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Discussion Starter · #1 ·
During my restoration I will get to the engine rebuild. I would like to keep things as close to factory as possible. The L79 had 11:1 CR. I am wondering based on all I have read, can I keep this 11:1 CR and run on 93 oct.? It is still not clear by the articles and comments I have read. Some say yes and some say no. I am confused. This same frame of mind seems to be the same with a couple of engine builder I have talked with. I have been told to install Aluminum heads and I should be able to keep the 11:1 CR. Please give me your input.
 

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What trans and gear are in the car?

If it's got deep gears and stick shift you'll probably be fine, just jet the carb a smidge rich and be picky about the brand of premium you run. If it knocks you ought to be able to tune it out with the distributor.

11 really is right on the edge, that's why some say yes, some say no. I sure wouldn't want 11:1 in a highly loaded truck application with an auto tranny. And you better be willing to tune the knock out. Sometimes that willingness it the only thing standing between working and not working.

Worst case you're adding a gallon or two of race gas to each fillup. How many miles will the car see? Is the 11:1 calculation with a thick head gasket or a steel shim?

Changing the pistons to 10.5 specs would sure be an invisible way to avoid issues without going to a non-original aluminum head.

Good luck!
 

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I think my 67 is 11.5 to 1 and I run it on pump premium, (non Ethanol when possible) and add octane booster. The only time I really have a issue is on hot days when the car has been ran for a considerable period of time. The octane booster solves the problem(pinging at light throttle). Some boosters are better than others, JB is a good one.
 

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Discussion Starter · #4 ·
What trans and gear are in the car?

If it's got deep gears and stick shift you'll probably be fine, just jet the carb a smidge rich and be picky about the brand of premium you run. If it knocks you ought to be able to tune it out with the distributor.

11 really is right on the edge, that's why some say yes, some say no. I sure wouldn't want 11:1 in a highly loaded truck application with an auto tranny. And you better be willing to tune the knock out. Sometimes that willingness it the only thing standing between working and not working.

Worst case you're adding a gallon or two of race gas to each fillup. How many miles will the car see? Is the 11:1 calculation with a thick head gasket or a steel shim?

Changing the pistons to 10.5 specs would sure be an invisible way to avoid issues without going to a non-original aluminum head.

Good luck!
The car has a 4 speed and 370 dif.
 

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Those gears ought to be deep enough to keep the engine's load light and minimize part throttle ping. If you do end up crutching things with an octane booster, look into buying 5 gallon cans of race fuel. Often times it's more cost-effective than the commercial additives. Good luck!
 
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