Okay... I know next to nothing about Pontiac engines. I know enough to know that they're similar in a lot of ways to Chevy SB and BB, but different in just enough ways to raise a few questions. These things came with TH400's. Are these the same TH400's that bolt to the Chevy blocks? If it fits a TH400, will it bolt to my 700R4? And what about the engine mounts? Is this a smallblock or more like a big block? I know there's no way to use my TPI on this monster, and I'd probably want to carb it anyway... Does anyone have any insight on this idea? Will this be fairly straightforward like dropping in a Chevy 350, or am I looking at a headache?

 

This subject comes up once in a while...

I can't think offhand of any internal parts at all that interchange between a Pontiac V8 and a Chevy V8, with the possible exception of lifters. Externally about all that's the same is the distributor cap and the spark plugs, and the factory carbs are similar in many cases though not the same.

The T-400s themselves are the same, but the case is different. The Chevy case has a Chevy bolt pattern, whereas the Pontiac case has the BOP (Buick-Olds-Pontiac) bolt pattern.

The exhaust is completely different. The motor mounts are completely different. The accessory brackets are all completely different. The Pontiac starter is on the driver's side, while the Chevy starter is on the pass side, so the battery has to be on the other side too.

Other than that, they're pretty similar.

As you might have guessed, it's not exactly a project for the novice engine-swapper. I suppose it could be done, like anything else; but it would be expensive and difficult at best, and a nightmare of incompatibilities and welding-torch work at worst.

If you want a bigger motor, get a Chevy 350 or 400. The 400, while a good motor in its own right, is no better than a Chevy small block; it weighs more; and there was never any provision made in our chassis to accept it. All in all it's a vastly more involved project than putting a different CID Chevy small block in it.

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"So many Mustangs, so little time..."

 

The only thing similar between these engines is the fact that they are both V8's...I installed a 400 into my 1987 T/A back in 1993. It was mechanically easy, but time-consuming. I used a Trans Dapt adapter for the 700R4, 2nd gen T/A motor mounts, and Ram Air exhaust manifolds.

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1989 Formula 350, 10.5:1 383", TFS heads, Comp Cams blower grind, TPIS Mini-Ram, BBK 58mm throttle body, Vortech S-trim 15 psi, DFI, 42# injectors, S/X fuel system, MSD ignition, SLP 1.75" headers, Flowmaster exhaust, MW Racehouse 700R4, Currie 9" w/3.50 gears, Jeg's sfc's, Jeg's lca's, S&W 8-point rollbar, lookin' stock street racer...

Best ET: 10.796 @ 125.8 on 16" Sportsmans...