I have located a 455 out of a '68 Olds 98 and I'm looking at putting it in my '79 Trans Am in place of the original 403. It's my understanding that most everything should be a direct swap but I was concerned about:
1) Hood clearance with the "Shaker" due to the taller deck height of the
455 vs. the 403
2) Will the 403 exhaust manifolds bolt on to the 455 heads allowing me to
avoid cutting up the existing 2.5" Flowmaster exhaust system?
3) The HEI in the 455 has no Vac advance, will the HEI distributor from
the 403 work in its place?
4) I've heard there are differences in the big block vs the small block
engine mounts?? Anything I should know about on that subject or will
the existing 403 mounts work?

Thanks in advance for any assistance.
1 Bad Bird

PS: The engine # is 396021 'F' and the head casting = 'C'. There are 3 different 4 barrel 455's listed for 1968, 365hp, 375hp & 400hp. Is there anyway to Identify which particular engine it is from that info?

Hi 1BadBird,

Welcome to TOC

1) Using “blueprint” dimensions, 455 is 0.93692” taller than the 403. Toronado carb flange was lower than the other 455, but I don't know how much.
2) Yes.
3) Yes.
4) Always use the mounts that came with the car.


Not an engine number, but a “casting ID” showing its intended use as a 455 block. The letters F and Fa, show two design revisions. Without records of those revisions, the letters are of little use.


Another casting ID. Again, not much use. Some were machined to use 2” (some for 2.07”) diameter intake valves.


The advertised 400 HP version would have been Toronado only.


No.

However, the engine number was stamped on the oil filler tube. The beginning one (or two) digits will identify the engine it was originally installed in.

Norm