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Old 03-17-2012, 05:27 PM
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408 sbc

Hey guys I need a little input but no jibber-jabber please
I picked up a 40 over 400/408 sbc that has a decent cam{don't have the specs}
and has the stock 487 heads 194/150 75cc
I have a set of 041 heads 202/160 64cc that I was thinking of using
the bottom end is all cast with speed pro flat-tops and an 040 head gasket
My concern is will the 041 heads give me problematic compression .Should I go to a thicker head gasket to lessen the compression or just put the fat heads back on
My peek rpm range will around 5500 This is for a mud truck
Thanks,Bob.
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Old 03-17-2012, 05:43 PM
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No "jibber-jabber"? I don't know if we can do that...

Find a compression calculator and figure out what you want, do a search here to see what's reasonable for c.r. Here's just one of many.

So far, with the 75cc heads, gasket and other info you provided, assuming 6 cc valve cuts on flat tops, you're at about 9.74:1, with 64cc heads you'll be at 10.48. This considering the piston is .025 in the hole.
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Old 03-17-2012, 06:26 PM
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408 sbc

Perhaps jibber-jabber was a rather poor choice of phrases, pistons are flush without gasket ,I guess its been decked , 4 v/relief on the pistons.
As long as I can run it on pump gas I'm o.k. with it but I'm concerned if I get into the 11's with my compression I'm gonna have problems with detonation?
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Old 03-17-2012, 07:15 PM
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I suggest to get Alum 64CC heads because it can handle higher compression then the iron heads. It lowers the BTU in the chamber therefore less heat.
Hope this helps.
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Old 03-18-2012, 05:45 AM
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408 sbc

heat is definitly NOT my friend with a 408 so I'm really interested in ways to keep the temp down .Since this is a zero deck block should I go to a 051 head gasket?
Thanks,Bob..
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Old 03-18-2012, 07:26 AM
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Cam specs would be helpful, as the intake closing point determines the dynamic compression ratio.

However, Peak rpm at 5500 rpms would require a small cam and will not tolerate much compression on pump gas.

You should consider setting up for E85 if you plan to use 64cc heads with a 408 with flat tops and a mild cam.
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Old 03-18-2012, 01:12 PM
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Zero deck, 64cc with a .051 gasket still nets you 11.25:1. Going much thicker on the gasket wrecks your quench.
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Old 03-18-2012, 01:39 PM
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Quote:
Originally Posted by 68NovaSS
Zero deck, 64cc with a .051 gasket still nets you 11.25:1. Going much thicker on the gasket wrecks your quench.
X2 this is about what i have with my 408.


Cole

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