LOL. Those sound like Dairy Queen cams?:cool:

It seems like some of the expectations for the new heads are base from the running 4X heads. I have never heard of someone cutting a 98cc head down to 82cc. I know that is at least a .080” cut on the head surface, but probably in real life I think it would take just over a .1” cut to get most 4X heads down to 82cc’s. Maybe it is possible someone did that? Sure seems highly unlikely, I’m not sure the head gaskets would even seal up after a cut like that. The static compression of a 455 with speed pro’s and 4Xs is usually in the lower 9s.

I ran the numbers and came up with 216 cranking compression at 11.4 with the that cam in it. I added quick screen shot from Stan’s program for an estimate. Stan can do it properly if he wants. My guess the future combo will take about 96 to 98 octane running OTB KRE D port heads. Good luck with that. But it helps, I”ll hold your beer while you try this. :)

Big Mutha' Thumpr™ 243/257 Hydraulic Roller for Pontiac 265-455. Street/strip, needs 9.5:1 compression, 2800+ stall, intake, gears and headers, very rough idle. Distributor gear upgrade required.


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I noticed too that this new combination is getting the new evolution comp lifters. Those have only been out less than a year. So have you even ran that big thumper cam? Do you know what it will be like driving a cam with 95* of overlap?

I don’t think I can carry that much beer.

IVC = Intake Valve Close The Intake valve is not closed @ 0.050" lifter raise or 0.050" lifter raise plus a given number. This graph over time has been pretty close.

The Octane Req. has many variable and this is more of a guesstimate.

Stan

3/8 pushrod over kill for hyd roller IMO.Tom

9.5 or 11.5 what's a couple of points of compression amongst friends!

Yup, they work good in certain applications. However I don't think I'd try one in an engine that I was pushing the compression way up to test the pump gas limits.

95 deg overlap ! 216 cranking psi ! That thing will not be much fun on the street. Seems like a cam designed more to make noise than usable power.
Might want to give Tim Goolsby a call at Bullet. 662-893-5670 ext 102
X2 on no 3/8 pushrods. Not worth your time opening the heads up.

me too, I'll find out soon

sure it does :rolleyes:

[QUOTE=Jay S;6456924]I noticed too that this new combination is getting the new evolution comp lifters. Those have only been out less than a year. So have you even ran that big thumper cam? Do you know what it will be like driving a cam with 95* of overlap?

I have and I sure do.! same set up i ran for 5yrs / 15,000 miles. longest trip i took was 12hr 440miles damn near straight running ( had to stop for fuel a few times )
in the mountains of PA on a all day covered bridge tour with my daughters.
i had the regular lifters from comp but had to swap out for these because they had the same specs i did not need to change anything else.

of course it is.....:rolleyes:

Glad you already ran that cam and know what to expect.

Sounds like the new head combo is a done deal. Your not really asking us what to do, your telling us what your going to do.:beerchug:

Just curious what kind of times did the old combo run? Were the iron heads ported and if so what did they flow?

I was kind of under the impression it was the engine builders idea to run the 11.4 compression because he was "a race guy".

I have the same impression, the OP apparently has some concerns about it, but is going forward anyway. Lol

That's why I'm on this forum to learn. I had no idea 14.5:1 was pump gas friendly (stated in the race section) ...... I learned something. :)

I'm sorry I cancelled my subscription to Popular Hot Rodding.

Like Nike, "just do it".:)

[QUOTE=PAUL K;6457141]That's why I'm on this forum to learn. I had no idea 14.5:1 was pump gas friendly (stated in the race section) ......

Where can you find 14.5:1 pump gas? NASA? 😆

There has been a time or two when i saw a thumper cam in a engine or two on a dyno testing heads or intake so the center of attention was not the cam and the HP and torque was impressive to the seasoned operators much to my suprize

they are possibly overlooked / dismissed and underestimated due to its advertised sound effects

They are good cams in the correct application. Sometimes folks think they bleed off cylinder pressure due to the longer exhaust lobe. They actually due the opposite.... But you are correct they can make good power.

Agree, 3/8 pushrod is overkill.
We have been using Manton 5/16"- 0.118" wall section for years and their service and products are top notch.
And Smith Brothers which are good have them with a thicker wall. So does Comp.

http://www.mantonpushrods.com/Pushrod-Info.html

"Stiffness often trumps lighter weight when it comes to valvetrain design"

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