Chevelle SE Build 04/17

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Re: Chevelle SE Build 04/17

Post by bracketchev1221 on Sun Dec 31, 2017 5:26 pm

Ok to clarify, the heads may be 165cc. This is the volume of the intake runner, not the flow in cfm. The test data you linked too is a flawed test because #1. It is on a 4.06 bore not a 3.73 bore of a 305. So put air into a bigger volume and it will flow more. #2. It has no exhaust pipe. Again, no restriction on the exhaust port.

I would however believe 2 things quoted. Brezenski heads got 165 cfm out of them at .400 lift. And that they basically stalled flow over .400 lift. Even the quoted test shows no real flow gains from .400 to .600 lift. The big gain from these heads are when they are put on 8.5:1 compression 350's and instantly are 10:1 engines.
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Re: Chevelle SE Build 04/17

Post by marx3 on Sun Dec 31, 2017 5:36 pm

Ohh you meant 165 cc runenr size.. okay.
I agree... the test dont compare to a 3.73 bore.
I am not stating that these heads will necesarily flow 185 cfm, but the test does show that they have decent potential. I wonder what 624 smog heads or 882's flow in stock form. I seem to remember seeing flow results once, that said mid 100's, maybe 160's cfm at .400-.500 lift
the 10:1 compression can only be achieved with a real thin headgasket, like a 0.20" one.
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Re: Chevelle SE Build 04/17

Post by zot on Mon Jan 01, 2018 11:34 am

Sorry...my post wasn't very clear about that.
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Re: Chevelle SE Build 04/17

Post by Joe73 on Mon Jan 01, 2018 1:42 pm

I wouldn't mess too much with head gasket thickness unless you measure how much your piston is in the hole. And take into account whether the block has been decked or not. Any deviation from .040 can cause detonation problems and you might not be able to get your timing where it needs to be for max performance. .040 is where you want to be, or very close.
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Re: Chevelle SE Build 04/17

Post by marx3 on Mon Jan 01, 2018 2:47 pm

didn't these engine come with pretty thin steel gaskets from the factory?
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Re: Chevelle SE Build 04/17

Post by Joe73 on Mon Jan 01, 2018 2:53 pm

Fel Pro site says this for the 1977-1993 305 head gasket. The 8510 PT has an opening size of 3.855 and compressed thickness is approximately 0.040. .040 is what to shoot for imho.
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Re: Chevelle SE Build 04/17

Post by marx3 on Mon Jan 01, 2018 3:39 pm

the "generic" headgaskets are almost always .039" or .040", but that don't mean these engines came with that compressed thickness from the factory, do you think?
I do belive I read somewhere ( from a trustworthy source ), that the compressed thickness of the head gasket in these old engines, was about .020" from the factory.

I have been diving into Pontiac and Oldsmobile stuff previously and for all I remember, the deck factory deck height on these two brands' old V8 engines, was also about 0.020".
I think there is reason to believe, that the factory deck height would be about .015-.025" in which case a .040 head gasket would put quench out of scale.
I measured my own stock 1979 LM-1 350 and the piston ( on one cylinder, only measured one ) WAS about .015" in the hole.
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Re: Chevelle SE Build 04/17

Post by Joe73 on Mon Jan 01, 2018 4:07 pm

Only way to tell is to measure and then order the correct gasket to make .040.
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Re: Chevelle SE Build 04/17

Post by marx3 on Mon Jan 01, 2018 4:09 pm

ohhh you mean to hit .040 quench? I think I misunderstood you the first time around :-) I thought you meant, that a .040 gasket should always be used no matter what
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Re: Chevelle SE Build 04/17

Post by Joe73 on Mon Jan 01, 2018 4:14 pm

Oh, ok. Yes, piston in the hole measurement plus compressed gasket thickness should total .040 . Thats a best case scenario.
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Re: Chevelle SE Build 04/17

Post by marx3 on Mon Jan 01, 2018 4:24 pm

totally agree. When I build my 350 with those 416 heads, I could either go 10:1 compression ratio with a quench right around .040" or go more pump gas friendly 9.5:1 and about .060" quench.
Went with 10:1/.040" quench and the engine seems happy.
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Re: Chevelle SE Build 04/17

Post by bracketchev1221 on Mon Jan 01, 2018 8:32 pm

.040 is also the minimum piston to head clearance you want with a steel connecting rod to prevent piston to head contact. I check my engines with no head gasket for piston contact. If it just clears I know with the .039 gasket I'll be good close to 8000 rpm.
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Re: Chevelle SE Build 04/17

Post by Limey SE on Tue Apr 17, 2018 3:29 pm

Well Now Winter is Almost over I HOPE anyways..... Have The Cam Kit thanks to some great Advice from Joe73 yet again ( you need to open a speed Shop Joe) LOL

Can not wait to get Busy on this SE yet again









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Re: Chevelle SE Build 04/17

Post by Roadcaptain S3 on Tue Apr 17, 2018 8:14 pm

Sold it. Working on the 73
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Re: Chevelle SE Build 04/17

Post by Limey SE on Tue Apr 17, 2018 8:22 pm

Man really ok How it coming then

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Re: Chevelle SE Build 04/17

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