Max compression ratio on 93?
Max compression ratio on 93? I'm trying to plan my next build. I'm currently running about 11.5:1 on 93, I know some guys run some crazy high compression ratios on pump gas and I'm curious what the safe limit is. It will be N/A for now and get a shot of Nitrous down the road. I cant see it being much over a 250 shot though.
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Joined: Jan 2015
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On my old car, i had 11:7:1 compression with no issues. But I made sure and always kept very, very good quality gasoline (Shell Nitro 93 octane) I was running speed pro pistons (I'll have to check the part number), 0.26 head gaskets, CC503 cam, 160* thermostat, stock heads and many many more mods.
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Joined: Dec 2010
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From: Maricopa, AZ
I'm at 11.8:1 on 91 octane in the Phoenix heat. No issues. The reverse cooling works as advertised.
But, you HAVE to take into account intake valve closing event timing too.
What cam do you plan on using?
But, you HAVE to take into account intake valve closing event timing too.
What cam do you plan on using?
I think it all depends on how you plan to use the car.
For drag racing and general driving where the motor doesn't already have a lot of heat in it when you're at full power, 12:1 is manageable on 93 octane. I ran 12.0:1 for 6 years on my heads/cam motor with never a detonation issue. BUT.....for open track sessions where it got very hot, I always mixed half 110 octane race gas.
For the new 383 build, I'll have 11.5:1, a 238 dur SR cam, and will run strictly 93 pump gas, even on the roadcourse.
For drag racing and general driving where the motor doesn't already have a lot of heat in it when you're at full power, 12:1 is manageable on 93 octane. I ran 12.0:1 for 6 years on my heads/cam motor with never a detonation issue. BUT.....for open track sessions where it got very hot, I always mixed half 110 octane race gas.
For the new 383 build, I'll have 11.5:1, a 238 dur SR cam, and will run strictly 93 pump gas, even on the roadcourse.
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I'm running about 12.5:1.....but then, I have a 246* solid roller cam.
I've never had an issue with heat, but I only put about 1500 miles a year on the car. So.....there's that.
Make sure your builder cams the engine appropriately and optimizes your quench (about .030" to .035") and you should make out OK.
Yep......looks good 
!!!
KW
I've never had an issue with heat, but I only put about 1500 miles a year on the car. So.....there's that.
Make sure your builder cams the engine appropriately and optimizes your quench (about .030" to .035") and you should make out OK.
!!!KW
Last edited by KW Baraka; May 25, 2016 at 03:31 PM.
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