does a bored out engine require higher octane?

I'm looking at a 82' 720 that has a .40 bored engine and it says that it takes 93 octane. is this right? do you need to use higher octane fuel on bored engines? or is regular 87 okay? please help thanks.

i would run a higher octane on any built motor. Less chance of detonation.

Has it been bored just to clean up the cylinders or does it have a performance rebuild on it. If its stock and bored there is no need for 93 octane but if its hopped up it may require it. Try and get some details on the internals, heads compression, ratio etc.

mainly higher octane is for the the high compression ratios

my pup is bored over .90 and i can run 87 just fine, i have a header and a 38 weber

Octane you run is decided on several things.

Some being compression and ignition timing advance.

Originally posted by neurotic



mainly higher octane is for the the high compression ratios

x 2

Or if you are running a supercharger or turbo with high boost.

Your compression ratio will determine what octane you have to run. Boring it over will actually make your compression less if you use the same design pistons that it came with from the factory. After boring it out you more than likely will have to add a couple cc domed piston to bring the compression ratio back to what it was. I run 10:1 in my 357 SBC in my Nissan with aluminum heads.