Lower compression?
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Joined: Apr 2007
Posts: 51
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From: So Cal
Lower compression?
Could changing to a different cylinder head lower the compression significantly? I'm going to put a Procharger on and would like to lower the compression without putting in different pistons.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
IE ... to reduce a 540BBC's 10.4:1 down a significant amount to ... say ... 8.75:1 ... you'd need to increase chamber volume about 25cc. Assuming your combustion chambers are currently at about 121cc ... I can't think of any off-the-shelf heads w/chambers anywhere near as large as ~146cc ... maybe others can suggest one.
NOT what I'd do ... but a 0.125"-0.140" thick head gasket would probably get you pretty close.
If you're gonna pursue forced induction, me thinks you probably need to look at different pistons.
Racer
Joined: Oct 2004
Posts: 439
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From: Mukilteo Washington
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
Moving to forced induction takes more than just a lower CR if you're planning on running more than 10# or so of boost. I'd talk to the Procharger folks.
Pro
Joined: Feb 2004
Posts: 564
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From: Pittsburgh PA
The only way to drop the compression enough to run a supercharger with any useful boost is to have it at no more than ~9:1 C.R., and using a smaller cam without too much overlap or duration.
The short answer is, your engine is built wrong for running a blower. I'd suggest (as a much cheaper route) using nitrous, or dig out your water-cooled checkbook, as you'll NEED it...
The other option, for building a blown BBC, would be to build a 454 BBC, going with an all-forged bottom end, studs, fluidamper, blower (roller) camshaft, and have ~8.5:1 C.R. Basically, a mild combination, but stout. Add on the blower at your leisure, and you'll have at least 700HP at the tip of your toe, and be able to run it all day...
Last thing is, you can build it as funds allow, and simply drop it in when you're ready.
JMHO.
