Originally Posted by
Mike P
Glenn, you really don’t get into the high octane rating (113 to 115) unless you’re talking about E85 and to really see much benefit from the E85 you need to start looking at CRs starting around 12:1. E10 premium still only ranges between 91- 94 octane depending on where you are.
Aluminum heads of better design, camshaft profiles and (probably most importantly) fuel injection and timing that are computer controlled allow the newer engines to run higher compression like we used to back in the “good old days”.
If MrGody lived at a higher altitude (say around 4500 ft) and the car was never going to leave that general area I might be tempted to go a ½ to ¾ point higher on the CR, but LA is about as close to sea level as you can get. On a carbureted engine with iron heads I tend to agree with Roger about a true 9:1 being about the maximum compression you’d want to run on pump gas.
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