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KirkEvil · 07-06-2017, 11:27 AM

LS1, stock 241 head ~67cc, stock .051" HG = 10.35:1scr
LS1, stock 243 head ~64cc, stock .051" HG = 10.73:1scr

Stock head gaskets are .051" to help with emissions to get a more complete burn of the charge. Going to .040" gaskets is best for a stock motor IMO to balance quench and clearance of pistons OOTH, then work out the chamber size to best fit DCR for your desired cam timing and fuel.

LS1, 72cc 317 head MAX milled to 65cc, .040" HG = 10.60:1 scr
LS1, 64cc 243 head milled to 62cc, .040" HG = 11.32:1 scr/ 8.77:1dcr (for Sir Beggs cam choice and 93 pump)

So with the 317 heads you would be leaving ~0.7:1 compression on the table. The rule of thumb for compression is ~5% per full point of compression, so 0.7:1 = 3.5%, and assuming ~450hp crank thats about 16hp. Plus the peace of mind that your heads are not milled thin and ready to give you a piece of their mind. Given you could still do some tricks with installed ICL or adding timing to make up some of the compression difference, but y?

07-06-2017, 11:27 AM	#709
KirkEvil 10 Second Club Join Date: Feb 2008 Location: Eatontown Posts: 1,647 iTrader: (11)	LS1, stock 241 head ~67cc, stock .051" HG = 10.35:1scr LS1, stock 243 head ~64cc, stock .051" HG = 10.73:1scr Stock head gaskets are .051" to help with emissions to get a more complete burn of the charge. Going to .040" gaskets is best for a stock motor IMO to balance quench and clearance of pistons OOTH, then work out the chamber size to best fit DCR for your desired cam timing and fuel. LS1, 72cc 317 head MAX milled to 65cc, .040" HG = 10.60:1 scr LS1, 64cc 243 head milled to 62cc, .040" HG = 11.32:1 scr/ 8.77:1dcr (for Sir Beggs cam choice and 93 pump) So with the 317 heads you would be leaving ~0.7:1 compression on the table. The rule of thumb for compression is ~5% per full point of compression, so 0.7:1 = 3.5%, and assuming ~450hp crank thats about 16hp. Plus the peace of mind that your heads are not milled thin and ready to give you a piece of their mind. Given you could still do some tricks with installed ICL or adding timing to make up some of the compression difference, but y? __________________ 1999 C5 FRC: 12.7@114 2008 TBSS: 12.48@108 2017 Silverado 2500 do you even lift breh?