Should i shave heads for more compression?
Should i shave heads for more compression? Well this is my combo, 370 iron shortblock, -14.9cc piston, Stock LQ9 heads with upgraded springs, ill be running teh GM MLS gaskets for the 4.000 bore, EPP blower cam 232/240 .595/.608 on a 115 LSA, D1SC with a 3.4 pulley 8 rib setup going to a SDCE within a couple months of teh car hitting the street, long tubes and probably a dual exaust. I was expecting a -9.6cc dish but got a biggger one but decided to stay with what i got because i didntw ant to wait months for anotehr shortblock and i believe in the people that built it. Only thing im worried about is the compression is gonna be mid 8s i believe (still have not found out exactly what it will be as im getting mixed results from different sources), instead of the seemingly ideal 9.5. Im looking to push this setup for all teh D1SC has in it and looking to get down around KP times. Can i shave these heads down enough to get me close to the 9.5 or at least low 9.X's? How much am i leaving on the table leaving it at the stock chamber size power wise? This will be going through a th400 and a 9" setup for the strip more then the street.
I get 8.8:1 with a MLS gasket if the piston is .010 out of the hole. I really dont think you will see much difference going to 9.5:1 to be honest. I am at like 9.2:1 right now. You will have to get to around 62cc on the heads and thats a lot of milling on an already thin head. Try it and see, you can always switch to some Darts or something with a small chamber if it doesnt work out but I dont think you will see much of a gain from upping the compression alone.
If thats teh case ill just leave it alone for now as i plan to upgrade the heads anyway. These are just something i got for a descent price to get my car up and running. Im sick of staring at 10-15G's worth of parts laying around not doing anything! These heads will b used to finish out this seasona nd probably sold over the winter as i upgrade to a dart or better. Just wondering if i should shave it down a lil before i throw em on since the heads are already off and gonna be checked for straightness at a shop anyway.
I think i got 8.6 when i did my math? Its a 4.030 bore and i forgot now how thick the 4.00 bore 6.0 gasket is and the -14.9cc piston, the stock LQ9 is a 72cc chamber i believe. Been a couple months since i did this math last. Every time someone calculates it its a different # for some reason lol! Not sure why im having such trouble figuring out where im at. I believe the piston is zero decked. Its a speed inc shortblock whatever they have em set to is where its at.
I am using a 72cc head, .054 compressed gaket thickness and .010 out of the hole I get 8.87:1. Zero deck gets 8.71:1. Dont know how people come up with different numbers. I get 8:1 with a -25cc piston and 72cc which checks out to what wiseco lists. Compression calculators are pretty basic..
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