Generation IV Internal Engine - Need help figuring compression ratio
03-16-2012, 07:03 PM
What i have is a 6.0 iron bored .040 using stock rods n crank n pistons are flat tops. Machinist said from his calculations the piston tops come above the deck .02 (this normal?) , heads are 243's plan on milling. 010 to clean them up n bump compression just a tad bit. Running a 224/230 .604/.609 lsa 112 and planned on using stock lq9 head gaskets. Whats my comp ratio gonna be? Any issues that stand out on this setup?
Thanks in advance
03-17-2012, 03:55 AM
Sorry .002 above deck
03-17-2012, 06:50 AM
Assuming you use a .051 gasket and your chambers are 62cc it should be around 11.3:1
03-19-2012, 04:54 PM
Not sure on exact chamber size whatever stock 243's are milled.010. Just wondering if its even worth doing just. 010 or go more depending on ptv and compression #'s. I wanna be able to run 93lq4 octane w/o detonation issues.
03-19-2012, 05:14 PM
The following is a URL that you can use to correctly calculate your compression ratio:
Another thing to be aware of is that an aluminum LS block grows vertically 0.012-inches from 70 degrees F to 190 degrees F. If your piston is 0.002-inches above the block deck cold, it will be 0.010-inches below the deck when the engine warms up.
03-19-2012, 06:17 PM
Its an iron block. N how much does each thousands take off of combustion chamber size
03-20-2012, 02:14 AM
About .0065/cc. So .010 will remove about 1.5cc's
03-24-2012, 03:59 AM
That KB silvolite link is great. Find your cam timing specs and plug everything in. Dynamic compression is the important thing here. I believe that the max recommended for pump gas is 9.5 dynamic. That's what my engine is, never a knock at 29 degrees timing on 92 pump gas. Yes, a stock engine is .005 piston above the block, yours is fine.
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