Hey guys,

Well I have seem to of fallen upon a deal from a racer friend of mine. He's got a 358 small block with aluminum heads, steel crank, h-beam rods,J&E pistons, Single plane intake, Holley carb... He basically wants to sell me this "race" motor for cheap. The only problem is that the motor makes 13:1 compression. He said that if he was to do it again he would lower it to about 11:1 and run premium pump gas.

My question is, what would be the best way to go about lowering this motor to around 11:1? I know that I can go thicker on the headgaskets, but 2 points? That seems like too much to change by the switch of a headgasket. Are new pistons in order?


Thanks,
Joe Phillips

It would depend on the cc of the chambers and pistons in use. A forged piston dome can be machined away to lower compression, a thick head gasket could help. Depending on the heads, might sell them off and score something that would put the combo where you want. You need to find out the existing combo that resulted in the 13 /1 to come up with a game plan.

usually a thicker head gasket only compounds the detonation problem. (increased quench is not good)The cheapest fix(believe it or not) is to increase the chamber size. New bigger chamber heads or it may be possible to enlarge yours.The only problem with this is the cam choice. The cam for 13-1 wont work well at 11-1.

atleast the old heads should bring enough to finance a nice new set, and a cam swap isn't that expensive and relatively easy with the engine out of the car smile.gif

Just remember that you will need a rebalance if you do anything with the pistons.