73 Ventura 455 Swap

[Misfire_455]

So I've got a 1973 Pontiac Ventura with the Pontiac BB 350 in it. I just bought myself a 455 short block and am in the process of building it up and am going to swap it in. I've got lots of info on the swap itself and know that it'll bolt in place of the stock 350, and that the stock tranny will bolt up to it but I've heard that the stock tranny won't hold up to the added torque of the 455.

Does anyone know of a tranny I can swap in that'll bolt into my ventura and up to the 455 and handle the additional duty?

[MagicRat]

What trans do you have now, auto or 3 speed or 4 speed manual?

If you have a THM 350 auto and you are not going to beat the hell out of it, your existing trans might be okay. Otherwise, consider a THM 400, especially if you are seriously building up the 455.

[Misfire_455]

I've got the three speed auto THM350. I do plan to beat on it as I am building up the 455. Do you know what I can get a THM400 out of?

[MrPbody]

Any non-Chevy GM A or F body from '67 through '74 with a will have the "short tail" TH400 (Pontiac calls it "M40"). As long as the trans will bolt up to the engine, and has the short tail, it will fit. You will need the TH400 crossmember for the '67-'69 Firebird. Those are readily available at Performance Years or Ames Performance. And yes, the little TH350 isn't the better choice for the bigger engine. For future reference, most parts (chassis and engine related) that fit the 1st gen Firebird fit the Ventura chassis.

FWIW, Pontiac did not make "biog block" or "small block" engines. If it isn't one of the "bastard" 265/301 short deck blocks, it's a "Pontiac". There are "large journal" and "small journal" blocks. The 421/428/455 uses a 3.25" main journal, where the 400-smaller use a 3" main. But deck height, bore centers, cam-to-crank centers are all the same, '55 through '79, 287 CID to 455....

If you would like more info on making the Poncho nasty, get Jim Hand's book "How to Build Max-performance Pontiac V8s" by SA Designs. This is a very current study of the old Injun and has a vast amount of information on building 10 and 11 second street motors. Chevy guys HATE Chapter 1! (the history of Pontiac V8s in racing)

Jim