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I will be doing a little surgery on my 351C this winter as I suspect I have a compressed lifter (I have always had a "ticking" noise/ hot or cold, typically at lower RPMS. Since I will be taking the intake off, I was considering replacing it. I may also replace the cam, as the one I have is pretty "mild" and I'd like something with a little more PUNCH. Here are the specs on my engine (reported by previous owner):

4-Bolt D1 Block
Boss Rods
Boss 351 Heads (D1-2X)
SpeedPro 0.030" over 10:1 Pistons (Boss design)
Crank cut 0.010"
Crane 272H10 grind cam
Crane Gold Roller Rockers and roller lifters
700 CFM Holleyw/Mech Secondaries
Edelbrock 4V Performer Intake
Headers with 2" Stainless Mufflers (similar to PI Power Packs0

DynoJet Chassis Dyno showed:
312 BHP @ 5700 RPM
327 ft-lb Torque @ 4000 RPM

I think I have a solid base for a much higher HP engine and was thinking about a Blue Thunder Intake and changing the cam.

I would like a "streetable' engine with 400+ HP.

Any suggestions?

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Hi Swen!

How have you been? Missed your contributions around here. Hope all is well my friend.

I've got some questions for you regarding the motor:

Are you seeking 400 bhp at the flywheel, or at the rear wheels? At what rpm do you want peak bhp to occur?

What do you "mean" by a streetable engine? To me that means no more than a burble at idle with good vacuum in the manifold, and a powerband of 2000 to 6000 rpm. Is your definition of streetable any hotter than that?

By the way, the 312 bhp your motor makes on the chassis dyno is around 390 bhp at the crank. 400 bhp on the chassis dyno is equivalent to around 500 bhp at the flywheel.

cowboy from hell

Thanks for the quick response! Three kids under 12 and a SICK soccer schedule has sidelined my PASSION for a bit, but I'm hanging in there. Sometimes I get the urge to bail (sell the CAT) and all I need to do is FIRE IT UP and realize what a HUGE mistake that would be. Couple that with all the support I get from the Pantera community including my local club, Jersey Panteras and I'm STAYING!

You're on the money regarding "streetable". I ahve a very smooth idle now and wouldn't mind a little "lumpier" if I could add some PUNCH. Take a look at the specs on the cam grind; I think it is pretty mild, even for a street car. I am running an MSD 6 with a Rev Limiter (6000 RPM chip). I may be running a little rich as the car has always had a fairly strong exhaust smell. I re-piped the PCV system so that it is working properly which has helped. 2000-6000 powerband is fine.
> Boss Rods

What's the shape on the head of the bolt? I ask because a lot of previous
owners really have no clue and claim parts to be Boss which turn out

> Boss 351 Heads (D1-2X)
> SpeedPro 0.030" over 10:1 Pistons (Boss design)

Something wrong there. Boss pistons are domed and would give a much higher
compression ratio with the Boss closed chamber heads. Are the pistons flat
tops and forged?

> Crane 272H10 grind cam
> Crane Gold Roller Rockers and roller lifters

Something wrong there as well. Roller lifters are not compatible with
that flat tappet cam.

> Crane 272H10 grind cam

That is a hydraulic flat tappet cam with specs of 216 degrees duration at
0.050" lift (272 degrees advertised), 0.524" lift with 110 degrees lobe
spearation angle. I ran your combo through Vizard's cam selection guidelines
and got the following:

street performance 50 deg overlap, 107 LSA, 264 degrees seat duration
street/strip 70 deg overlap, 107 LSA, 284 degrees seat duration

with as much lift as is consistent with your reliabilty goals. The 107
degrees LSA will give you the rumpety rump idle you're after. By way of
comparison, the stock CJ cam has 46 degrees of overlap and the Boss 351
grind has 58 degrees. You'll likely want a cam somewhere between the
50 and 70 degrees overlap range above. There have been a lot of issues
with flat tappet cam lobes going bad causing many to go with roller cams.
If you do decide on a hydraulic roller, something like Comps 3315 lobe
profile would be what you are after. It's a medium aggressive lobe.
Have a friend running that in a 372C stroker and he is quite happy with

> Headers with 2" Stainless Mufflers (similar to PI Power Packs0

Be aware that a restrictive exhaust will upset a narrow lobe separation
cam more than one with a wider LSA. You need a good exhaust with 107
lobe separation cam. In a recent test of a mild street 408C, we lost
50 HP through the Euro GTS mufflers. Gained nearly all of it all back
with Magnaflows.

> Edelbrock 4V Performer Intake
> I think I have a solid base for a much higher HP engine and was thinking
> about a Blue Thunder Intake and changing the cam.

Out of the box, the Blue Thunder was a disappointment on the dyno.
Unported, it was down 40 HP to a ported Ford aluminum low rise dual
plane (Boss type with Holley carb pattern) on our mild street 408C.
After porting, the Blue Thunder outflowed the Ford intake by quite
a bit but we didn't get a chance to verify it on the dyno. The Holley
Strip Dominator did best. If you go with the Blue Thunder intake,
you may want to send it to someone like Dave McLain who can bring
the 4 bad ports up to match the 4 good ones. It's worth a bunch of

> I may be running a little rich as the car has always had a fairly
> strong exhaust smell.

Have an O2 bung welded into your header collector. It will allow
you to very easily tune the carb with a wideband O2 sensor. A tuned
carb will get better fuel economy, make better power and increase
engine life (no excess fuel washing oil of the cylinder walls, no
lean mixtures holing a piston, minimal carbon build up, etc.).

Dan Jones
Here's some of the issues involved:

To make generous power with a standard displacement iron head Clevo is easy & possible, but 500 bhp (flywheel) at 6000 rpm may be asking too much. I've seen good engine builders achieve 500 bhp at 6500 rpm, and 500 bhp at 7000 rpm is easy! Horsepower is (torque x rpm)/5252. Therefore to achieve 500 bhp (flywheel) requires the following torque at peak bhp rpm:

500 @ 6000 rpm = 438 ft/lbs
500 @ 6500 rpm = 404 ft/lbs
500 @ 7000 rpm = 375 ft/lbs

A standard displacement Clevo will produce about 440 ft/lbs torque at peak, with cams in the 0.600" lift range. This requires either a flat tappet solid lifter cam, or a roller cam (hydraulic lifter or solid lifter). The Clevo's combination of valve spring, rocker arm ratio and camshaft base circle size can open the valves in that range while maintaining reliability.

To make peak torque of 440 ft/lbs at 4000 to 4500 rpm and still have enough torque (438 ft/lbs) to make 500 bhp at 6000 rpm looks impossible to me.

To make as much power as possible in the 2000 rpm to 6000 rpm range (or any range for that matter) requires the following preparation:

>Good flowing intake system
>Good flowing exhaust system
>Well prepared 4V heads
>Camshaft ground to work best with the flow characteristics of the heads
>The best obtainable piston ring sealing
>Dyno tuned carburetor and ignition

Keep in mind that a peak bhp number is just a number, what is really important here, to provide a motor that has a good kick on the street, is crisp carburetion and a wide flat torque curve that is as strong as possible at low rpm and pulls hard to 6000 rpm. The further we design a motor to pull in the upper rpm range, the harder it is to maintain a hard pull at low rpm and the harder it is to maintain a decent idle and good drivability characteristics.

As far as intake manifolds go, I say use what you got. To make a broad spectrum generalization, out of the box, unmodified, any of the two plane intakes (Ford, Edelbrock or Blue Thunder) will work about the same below 5000 rpm, which is where the majority of your powerband is. The Blue Thunder will make a bit more above 5000 rpm than the others and is a good compromise intake providing two plane power below 5000 rpm and a good pull above 5000 rpm. The single plane intakes (Holley Strip Dominator, Parker Funnel Web or Edelbrock Torker) will make better power above 5000 rpm at the sacrifice of power below 5000 rpm. The Holley Strip Dominator is a long time favorite of Cleveland engine builders, and the Funnel Web is a good design that came on the scene more recently. The Strip Dominator or Funnel Web with a "designer" Holley in the 750 cfm range, would be a good combo for making the most torque over the widest streetable rpm range (idle to 7000 rpm). However with our more modest powerband goals of 2000 to 6000 rpm, the two plane intakes are only giving up power in the last 1000 rpm. So my advice would be to start with what you got, and spend the money elsewhere for now, you can always bolt on an intake later and compare it to what you were running before. I would rather see you spend the budget elsewhere.

You mentioned that your carburetor is running "fat" (rich). Getting the carburetor jetted properly would find a lot of horsepower and would make throttle response more crisp and seamless. This is a must do. You also mentioned your carburetor is a 700 cfm model, in my experience that is a bit small, 750 cfm would be more ideal. So with more power and crisper throttle response as a goal, it may be time to consider a new 750 cfm "designer" carb. Holley makes their own line of designer carbs, the "HP" carbs, I've read generally good feedback about the out of the box jetting of those carbs.

I don't have a clear idea of what your exhaust system is composed of, but if the tubing between header and muffler is only 2" OD, its too small. I consider the GTS exhaust system as a standard by which to judge other exhaust systems, the tubing of the GTS exhasust is 2 3/8" OD. I would advise you to upgrade the tubing on your exhaust system to 2 3/8" OD or 2 1/2" OD tubing. Free flowing mufflers are also needed, some are louder than others, some fit the Pantera better than others, they all have a different look, but that is an area you need to investigate. Dan's advice about installation of an O2 sensor bung is very good. It may come in handy down the road to help with tuning problems, or to upgrade to fuel injection.

As far as camshafts go, a custom ground cam is preferred over an off-the-shelf cam. MME is your source for a knowlegable Cleveland engine builder who can spec a good cam for your motor and your power goals. I recommend a roller cam for the reasons mentoned by Dan (lack of zddp in motor oil, cam lobe & lifter failure issues) so if there's room in the budget, that's the way to go. Off the shelf roller cams that fit your goals are the Crane #529551 hydraulic roller or the Crower #15480 solid roller. If a roller cam isn't in the budget, then my fall back off-the-shelf flat tappet hydraulic cam is the Comp Cams XE274. One last time, I want to emphasize, a custom spec'd cam will work better than these off the shelf cams.

This last recommendation is going further than you intended to go, but I bring it up just to give you something to think about. Cylinder head port work by an engine builder who understands using the 4V Cleveland heads on the street would be necessary when seeking max power. Low lift flow is weak with the 4V head. The head grinders will perform some port & bowl clean up, extra work on the exhaust port roof and the exhaust port short turn radius, and finally multi-angle valve seat work. However, before spending money on 4V head port work, its time to sit down and consider if an investment in other heads would have a better pay-off. Considering we're working with a standard displacement motor, our power band goals are 2000 to 6000 rpm, drivability and crisp throttle response are a big factor in being happy with the motor, camshaft lifts in the 0.570 to 0.610 range will be utilized, the power goals are 500 bhp or less, a set of small port heads would actually provide superior results. Food for your thoughts.

What ever you do, have fun with it!

cowboy from hell
Last edited by George P
Cowboy & Dan:
You guys have been a HUGE help. Thanks for the diagnostics on my build. Again, I have not had the engine apart, so with the exception of the heads, manifold, carb, and rockers, it is difficult to verify any of the internals.

I made a mistake on the exhaust specs. I originally had the stock ANSAs with 1-7/8" OD to the header collector. I went with a 2-1/4" inlet "Power-Pack" type muffler. The tubing from the collector to the muffler is 2-1/4". I saw results on the dyno in a gain of about 15 HP with these mufflers. Magnaflows, as Dan pointed out would probably be better.

My club has a Dyno Day in October. In preparation for this, I'll take Dan's advice and get the O-2 bung welded in. I am goinf to try to tune/ re-jet the existing carb first before making any carb changes. Getting the timing fine-tunes at the same time. Based upon the results of the "low-buck" mods, I'll stick with the Edelbrock 4V and if necessary, change the carb first, looking at the Holley HP line. Any feedback on the Barry Grant carbs? Some of the guys in the club are very happy with them.

Next step would be the cam change (looking at the Comps 3315 roller or Crane #529551.

Thnaks again boys!

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