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CR and Octane

Bo Dillingham

Well-known member
Jun 23, 2001
Cortland, NY, 13045, USA
1965 crimson pearl (2002 cadillac?)
As a follow up to my question under "Rebuilding a 300 HP 327" which was answered very well by 59 Tom, I am getting several different opinions from friends about compression ratios. I have been driving small blocks for years with CR's in the 9-10.5:1 range on good old pump gas without a problem. Suddenly everyone is telling me that anything over 9:1 will result in catastrophies. Tom mentioned in his advice that the original 10.5:1 should be OK as long as I can get good gas locally. Can anyone expand on this? Is there a prefered brand or additive?
PLEASE NOTE: I may possibly be getting away with pump gas lately because the compression on my old vette is probably low; I haven't investigated it at this time, because my nephew has been driving the car for about ten years on the cheapest gasoline available. I intend to rebuild it this winter, and do not want to spend the time and money on a compression ratio that will not work on the street.
As usual, thanks again for all your help.

This might help you. (If I gave it to you before Bo, please excuse my forgetfulness. :eek:)

_ken :w
CR and octane

Thanks to both of you for the answers. I want you to know that I looked around for answers before I bothered the CAC, and I managed to find the Klotzlube.com site that has some good info on octane and mixing fuels. Unfortunately, like the website Ken gave me, it puts a 10.5:1 ratio next to an octane rating over 100.

I am confident, however, that the advice from Keith will work, and I will probably go with the 10.5:1.

Thanks again.
BTW, there is an excellent article in the Decmber issue of Hot Rod Magazine. ;)

_ken :w

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