1972 Demon 340 engine mods

the factory rated them at 10.5:1 so you could build to that ratio and be NHRA legal for stock class style racing.If you start at 10.5:1 and perform a stock rebuild...ie square the deck,machine the heads,bore .030 you would be over 10.5:1 and be illegal unless you make other adjustments to reduce the compression back to 10.5:1.