There are too many variables to use a math formula. Compression, ignition type, fuel used, which type after cooler or none at all, Piston type, crank material, main caps stock/billet/girdle, and the list is almost endless. Corvair Spyders used around six pounds of boost, Thunderbird Turbo Coupes 7-8, and Buick Grand National close to 10. With just four main bearings I would keep the boost on a Stovebolt down in the low end. Purposely built billet block/head blower engines the boost is only limited by the size of the owners testicles. One of the winningest "smoker" pull tractors was built from scratch to look like a John Deere but only the paint and decals were factory and it ran TWO HUNDRED pounds of boost. The main bearings were in a girdle and the one inch diameter bolts ran through the girdle, through the billet block, and out the top of the block to be used as studs for the custom billet head. The engine blew about mid-pull at the Whiteright Texas tractor pull and it was SPECTACULAR.
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