dad has a coworker who bought a very nice 79 chev 3/4t pickup with a 400sb with 70k. it was kind of a dog so he put in the edelbrock performer package(rv type cam, lifters, springs, manifold and 600cfm carb) after all this he noticed very little difference to where he (albeit arbitrarily) guesses it gained him 15hp at best. gets about 5mpg with a 10ft camper and is a real dog up the passes. about 10 without. for as big an engine as it is and a decent amount of mods this seems pretty pathetic. hes pretty mechanically inclined too so i assume he did it right.
i recently put the edelbrock performer manifold and 1406(600cfm) carb on my 318. used to have the lo-po 2bbl holley setup. sure improved drivability but i didnt gain much for hp or torque. sure looks nice though and runs so good. in hindsight i might have just sprung for a quality 2bbl. im no ace engine builder but i also think compression is the key. thats what the early pre smog engines had over the later ones. if i ever have the heads off i think i will shave them and stop messing around. -ryan
i recently put the edelbrock performer manifold and 1406(600cfm) carb on my 318. used to have the lo-po 2bbl holley setup. sure improved drivability but i didnt gain much for hp or torque. sure looks nice though and runs so good. in hindsight i might have just sprung for a quality 2bbl. im no ace engine builder but i also think compression is the key. thats what the early pre smog engines had over the later ones. if i ever have the heads off i think i will shave them and stop messing around. -ryan