Maximum Compression Ratio for Cam/Octane Combinations
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Joined: Apr 2006
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From: Lindenwold NJ
Maximum Compression Ratio for Cam/Octane Combinations
How do I calculate the maximium compression ratio I can use once I know my cam specs and the octane of gas I'll be using?
If the ratio is too high it will detonate, but you increase hp and efficiency as you increase the CR so I'd like it to be as close to the detonation point as possible.
Are there any rules of thumb I can use so that when I replace my heads I'll know what CR to request given a cam spec and octane rating?
I have a 224/230 .581/.588 cam and use 93 fuel.
If the ratio is too high it will detonate, but you increase hp and efficiency as you increase the CR so I'd like it to be as close to the detonation point as possible.
Are there any rules of thumb I can use so that when I replace my heads I'll know what CR to request given a cam spec and octane rating?
I have a 224/230 .581/.588 cam and use 93 fuel.
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Joined: Mar 2003
Posts: 12,094
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From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
With the intake closing point of 68.5 degrees as your cam has and 93 octane you can go as high as 11.5:1. I ran that cam with that compression and had no knock retard after tuning. 11.3:1 is a very safe place. I am in the process of replacing the cam with a larger 232/234 112lsa XER cam. It has a 70.5 degree closing point and since I will be running the same static compression, the dynamic compression will drop slightly.
