compression ratio + pump gas

kittypancake said

So the octane rating system has changed since the "old days"? I had an Olds in high school that had 10.25 CR and ran fine on pump gas even under heavy loads. I guess I gotta try to get it into my head that what "used to be" + what "is" are not the same :(

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Also keep in mind if that was a factory compression rating, it was quite likely at least a point lower. I have checked a few now of various makes, and about a point lower than advertised is the norm. My 383 was rated at 10.0/1, with open chambered heads, but it took a milled set of closed chamber heads with bigger valves in them to get me to 9.9/1.