Today I am converting a 69 Cutlass S 350 engine/350Tranny to a 455 engine and BOP TH400 tranny. in measuring both tranny's are the same length so the drive shaft length should not be an issue. The issue is the TH400 has a larger gear so that my current yoke on the drive shaft is to small. I called the local O'Railly's and they are lost. I need some info on what would be the best way of getting this resolved.

 

I've always heard you'd have to shorten the driveshaft...

You'll have to snag the output yoke from a junkyard. The yoke isn't BOP specific, though. Any TH-400 will do.

C.J.

 

I also have another question. This is the bolts from Flywheel to Torque. On the 350/350 combo it had bolts that threaded directly to the torque. I see this is not the case. I take it that you have to use bolt/nut combo's to put the 2 together? If I am right then are these special bolts to handle the torque

 

That doesn't seem right to me. The flywheel bolts directly onto the torque converter on my Delta with a 455/400 combo.

 

Sounds like you have a aftermarket convertor. I would use grade 8 bolts and self locking nuts. Be sure to use small block OLDS motor mounts to the 455. The T-400 IS 4" longer, you will have to shorten the drive shaft.

Gene

 

Gene,

I just know what I've heard on ROP and elsewhere about the conversion...I thought 350 motor mounts were shorter and you were supposed to use 455 mounts...

C.J.

 

My experieces has been if your keeping the metal engine perches from the 350 then use 350 rubber mounts. If you change to the 455 metal perches then use the 455 rubber mounts. The bottom of the engines are the same so they both fit, but where the difference comes in is the exhaust manifolds. I mixed the perch/rubber mounts on a car with headers and the headers wouldn't fit. I had used this engine with these headers in a different car and they fit fine, so it took me a while to figure out what I did wrong! I've made the swap from TH350 to TH400 several times and always had to change the driveline to a shorter one. Check your trannies again to see what they are. They should have both been short tailshaft versions for the A-body car, but if someone put a long tailshaft TH350 in that might make them closer in length, I don't know, I've never compared the TH350 long to the TH400 short tailshafts.

 

Show me a little smarter today!

Check this out on transmission lengths:
http://www.tciauto.com/Products/TechInfo/trans_dims.asp

C.J.

 

Cool Link C.J. I copied that to my hard drive for future reference!

 

There's an awful lot of good stuff on that site!

C.J.