Will a sbc bolt right where the straight 8 was? If not how hard is it to put a sbc down in it. It's a 53 Pontiac chieftain
No it's not a direct swap. It's probably not the most popular swap around but you can bet its been done many times. You will not only need to swap the engine but also the trans, and probably the rear. All that along with converting to a 12v system, fixing any suspension/brake woes and cooling issues and you're off to a good start. If the engine in it now is still useable, I'd suggest working around that until you have more experience and can handle a much bigger project.
Why not use 55 to 60 Pontiac V8 . Use the same front motor mount and bolt it to your R-Type Hydro trany ,
Not many folks know this but Pontiac V-8s were run on test tracks in 1952, But GM was afraid the V-8s would hurt Buick sales.
If you must get rid of the straight 8 at least put something larger than a sbc to fill up the engine compartment,that sbc will look very small in there. I seen a early 50s Buick where someone done that swap and it looked hideous with that small engine in that larger engine compartment and looked to have room to add another sbc..
If you MUST put an SBC in (and not a pontiac V8), check out how volksjunky did his. He made a really nice bracket that mounts to the big crossmember. http://www.jalopyjournal.com/forum/showthread.php?t=550649&page=5 I put a Pontiac V8 in mine but the SBC is much easier in my opinion for mounting and running the exhaust.