Just out of curiosity can anyone tell me the HP gains by replacing the old stlye "Log" 3 inch manifolds with center rise 4inch manifolds vrs. replacing the 3 inch manifolds with 4 inch stainles marine headers.

Thank you,
Cliff

What engines? If you are gonna swap them out, i'd go straight to a stainless marine, Gil, etc..Im guessing you have very early 80's 454?

Yes the motors are from the early 80's, actually they are 454's 330 TRS on a 81 Scarab Type S

Realistically, Unless you plan to upgrade the engines, I dont think you will gain that much from the upgrade with the 330HP engines. Now if you had the 400 cyclone motors, then i would say definintly go for it.

BTW, i have some sweet gaffrig old school mufflers that will fit your 3" tailpipes. They are the air actuated style. Only one pair but they are like brand new. Dont think they were ever used. No carbon at all inside...I'd sell them cheap, i have no use for them... Gaffrig still makes them i believe..