C5R heads, blown application?
Thread Starter
TECH Apprentice
Joined: Jan 2002
Posts: 320
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From: Nottingham, Notts, England, UK
C5R heads, blown application? I'm curious about these heads and wondering if anybody has machined the combustion chambers out to ls7 dimensions/volumes. Is there enough material to enlarge the chambers? I've done a search but can't find anything relevant or even if they're viable. I know the port locations are different on the intake. Thanks.
The C5R head chambers are 'naturally' 38cc. The most I have heard them being opened up to is 44cc. The heads require a 4.125 bore cylinder. Some of the biggest dish pistons I have heard are about -34cc. With a stock length crankshaft, that will ive you a compression level of 9.4:1 and a 388 CID displacement. You could definitely run a good amoutn of boost on that motor. Using a 3.75" crank, that will give you 10.1:1 and a 401 CID displacement. Still somewhat boostable. Goign with a 3.9" or 4.0", your compression level is get over 10.5:1 to 10.7:1. You can still run a S/C, but the compression level restrict the amount of boost you can run.
Keith
Keith
Thread Starter
TECH Apprentice
Joined: Jan 2002
Posts: 320
Likes: 5
From: Nottingham, Notts, England, UK
Thanks Keith, the c/r is what's restricting the boost on a 427 build I'm planning hence my wondering how big the chambers can be machined out. If I could get to 70cc like ls7 these heads could be of use to me. Either that or downstroke as you've mentioned.
Thread Starter
TECH Apprentice
Joined: Jan 2002
Posts: 320
Likes: 5
From: Nottingham, Notts, England, UK
Thanks Keith. So I take it nobody's looked to see how much metal is in the chamber walls? I drilled out an ls7 head and lets say there wasn't any excess material. I'm pretty sure my last build with ls7 heads got me down to a measured 9:1 with custom bowled pistons. I'd just like to go a bit lower for the next build. 
Boosted LS1, I sent you a pm for some people that built a 400ci. C5r race case with C5R head's and twin Turbonetics76mm turbo's. Not sure on the compression,but they can help with your questions!
