinking it would be nice to do it in the dark to see if any sparks were jumping. I have bumped up against the rev limiter a number of times so I know it will rev to 6500, if in fact the chip is doing what it is supposed to. When I have run up to the top of the rpm range, I have not been able to feel the drop off in HP. As a side note, my tach is way off when running up thru the gears, especially in first and second. Consequently, I don't pay much attention to it. The tach does seem to work normally if I'm not doing 0-60 or quarter mile kind of stuff. The problem with the tach is that it doesn't keep up. I can hit the rev limiter and the tach will show 3000 rpm.
Thanks again for all your help,
Art

quote:

Originally posted by george pence:
from page 3

quote:

Originally posted by george pence:
...I would also not discount the older ignition coil, performance of coils does taper off with age & use, and aftermarket parts quite often do not have the longevity of oem parts. The MSD box could have a defect also. Ohming the spark plug wires would also be a good idea, especially the wire between the coil & distributor. You may want to monitor the voltage supply to the coil or ignition box while its being run on the dyno, the Pantera electrical system may simply just be dropping the voltage to the coil or MSD box as the current draw increases. A method to diagnose that issue is to install a direct jumper between the battery & ignition using a heavy gage (12 gage) length of wire with alligator clips on both ends. Ignition issues are also something that can be easily diagnosed on a dyno with an engine analyzer.

One test you can run is to rev the motor in the driveway & determine if the motor hits a brick wall under those conditions (unloaded) or only on the dyno....

quote:

Originally posted by Art Stephens:
...Would it be safe to run the engine in the driveway up to 6200-6300 rpm(that is as high as Russ wants me to rev it)? I do have a 6500 chip in it as Russ recommended. I was thinking it would be nice to do it in the dark to see if any sparks were jumping...

As a first step I would like to see you identify what's causing the abnormal sound you hear coming from one side of your exhaust & repair that before going any further.

Yes its safe to rev the motor unloaded in the driveway, although the neighbors might not understand. Best way to deal with that is to invite the neighbor over to assist. If the engine is running poorly, bucking, misfiring, don't hold it there let it idle back down. Holding an engine running like that risks damaging the reciprocating assembly. Don't blip the throttle, just slowly depress the throttle and ramp the motor up. Keep your eye on the temp gage too. If there are arcs jumping around, you should see them at idle. After the exhaust is eliminated I'm suspecting low voltage causing the ignition system to loose steam as rpm increases. If that's the case, the motor should drop off, even unloaded. It won't misfire, just get weaker and reach a point where it can't rev any further. If you wired the ignition into the oem harness, feeding the MSD through the ignition switch, there is a very real possibility you have a big voltage drop that gets worse with rpm. If you have a voltmeter you can monitor voltage applied to the ignition while somebody revs the motor. As an alternative run the ignition directly from the battery with a jumper & see if the motor improves.

Troublehsooting over the internet is pretty frustrating. To do any good a person needs to be there, to listen to the motor, to put your hand on it & feel it run. The best way for you to resolve this problem would be on a dyno, with an exhaust analyzer stuffed up the tailpipe and an engine analyzer on the motor. A good dyno operator could pin point the trouble within 15 to 20 minutes.

However, you never mentioned wether or not Russ was informed of this trouble. If I were your mechanic, if that was MY motor, I would want the car into my shop pronto so I could diagnose it. I wouldn't want you listening to the advice of some cyber jockey on the internet to troubleshoot MY motor. Russ may feel the same way.

Like PTA mentioned, lets get your motor healthy before we start buying intake manifolds & carbs. Your power goal may be reached simply by getting the motor healthy.

Your friend on the DTBB

> If it was an ignition problem, wouldn't I be able to hear it or feel it, like
> when an engine is obviously missing?

It can be more subtle than a miss. I had one case that felt like a really rich
carb, just lazy. Turned out to be too much ballast resistance causing a weak
spark. Some ignitions introduce a bunch of unintentional spark retard at
higher RPM. First, I'd get one of those glass see through sparkplug style
spark testers and make sure I had a strong spark. Then you need to see if the
spark stays stable through the rev range. Have you checked the gap of the
plugs?

> I was thinking it would be nice to do it in the dark to see if any
> sparks were jumping.

If you do that, mist the area with water vapour.

> I have bumped up against the rev limiter a number of times so I know it
> will rev to 6500, if in fact the chip is doing what it is supposed to.

Rev very slowly through the RPM range and see if you can detect any sort
of surging.

> When I have run up to the top of the rpm range, I have not been able to
> feel the drop off in HP.

What did the dyno sheets say?

> The tach does seem to work normally if I'm not doing 0-60 or quarter mile
> kind of stuff.

Some styles of tachs are rate sensitive.

> I can hit the rev limiter and the tach will show 3000 rpm.

Hmmm. That may be a clue. Even rate sensitive tachs aren't that far off.
I wonder if the ignition is being compromised by the tach wiring or ???

Dan Jones

Has the issue of proper valve springs been hit on yet?

Gary

Art's mechanic ran Isky springs instead of the Comp Cam springs that Comp would have provided for their cam. I did question that way early, but to tell you the truth, I've put that one on the back burner assuming that Russ it too good of a mechanic to make a mismatch like that.

George

I have seen the graphs where the HP falls off like a rock so it was something I was curious about.

My brother had issues with his comp cams. He mic'd the last one. He called and asked what the tolorances were. He said they were out. He sent it back so Comp could measure them. They agreed but they said they weren't out that bad and that if he wanted tighter specks he needs a special ground. He then said well several have a low spot where the arc meets the flat spot. They measured and said yes it does. He said do I adjust lash for the low spot or the radius. They didn't know what say. They just told him again if he wanted to buy a special ground they could hold tighter specs.

Gary

As a first step I would like to see you identify what's causing the abnormal sound you hear coming from one side of your exhaust & repair that before going any further.

George,
I cut off the noisy glass pack, and I could feel no seat of the pants improvement in performance. My next step will be to replace my glass packs with the new PI stainless mufflers, unless someone has a better idea. I'm thinking that after I cut off all the glass packs, I'll take the car for a spin and see if there is any noticeable performance gain. I have also been keeping Russ posted on my trouble shooting efforts.
Thank You,
Art

Art,
Was reading your efforts to resolve your issue with power drop off, I came across your thread as I am in the process of doing more or less the same combo as your self,
I could not help but notice the part on the ignition, I have a fairly new ignition system in the Pantera now that is giving me the same problems you are having, the difference is, before I changed to this system I had a duraspark system that would let my 351C rev till it floated the valves at 7000rpm, That system developed a problem so I changed it out to a Mallory Mechanical Unilight, Petronix Flame Thrower Coil and a matching ballast resistor, It all worked great but as of 1000mi back it started to act like the problem you described! I believebecause parts changing can be so costly that a good dyno operator would be the answer as George has stated.

I to am looking at a 800-850 cfm carb,
Was just thinking back to 1983, had an 82 GT mustang "new" that I had pulled the little 302 out and built it to cobra specs with an off road cam & a holley 750 vaccume secondary's, met up with a beautiful yellow Pantera on the 91 freeway at Yorba Linda heading east, we got into it and reached 150+ when I started pulling ahead,not by much but the look on there faces was worth a million bucks and I still vividly remember to this day, the reason I say this is that carb on that motor was to big by popular opinion. You have built a respectable motor that will probably out perform the bigger cube builds but that 1 nagging issue needs to be resolved.
I have a specially ground cam from Crower that is good to 7500rpm that is not much different than your other than a dual pattern.
I personally don't think your cam is the problem.
I tend to be more of a chevy builder than the Fords and use alot of the info relating to chevy's to do my engine builds & tuneups, Very good success.
I am going to copy a build by "Joe Sherman, Engine Masters Champ" for a stroked 350 Chevy and apply it to my 351C to 377 stroker build, One of the things I really liked that he uses on a 600hp pump gas economy build, was a Crane Ignition system on crane's website.
Wish I was closer to give you a hand trouble shooting this.
My main plan is not to have more horse power but just be faster with a synconized combo of parts that work well together.

Mark