So I have this '66 Electra 225 Custom. It had Pontiac 400cid engine and TH350 tranny, engine was in pretty bad shape, so I sold it but kept the tranny. Which engines will match with my tranny, 430 and 455 BBB perhaps? I already learned that 401 and 425 Nailheads would need Dynaflow, ST300 or ST400, and I am not gonna get new tranny at this point...
Welcome aboard! You're correct, the 400/430/455 Big Block Buick shares the same bellhousing bolt pattern of the transmission you have now. Just remember that the bigger the engine you bolt to the TH350, the less chance that trans has of living a long life. Devon
Like Devon stated, the Buick-Oldsmobile-Pontiac bell housing bolt patterns are the same, so any 67-76 Buick Big or small block will bolt up. The Nailhead had a different bolt pattern. Also, as Devon stated, the THM350 really isn't rated for the job behind a big block, unless you are going to be driving it like "Driving Miss Daisy". Heavy vehicle + Big block torque +Good traction = maximum stress on transmission. It is possible to beef up the 350 with parts, but you might as well just get a B-O-P THM400. It is more suited to the task.
Thanks for quick reply. I don't know what has been done to that TH350 but it has been in use with that late Pontiac 400cid for about a decade. And according to my friend, who had the car before me, it worked fine. Well, there is plenty of work to do with the body, before the engine.
It depends on how the car is driven. Also, not all THM 350s are the same. If it came out of a light car with a six or small V8, it has fewer discs in some of the clutch packs and has other light-duty components. If it came out of a 350 V8 with a four-barrel carb. it is a beefier unit then the one previously mentioned. There are members on this board that have been able to identify transmissions based on the numbers stamped on the case. Perhaps someone will jump in.
