L78 & Today's Pump Gas?

[mockingbird812]

Hey Bill. Sorry I missed yr email on this subject. You probably know this, but the bottom line is you can run whatever octane that allows you to avoid detonation. Here are some things to consider:
What is the true comp ratio for the engine. An L78 is supposed to be 11:1, but manufacturing standards indicate in reality that may not be true (less). Also, if the engine has been worked on, the published factory 11:1 may have changed (different pistons, heads shaved, etc. In practice, I cut my 93 octane (available here in OH) with a quarter tank of 110 VP racing fuel (you are lucky to have access to racing fuel on the reservations out in Phoenix area - it ain’t cheap though). In a pinch, I have gotten away with just 93 octane, but I’ve listened carefully for detonation.

Tom (Wilma’s Boy) has has/had a few.....

[WILMASBOYL78]

Trying to cut corners on fuel quality for a vintage L78 engine is a risky adventure. I understand some folks may not have access to race fuel, but finding it is worth the effort. These motors crave octane and run best with an aggressive timing curve...no place for low octane fuel. We have 112-115 Sunoco five minutes away...it ain't cheap, but it smells great, burns cool and make the L78 come alive. In a pinch I use 100 octane av gas...

Bottom line...find the best fuel...it's worth the time and money

wilma