Compression ratio
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Junior User
Joined: Jun 2003
Posts: 72
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Compression ratio
Anyone know what the highest compression ratio you can run without engine knock with:
1) unleaded
2) mid grade
3) premium
I'm rebuilding a 312 and would like 10.5, which I'm almost positive would require premium. If I could get 9.8 to 10.1 without using premium I may go that route.
Thanks..........freezeplug
1) unleaded
2) mid grade
3) premium
I'm rebuilding a 312 and would like 10.5, which I'm almost positive would require premium. If I could get 9.8 to 10.1 without using premium I may go that route.
Thanks..........freezeplug
Posting Guru
Joined: Jul 2001
Posts: 2,119
Likes: 2
From: Southern New Hampshire
Compression ratio
Thats a loaded question but with a .010 cleanup cut on ECZ-C heads on a 60 over & decked 292 I can run regular. It is for that reason I didnt use the ECZ-G or similar heads.
Now, I run 10.5:1 in a 396 Brand C and can retard enough to run OK on 89 octane; if I retard more to use 87 it doesnt run good at all and starts to overheat.
I also can drive about 20 miles North and get a better grade of 93 gas (less EPA crap) at the same price as 89 here so I often do that and run the proper advance.
Now, I run 10.5:1 in a 396 Brand C and can retard enough to run OK on 89 octane; if I retard more to use 87 it doesnt run good at all and starts to overheat.
I also can drive about 20 miles North and get a better grade of 93 gas (less EPA crap) at the same price as 89 here so I often do that and run the proper advance.