looking to get 500-600rwhp this summer - what size injectors would work best. Would 42 sized work well - Mike

 

Injector sizing is based on flywheel HP, so you need to tell us what that will be, or what kind of drivetrain you are using, so we can estimate drivetrain losses. Then you need to tell us how you plan to get there, so we can estimate the brake specific fuel consumption (BSFC).... NA, S/C, turbo and N2O may all be different in this respect.

Lacking any detailed info, and guessing on the above you will be over 700 flywheel. For an NA engine, and running a conservative 85% max duty cycle on the injectors, 42's will not cut it, unless you run them at about 62psi fuel pressure. Running at the stock 43.5psi, you are looking at 50#/hr minimum.