Miller says these 350 heads are the best, but there are still caveats. The 350 heads with a 5A casting offer a 68cc combustion chamber, the 6 head measures 70 cc, and the 7 head comes in at 69 cc. Olds heads are identified by a large number cast into them. One popular budget approach is to use 350 Olds heads to pump up the compression.

The production Oldsmobile 403 also suffers from the typical late-'70s handicap of lame 8:1 compression by way of large, 83cc chambers. This isn't an issue with a mild street engine, but he recommends his five-cap halo-style main cap girdle for any Oldsmobile 403 motor that will see more than 6,000 rpm.

Miller says when Olds opened up the bore on these '70s-vintage engines, it intruded into the main webbing area requiring larger areas around the main webbing that weakens the crankcase. The stock Oldsmobile 403 enjoys the benefit of a giant 4.351-inch bore diameter with a relatively short 3.385-inch stroke. We'll also assume that you would prefer to retain the stock torque converter and rear gear, which means being conservative with the cam timing. He mentioned that even an average street Oldsmobile 403 would benefit from the typical improvements involving heads, intake, headers, and cam timing without having to go too deeply into the engine.

Jeff Smith: We called our Olds guy, Dick Miller at Dick Miller Racing (DMR), to get his input.

Oldsmobile 350 flat top pistons