[Chevy454]

Here's my experience with our L72, which is virtually identical to the L78...if you haven't extensively milled the block/heads and have a GOOD set of JE or CE pistons in there then you're compression is gonna be down and a load of octane will actually slow you down.

Our L72 had a stock rebuild by ourselves, and came in at a whopping 10.2:1 compression ratio when it was all said and done...I ran 91 octane (hightest we can get here in town) with occasionally a splash of 114. Our car actually picked up by only running the straight 91...especially if it wasn't just ungainly hot outside. With the low compression and high octane, we never could get enough heat in our engine...particularly in the combustion chamber, but we even had trouble getting heat into the block itself. And we weren't running in some extremely cold climate, it was Memphis in September. Anyway, I tried just straight 91, and the thing finally got some heat in the heads and picked up...you HAVE to have a certain amount of heat in your combustion chamber and block. So, if you've got a basically stock bigblock, a splash of some good stuff might not make optimal power, but it ain't gonna hurt anything...except maybe your ET...just don't go overboard with it.