1971 Chevelle SBC to a BBC [Archive] - Chevelle Tech

: 1971 Chevelle SBC to a BBC

Oct 13th, 09, 12:01 PM
I am removing a SBC from my 1971 Chevelle: I just bought a 454 BBC used. Can I use the flexplate from the 350? motor mounts from the 350? Motor comes complete with alt, carb etc. I know I need a new set of headers anyone know a good set of headers to use with a 1971 Chevelle with A/C and a 454? does it matter if the heads are sq or oval to match headers to a 454?

Any advise if helpful. Thanks

Oct 13th, 09, 12:06 PM
350 flexplate will not work on a 454, and I think you will need a new starter as well. Motor mounts should be fine. I don't think headers are different between rectangle port and oval port, unless you are looking at really expensive, high-end stuff.

Oct 13th, 09, 3:45 PM
Tom, I did this swap in my 71. Well I should say I did a sbc to bbc swap but I used a 402 and went from a 307.

Anyway I used hedman 1 3/4" painted steel headers. They fit like a glove you can drop them both in from the top if you wanted to. The disappointment here was the non hi temp paint that they come painted with. The mess it made when my fresh paint burned off was disconcerting. These hedmans came with a ball and socket flange and a 2 1/4" collector outlet. Header mfg should be able to answer your port to flange question.

If you had 350 originally in that car then 350-454 all use the same frame mount and motor mount combination. The combinations are "tall and narrow" or "short and wide"... something like that anyway.

I bought a new starter. I had serious heat soak problems. Even when cold it would crank slow. Maybe the 307 starter was intended for low compression motor or maybe it was tired.

Good luck man.

Oct 13th, 09, 5:00 PM
You need an external balance 454 flex plate, can reuse motor mounts and frame brackets. If the flex plates are the same diameter, you can reuse the starter. Oval or rect port refers to the intake port on the head, headers should fit either exhaust port. Good luck, Jim.

Oct 14th, 09, 11:16 AM
Thanks, for the 411 on my conversion. Very helpful.