Ly6 turbo compression ratio help
10-18-2015, 06:05 PM
#1
Ly6 turbo compression ratio help
I'm in the middle of building a ly6 for the Tahoe, long story short I got a great deal on some forged mahle -26cc dished Pistons and I'm having a little trouble figuring out a good CR to be at... Here's a rundown of everything:
-26cc dished Pistons made for stock ls 3.622 stroke and .927 pins
Piston compression height: 1.314
Block deck height (stock): 9.240
823 heads: 70cc combustion chamber
Ls9 head gaskets 0.051 thickness
And whatever length rods I'm gonna use...
Here's the problem.....
6.100 rods give me -0.015 below the deck, which = 7.83:1 CR
6.125 rods give me +0.010 above the deck, which = 8.17:1 CR
6.200 rods give me +0.085 above the deck, which = 9.42:1 CR
I could use a little thinner head gasket 0.041 to bring compression up some... On the 6.200 rods and 0.041 gasket I would be at 9.62:1 CR.. I'm guessing this would be my best bet? Some input would be appreciated! Also, would the piston sticking above the deck on the 6.125 and 6.200 rods be a problem?
-26cc dished Pistons made for stock ls 3.622 stroke and .927 pins
Piston compression height: 1.314
Block deck height (stock): 9.240
823 heads: 70cc combustion chamber
Ls9 head gaskets 0.051 thickness
And whatever length rods I'm gonna use...
Here's the problem.....
6.100 rods give me -0.015 below the deck, which = 7.83:1 CR
6.125 rods give me +0.010 above the deck, which = 8.17:1 CR
6.200 rods give me +0.085 above the deck, which = 9.42:1 CR
I could use a little thinner head gasket 0.041 to bring compression up some... On the 6.200 rods and 0.041 gasket I would be at 9.62:1 CR.. I'm guessing this would be my best bet? Some input would be appreciated! Also, would the piston sticking above the deck on the 6.125 and 6.200 rods be a problem?
10-18-2015, 11:12 PM
#7
just gonna toss this out there... 6.2" rods put the piston above the cyl head height. its impossible. Look at your deck height and gasket thickness... What you will need to do is mill the heads down, but it seems you're kind of out of luck on this one. Thats a VERY big dish for stockish cubes.
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10-18-2015, 11:18 PM
#8
with a 6.125 rod and .041 gaskets with a milled 243 that comes in at a 60cc chamber you can achieve a 9.0 compression. that is very acceptable. A little low for my liking... but very doable. For reference, the LSA, LS9, and LSx376 are all that same compression
10-19-2015, 12:03 AM
#9
Formerly ScreamingL
Milling the heads kinda goes against whole strength in deck thickness
Spending money to save money on cheap stuff
By time you figure out a way to make those pistons work you would of been better off with a set of diamonds or wiseco
Spending money to save money on cheap stuff
By time you figure out a way to make those pistons work you would of been better off with a set of diamonds or wiseco
10-19-2015, 12:12 AM
#10
just gonna toss this out there... 6.2" rods put the piston above the cyl head height. its impossible. Look at your deck height and gasket thickness... What you will need to do is mill the heads down, but it seems you're kind of out of luck on this one. Thats a VERY big dish for stockish cubes.