Thread: 400 vs 455

Tweet

i have a 400 30 over trw flat tops xe 284 comp cam 72 cc heads with 995 valve springs 10 degree retainers heads ported all the way through performer rpm intake 750 mighty demon carb msd ign.heddman 1 3/4 headers through 3 in.ex i'm going to put heads cam intake carb ign.headers on 455 30 over with trw flat tops(not concern with compression)i was wondering what kind of gain i would see and any suggestion thanks

thanks for the help

wich 455 are you using? buick or olds? big difference! My wifes hot rod is a buick electra 225. She is a college professor so has to look civilized. It has a stage 1 455 with a smallish crane cam and edelbrock intake and a 750 holley avenger. At it's last inspection before we moved here it was getting 420 hp at rear end. It is a big heavy car but man will it move. The ac still works perfect and so does the cruise. I just had to swap the air ride out in favor of good gas shocks because of the cam. It was a vaccume operated air pump. Oh well. The exh is basicly stock too so it is a real sleeper. If you are looking for a real hot rod 455 though I hope you got one from a olds as they have a lot more performance parts available than buick does.

If I understand what you're saying, you want to put heads from a 400 sbc onto a GM 455 big block engine and you want to know if you will gain anything from it. I think all you'll gain is a lesson on incompatibility. If you're chaging heads the compression is very important and should be of some concern. It doesn't make sense to put heads from a smaller engine on a big engine. It usually wont flow as much air/fuel mix as the heads designed for it. That's probably why no one here had any experience with it.
AL