10.6:1 Pump gas?
#4
05-04-2011, 04:10 PM
So craby, If I wanna go with LE2 heads, and I want to rebuild the bottom end, what pistons do you recommend that will get me the highest compression that I can run on CARB Country 91 octane w/10% ethanol? And what will that compression be?
Thanks.
And to the OP:
Good luck and kill Rustanks!!!
x01660
Thanks.
And to the OP:
Good luck and kill Rustanks!!!
x01660
#5
05-04-2011, 04:22 PM
Join Date: Mar 2009
Location: Tokeland, Washington
Posts: 21,672
i can run regular in my car. its only 10.6. i am planning on 11.5 with the 383. allot depends on the cam and supporting parts. heres something i got from elliott when asked about this. hope he doesnt mind.
LT1's WANT and NEED compression to run well.
Stock LT1's have 10.4 to 1. To make them run, we use a thin head gasket and mill the heads .035-.040" to get around 11.5 to 1 and a built 355 will like 12 to 1 compression. Aluminum heads, reverse cooling, etc all take heat away from heads and chamber so we need to run more compression and take advantage of this.
Do you need to pass an emissions "sniff test"?
What is the weight, gear and stall?
The 223/230 will seem milder in a 383 but if you have to pass emissions, we can't go any larger. If you do not need to pass emissions, the 383 will want a 230/238 cam to have the same drivability, power band, etc. The extra cubes just want 6-8 degrees more duration to be comparable to what a cam acts like in a 350/355.
The 383 may have better rods, pistons, etc so it can live longer at a high RPM also so if you have the gear, stall, etc, you might even wanna go bigger.
If going with the same cam for emissions, get a -10 to -12 cc piston and Fel pro 1074 head gasket to end up at 11.4-11.6 to 1. If you do not need to pass emissions and are using a larger cam like a 236/244 .608/.608 110 LSA, get a -5 cc flat top and run 12.0-12.3 to 1 compression. Lots of people doing this on 92/93 octane pump gas.
The engine builders that are used to old school SB Chevys with carbs and cast iron heads are talking people into building there LT1 with only 10.5 to 1 compression but these guys are never happy with the way the cars runs.
LT1's WANT and NEED compression to run well.
Stock LT1's have 10.4 to 1. To make them run, we use a thin head gasket and mill the heads .035-.040" to get around 11.5 to 1 and a built 355 will like 12 to 1 compression. Aluminum heads, reverse cooling, etc all take heat away from heads and chamber so we need to run more compression and take advantage of this.
Do you need to pass an emissions "sniff test"?
What is the weight, gear and stall?
The 223/230 will seem milder in a 383 but if you have to pass emissions, we can't go any larger. If you do not need to pass emissions, the 383 will want a 230/238 cam to have the same drivability, power band, etc. The extra cubes just want 6-8 degrees more duration to be comparable to what a cam acts like in a 350/355.
The 383 may have better rods, pistons, etc so it can live longer at a high RPM also so if you have the gear, stall, etc, you might even wanna go bigger.
If going with the same cam for emissions, get a -10 to -12 cc piston and Fel pro 1074 head gasket to end up at 11.4-11.6 to 1. If you do not need to pass emissions and are using a larger cam like a 236/244 .608/.608 110 LSA, get a -5 cc flat top and run 12.0-12.3 to 1 compression. Lots of people doing this on 92/93 octane pump gas.
The engine builders that are used to old school SB Chevys with carbs and cast iron heads are talking people into building there LT1 with only 10.5 to 1 compression but these guys are never happy with the way the cars runs.
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