Milling Heads, check my math please
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Joined: Aug 2008
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From: Lafayette, Louisiana
Milling Heads, check my math please
While I am waiting for my parts to come in, I am going over my plans repeatedly, weighing different options, making sure it's really what I want to do etc.
I'll spare the details of the proposed mild build and cut to the chase.
My goal is to get to 9.25 static compression. This will be perfect for the the rest of the components. I am starting with stock 1995 evolution that to my knowledge has never been opened up.
Stock compression is obviously 8.5:1
According to a table I found, using stock gaskets, removing .040" will give static compression of 9.07
This table also showed that removing .060", using stock gaskets, will give 9.39.
Obviously, going with the halfway point of .050", then the compression ends up being 9.23 which is almost exactly what I want.
Everything I am reading talks about removing the minimum and possibly having some problems with cracks etc. at .050" and beyond.
That being said, am I correct in thinking that all I need to do is get .040" removed then instead of a stock gasket, use Cometic .030" head gaskets and I will end up with something very close to the 9.25 that I am looking for.
Some things I find state that the original stock gasket is .040" thick but I also found some stuff about stock could be .060" Is the information wrong, or does it vary by model year? I find more information indicating that the original is .040" thick, so maybe the statements about .060" are incorrect?
Why the 9.25 you ask? It's what Andrews recommends for the particular cam I am going with.
I'll spare the details of the proposed mild build and cut to the chase.
My goal is to get to 9.25 static compression. This will be perfect for the the rest of the components. I am starting with stock 1995 evolution that to my knowledge has never been opened up.
Stock compression is obviously 8.5:1
According to a table I found, using stock gaskets, removing .040" will give static compression of 9.07
This table also showed that removing .060", using stock gaskets, will give 9.39.
Obviously, going with the halfway point of .050", then the compression ends up being 9.23 which is almost exactly what I want.
Everything I am reading talks about removing the minimum and possibly having some problems with cracks etc. at .050" and beyond.
That being said, am I correct in thinking that all I need to do is get .040" removed then instead of a stock gasket, use Cometic .030" head gaskets and I will end up with something very close to the 9.25 that I am looking for.
Some things I find state that the original stock gasket is .040" thick but I also found some stuff about stock could be .060" Is the information wrong, or does it vary by model year? I find more information indicating that the original is .040" thick, so maybe the statements about .060" are incorrect?
Why the 9.25 you ask? It's what Andrews recommends for the particular cam I am going with.
Road Captain
Joined: Aug 2012
Posts: 625
Likes: 102
From: New Albany, Ms.
Good Info
This site has a pretty acurate calculator for info your looking for. You may already use it. Would be nice if the shop your going to use could cc you heads.
http://www.bigboyzcycles.com/EVOComp.htm
Andrews also gives you a formula to figure out what what you need.
http://www.andrewsproducts.com/image...log-Page23.pdf
Good Luck.
Ride Safe,
Harold
http://www.bigboyzcycles.com/EVOComp.htm
Andrews also gives you a formula to figure out what what you need.
http://www.andrewsproducts.com/image...log-Page23.pdf
Good Luck.
Ride Safe,
Harold
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