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Low Compression Street Engine's & Tuning Techniques Idea's...How Too's on low compression Engines.

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Old 11-17-12, 05:26PM   #1
76GrandPrix
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Default Stump puller cam

Does anyone have experience with SD performance's Hyd roller "stump puller cam" with the 230/236dur and .567/.578 lift with a 112 lobe separation specs? I'm currently running a Comp XR276HR with a 110 lobe separation, .502/510 lift 224/230duration and the 995-16 valve springs. My overall compression of 8:1. I have a 455 bored .045 over, RARE RAM AIR III 2.5 ported manifolds,1.6 ratio roller rockers, Q-jet, and a performer RPM intake. I dyno'd at 305hp 352tq at the wheels, but have a very sluggish torque curve.
Does anyone think I could benefit from this cam swap with 8:1 compression? What I'm reading a 112 lobe separation is better for cast manifolds for power than the 110. I plan on turboing this and think this might be a better cam. Here is a link to the cam and my previous post.

http://www.sdperformance.com/viewPro...productID=1815

http://www.pontiaczone.com/forum/showthread.php?t=27883
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Old 11-17-12, 08:42PM   #2
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Dont know about with a turbo, but i know exacly what it does in a N/A 462 and its not that impressive.
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Old 11-17-12, 08:48PM   #3
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Any advice on a roller cam with ported 6x heads and cast manifolds?

Last edited by 76GrandPrix : 11-17-12 at 09:07PM.
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Old 11-18-12, 02:04PM   #4
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So I found an article on almost an Identical build to mine withe the same cam, heads combo. They just used holley / headers / torker II instead of perf rpm and 1.65 rockers instead of the 1.6 and they had slightly more compression. I Don't think my drive train could eat 180 hp. I did not degree the cam when I installed it but something must be fishy with my setup. Mine liked 36deg timing and they only used 32. Plus my peak torque was in at 4100 almost 600 more then there test. Any help on this is appreciated.


http://www.highperformancepontiac.co...o/viewall.html
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Old 11-18-12, 06:32PM   #5
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where to start? Comparing LIKE combinations can lead a guy to pull his hair out. There are so many variables, there is no telling how they can combine to give one combo a significant edge over the other.

I DO believe there can be a valvetrain issue with those 995 valve springs. Using those springs with a FLAT TAPPET X/E grind, we ran into valve float at 5,000 rpm (ported E-heads, 1.65 Crower roller rockers, 5/16 .080" wall pushrods). A set of 985's allowed another 1,000 rpm and over 550hp. Do you know what your spring pressures are? If they are below 130/360, I would talk to Comp to see what they suggest for a possible spring upgrade.

Extremely low compression is a performance KILLER for an N/A combination. You can try to crutch it as much as possible with aggressive lobe design cams, but it is what it is.

For your combo, the most straight-forward addition would be a mild custom ground solid roller with a tight lobe separation. The tight LSA will close the intake sooner ( piston closer to bdc) and open the exhaust later (harnessing precious cylinder pressure longer). INCREASING DURATION would be a mistake.... you don't need to lose any more cylinder pressure.

If you feel your shortblock is well put together, then I believe the REAL answer is a well prepared set of heads that have the appropriate combustion chamber volume and intake port area for the displacement and rpm desired.

Now for a turbocharged application, obviously, the low compression would be fine. One thing some guys may not understand is, a turbocharger (or supercharger) would also benefit from a good set of heads. The misconception is that you can just turn up the boost and make up for a lacking cylinder head! You CAN turn up the boost, but, you will gain LESS from the increased restriction from a smaller intake path than you would with a bigger head and less boost.

I am not a supercharger guru by any means so be sure to talk to someone that can give you some specifics regarding your planned combo.
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Old 11-18-12, 09:00PM   #6
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Thanks for the info paul. Comparing is driving me nuts, I bought the cam and springs back in 2000 and the car always has had 18inchs of vacuum but had to have the idle at 1200 rpm because when went into gear it had a hard time idling with any less. Everyone says it should idle wonderful. I've had two sets of 6x heads on it with 9.5cr and 8.1cr and it idled same. Different carbs and ignitions. This has been my toys since I was 14 back in 1997. I just freshened it up two years ago and the dyno results seem low to me. I know theres tons of factors on that also. I'm just wondering if my manifolds and cam don't work together well killing the power. I just don't care for headers since I already have these
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Old 11-18-12, 10:09PM   #7
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Parts that may work in one combination, may not work in another. Those manifolds and cam are both good for a solid 450 or more.

That 550hp combo i just mentioned in the last post.... that used oversized RARE round port manifolds.

It's possible your cam is severely retarded.

Good luck with your combo.

Paul
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Old 11-18-12, 10:27PM   #8
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Thats what I was thinking because of the poor idle. I'll have to get around to degreeing it this winter. Thanks for the insight
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Old 09-13-16, 11:51AM   #9
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The power you are making is in line with your combo, I calculate you have about 390hp and 445tq at the flywheel
Since you are Goin to turbo the engine concentrate on the combo you are going to use, at 8-1 it's no surprise it's a dog!
Will a bigger cam make your engine have more low end? No not at all.
Stump puller likes at least 9-1 compression with iron heads, it does not use xtreme energy lobes!
550hp and 550tq with an xe274 and Ram Air manifolds even with bad ass E-heads, 10.5:1 and ported rpm is still a bit "of a stretch" IMHO
I get 565-575hp at 585-600tq with my little 470 hydraulic roller setups, 325cfm E-heads, 10.2:1, fully ported Rpm intake 1" spacer, 235-245 @ .050 cam .640in .643ex 112lsa 110ilc, custom 1000cfm 4150 carb, and hooked SC Headers, with my fully ported oversized manifolds I get 535-545hp and 565-575tq on 92 octane pump gas,
This whole time I could have been making similar power with a 535 lift flat tappet cam and manifolds?
I guess all that hard work and roller cam is a waste of time! Lol
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Old 09-13-16, 01:18PM   #10
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Once you have a FTC go flat on you it will show how nice a hyd roller cam can be.Tom
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Old 09-13-16, 09:08PM   #11
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Never had one go flat
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Old 09-13-16, 09:44PM   #12
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I have and it cost me a total rebuild on a fresh engine.SUCKED!
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Old 09-14-16, 10:56AM   #13
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Good cam I designed that cam 16 years ago and sold a bunch of them. Since then, the specs have been picked up and used by others. But would go with the 110 LSA with your compression.
FWIW; Have installed that 230/236 cam in a bunch of 455's with the ported 6X heads. One ran into the low 12's in a 4400 lb Pontiac Catalina.
Also have used this cam with nitrous on a 110 with great results.
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Old 10-24-16, 11:44AM   #14
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" it does not use xtreme energy lobes! "

Not to muddy the water, but just a fwiw tid bit.....

Dave Bischopp actually sells two similar cams, one he calls the "revised Stump Puller". It use XE lobes.

Grind# P8 3194 / 3196 HR112+5

( follow Pauls advise and check your spring pressure )


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