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
> 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.
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
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
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
> 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.
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
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 3quote: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
> 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
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
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
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
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
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