LY6 10.7 to 11.0 Compression worth cost?
04-08-2016, 07:50 PM
#1
LY6 10.7 to 11.0 Compression worth cost? Hey everyone.
I am on the home stretch with my LY6 rebuild. It has 0.030" over LQ9 pistons with factory rods and crank. New rings, bearings etc. It also has a 231/236 .640"/.615" 111LSA TSP camshaft with 823 heads and a LS3 intake and nick williams 92mm throttle body. Also have 1 3/4 long tube headers into 3" collectors with dual 2 1/2 exhaust into dynomax mufflers.
Decks were cut so pistons are .002" out of the hole and I am using 0.040"x4.085" head gaskets so quench is right at 0.038"
Also the pistons had to have reliefs cut into them to clear the intake valves.
Here is my dilemma, most combos I see are at 11:1 CR and for a cam that size it seems fit.
With my combo I am coming in at around 10.7:1
Head CC: 68 (Is this correct or is it 70 for L92 heads??)
Piston CC: 2 (assumption for the valve reliefs)
Gaskets: 4.085" x 0.040"
Deck Clearance: -0.002"
Stroke: 3.622"
IF I have the heads cut to get the CC around 66-67 it would put me in the 10.8-10.95:1 range.
I am waiting to hear back from my machinist on how much ptv clearance he put into the combo when he fly cut the pistons since that will decide if I can even cut the heads or not.
He does not think the added CR is worth it for my size cam but is also not very familiar with LS engines.
MY big question is will it be worth the added cost to cut the heads another .012-.015" to get the compression up to 11:1?
**EDIT** When originally writing this post I was under the assumption that the facotry L92 heads were 70cc not 68cc.
Can someone please confirm. I have searched but some say 70 others say 68. Seems more people lean towards 68cc.
Thanks
Shane
I am on the home stretch with my LY6 rebuild. It has 0.030" over LQ9 pistons with factory rods and crank. New rings, bearings etc. It also has a 231/236 .640"/.615" 111LSA TSP camshaft with 823 heads and a LS3 intake and nick williams 92mm throttle body. Also have 1 3/4 long tube headers into 3" collectors with dual 2 1/2 exhaust into dynomax mufflers.
Decks were cut so pistons are .002" out of the hole and I am using 0.040"x4.085" head gaskets so quench is right at 0.038"
Also the pistons had to have reliefs cut into them to clear the intake valves.
Here is my dilemma, most combos I see are at 11:1 CR and for a cam that size it seems fit.
With my combo I am coming in at around 10.7:1
Head CC: 68 (Is this correct or is it 70 for L92 heads??)
Piston CC: 2 (assumption for the valve reliefs)
Gaskets: 4.085" x 0.040"
Deck Clearance: -0.002"
Stroke: 3.622"
IF I have the heads cut to get the CC around 66-67 it would put me in the 10.8-10.95:1 range.
I am waiting to hear back from my machinist on how much ptv clearance he put into the combo when he fly cut the pistons since that will decide if I can even cut the heads or not.
He does not think the added CR is worth it for my size cam but is also not very familiar with LS engines.
MY big question is will it be worth the added cost to cut the heads another .012-.015" to get the compression up to 11:1?
**EDIT** When originally writing this post I was under the assumption that the facotry L92 heads were 70cc not 68cc.
Can someone please confirm. I have searched but some say 70 others say 68. Seems more people lean towards 68cc.
Thanks
Shane
