Thread: Sb388

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I am buying a 388 sb to put in a 67 chevelle an it is about a 680hp motor an it is 12 to 1 compression that is to much for pump gas , can I change cams and detune engine with smaller cam an put a thicker head gasket on it an get compression down enough to run on street with pump gas.

................nope

Assuming aluminum heads you'll need to get your compression ratio down to about 10.5 max, and you'll still be looking at 91/92 octane fuel.

Originally Posted by rspears

Assuming aluminum heads you'll need to get your compression ratio down to about 10.5 max, and you'll still be looking at 91/92 octane fuel.

.....nope ... cam may not play good and then theres intake . better start with clean sheet so you pick up a engine thats makes 680 HP ? was that the selling point .when i build a engine like this ring end gap not the same as many other things better to start with a clean sheet

Originally Posted by pat mccarthy

.....nope ... cam may not play good and then theres intake . better start with clean sheet so you pick up a engine thats makes 680 HP ? was that the selling point .when i build a engine like this ring end gap not the same as many other things better to start with a clean sheet

Pat, I wasn't commenting on the overall build, simply pointing out that his compression ratio is at least a point & 1/2 too high for pump gas, and he's not going to get there with thicker gaskets, which is never the answer to dropping compression.

Originally Posted by rspears

Pat, I wasn't commenting on the overall build, simply pointing out that his compression ratio is at least a point & 1/2 too high for pump gas, and he's not going to get there with thicker gaskets, which is never the answer to dropping compression.

no kidding go back to my first post ? nope... he came on here and i would go out on a limb????? say that he knew that the way the engine is now will not run on 93 so nope was posted on the way he was going after it . lower cr pistons cc dish or big cc chamber heads is the rigth way going after it may be better to sell the 680hp sbc and build a more friendly street engine bulid

Originally Posted by Ken1960

I am buying a 388 sb to put in a 67 chevelle an it is about a 680hp motor an it is 12 to 1 compression that is to much for pump gas , can I change cams and detune engine with smaller cam an put a thicker head gasket on it an get compression down enough to run on street with pump gas.

Hey Ken, saw this is your first post and forgot to welcome you to CHR! Hope that you don't let the third person replies put you off, and that you'll stick around and keep everyone here in the loop on what you're doing with the Chevelle. There is a wealth of good information you can glean if you stick with it and keep focused on questions you may have.

Ken, sure would be nice to see some specs on what's actually inside the engine in order for folks to make some suggestions on dropping the compression to a streetable number!!!!!

Oh yeah, welcome to CHR!!!!

Don't worry guys---it probably is only about 400 hp to begin with and will run fine as is------------

He suppose to send me build sheet I don't no all of the particulars about yet I do no the machine shop that built it an he is looking for build sheet also ,he stays very busy , I know he said it was a 10 second truck s-10 , I know the builder an he is good or I would not be interested and it is more than 400 hp , it's not my 1st rodeo

Welcome to the site Ken---hope you can stand a little bit of stuff--what kind of supercharger did you say was on that 388?

Welcome aboard Ken! Good to see you here.. you've made quite an entrance!

We're not a bad group.. like any family, we get a bit "dysfunctional" sometimes.. but don't hold it against us! We only want the best for you and your ride..

Dropping the static compression ratio with thicker gaskets will increase the squish dimension and may contribute to detonation more than if you kept the tight squish and higher static compression ratio. So says John Erb, chief engineer for Keith Black Pistons.

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I might need to move on to a different motor, maybe a Newer style engine I hear they got a strong bottom end .

Are you referring to an LS base platform?