Have a 800 C.F.M. Holley model 4165 spreadbore carb I am thinking of rebuilding it . It has mechanical secondary's also 50 c.c. accelerator pump's. The carb has no choke . I believe the power valve is blown.According to holley this would increase jet size's by about 10 size's. The carb run's very rich.If I replace the pwer valve and install a backfire preventer kit will this carb give me descent performance in 454 Chevy?It is around 425 H.P. Any other ideas that would help me would be very helpfull.