lowering compression ratio
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TECH Enthusiast
Joined: Sep 2004
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From: Clarksville,Tn
lowering compression ratio As some of you might know I've been working on a roots blower setup for my car. The intake manifold and everything else I have fabbed up is working flawlessly but I've come to the conclusion that it just aint gonna run on the stock compression ratio. I've gotta get it lower. I know the easiest way would be to put thicker head gaskets on it but that will open up the squish area quite a bit and might make the detonation problem even worse. My only option other than that (with the exception of pulling the motor) is to hog out the combustion chambers. I was using a CR calculator and according to it I need to hog them out to about 73 cc to get it down to an 8.5:1. I know some aftermarket heads are 76cc, I'm just curious if I have enough material there to hog it out that much. Any of you guys that have had head work know what yer cc's were or know how far the stock heads can be taken to??
Have you tried alky injection? I think that is a better solution at this point. I honestly can not see you being able to remove that much material without hitting a lot of water or haveing it find water once it is running.
Thread Starter
TECH Enthusiast
Joined: Sep 2004
Posts: 595
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From: Clarksville,Tn
I'm running it on E85. I'm in the process of rigging up E85 injection above the blower to see if it will cool it down and cool the incoming air down too. I'd rather lower compression. How far can you take the stock heads?? If I could get it down to say 9:1 it would probably be ok. I'd do it with thicker head gaskets but I'm afraid opening up the squish area will just make things worse.
trickflow heads, i believe the chamber is bigger than the stock head and its made for supercharger application, someone correct me if im wrong but i believe they are 62cc combustion chamber. not really sure about it though, but iw ould look into it
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Originally Posted by NXSLT1
62 cc chambers won't lower it enough. I'm trying to avoid pulling the motor and rebuilding but that might be my only option.
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Joined: Nov 2005
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Originally Posted by NXSLT1
The bottom end is fine for no more boost than I'm running. I'm not an idiot, I know stock parts have their limits. If anything goes it will be the stock cast pistons.
