Recently purchased a '69 convertible with a stock OHC 6 (non sprint) and the ST300 (2 speed) trans. I'd like to move to a V8 and turbo trans.
I have a lead on '72 400 motor out of a Catalina along with it's TH400 with the long tail shaft. I'm wondering what modifications I would need to make in order to use this combination in the car?
From the factory, did Firebirds with TH400's use the long or short tail shaft?
Should I obtain the drive shaft from the Catalina for possible use? (i assume the spline count is different coming out of the trans between a ST300 and a TH400)
If I could find a TH350 trans, would that be a more direct bolt in?
You need a short shaft TH400 then the stock TH400 crossmember will work as will a stock firebird TH400 driveshaft. You will have an easier time going with stock setups, be it TH350 or short tail TH400. Then just scrounge the parts. A TH350 will use the same cross member as the ST300 and should be the same drive shaft.
So for a quick turnaround it looks like a TH350 is the way to go as I'm 2/3's there (cross memeber and drive shaft). Does a TH350 have a TV cable or any electrical hookup I'll need to do?
Also, do you know if a 200-4r would bolt up directly in place of my ST300? (in other words, is a 200-4r the same length as a TH350?) I realize I'll likely need a different cross member. Having overdrive would be nice for cruising down the hyw.
The 200-4R has both the Chevy and BOP bolt pattern, same spline count, and is the same overall length as the ST300. But the trans mounting pad is not in the same position. Good news is, the 200-4R trans mount is in the same position as the short tail TH400. In other words, switch to a TH400 cross-member and it's a bolt in.
You'll need a bracket to hook up the TV cable to the carb linkage, and control kit for the convertor lock-up. (These should be available through B&M and others). And finally, a shifter conversion kit from Shiftworks, so you can control all four gears manually. The 200-4R has a much deeper first gear, so it will improve acceleration (and even city mpg as you won't need as much throttle), while the overdrive improves fuel economy.
Heck even if the V8 doesn't pan out, the improvements in off-line acceleration and fuel economy would still be worth the swap.
awhile back when rebuilding my engine, was looking into transmission, thought turbo 400, picked one up that needs rebuilt. starting researching, original on mine was the t-200. unless your pushing lots of HP, dont go with a t-400, uses to much hp. go with a t-350. I got one that was in a 76 trans-am. works great.. so the 400 is still sitting in the barn. collecting dust. but i am holding onto the t-200. original equipment..
