If they are pricey engines, then why do most of them run in the 13's? I've read the rules carefully and no aftermarket parts are allowed. The class I'm talking about is cars that are very limited to what can be done to them. There's a 1973 340 duster that ran high 13's. And they change the pistons to help increase the compression ratio as they are allowed a 1.5 point increase in the compression ratio. I've seen the class you're talking about and it's different from pure stock drag racing cars, these guys even have to run the factory cam