Thread: turbo 350/ 400 swap

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i have a 71 four door nova and i put a 430 hp 350 in it and im also up grading the trans. I want to put a turbo 400 in it but the cross member is about a foot shy were the trans and the crossmember meet. shuld i just push the crossmember back or is there a kit?

Originally posted by super nova 71
i have a 71 four door nova and i put a 430 hp 350 in it and im also up grading the trans. I want to put a turbo 400 in it but the cross member is about a foot shy were the trans and the crossmember meet. shuld i just push the crossmember back or is there a kit?

you can do what ever you wont super nova but i think a good th350 is as good as a th400. and ive had both behind blown motors, but thats up to you. its been a while sense i changed one but i don't remember having to move the cross member over a few inches ether way. sounds like you've got the shortest th350 and the longest th400 to work with. go over to search and look it up. its a some threads over there that will tell you what to do.

Bolt the 400 to the motor, unbolt the cross member and slide it back and bolt the trans mount to it, then drill through the frame and cross member in the new location and bolt it in, two will probley hold it but I use four.
Now measure the drive shaft that will have to be cut to fit.

Just out of curiosity, what would happen if you bolted the shorter tailstock from the t-350 to the t400? Would it work? and if it did, couldnt he just use the factory driveshaft? I know GM had a lot of common parts among trannies

Don't believe it will bolt up, the mounts are in different places anyway ( see above pic ) and having a machine shop cut and balance it is no big deal, the one I had done last year was only $30.00 and was done the next day.

Originally posted by drg84
Just out of curiosity, what would happen if you bolted the shorter tailstock from the t-350 to the t400? Would it work? and if it did, couldnt he just use the factory driveshaft? I know GM had a lot of common parts among trannies

drg to make it work you would have to change the out put shaft and you cant do that. looks like to me he has the short 350, and the long 400 and i dont think thats gonna work ether, without a lot of extra work. he said he needed to move the cross member back a foot. im not sure you can move it back a foot.

thanks for all the imput but i was told that you couldent move the crossmember beacouse it was there in that spot for a reason?.

Originally posted by super nova 71
thanks for all the imput but i was told that you couldent move the crossmember beacouse it was there in that spot for a reason?.

Yeah, it's there to hold up the rear of the trans, moving it back and reattaching it won't hurt a thing.

Check your front subframe to see if you don't already have two sets of holes in it. Lots of GM cars from the mid-60s all the way to the late 70s have two mounting locations for the crossmember.
The one closer to the engine is to locate manual trannies, PowerGlides, and THM 350s. The one further to the rear is for the THM 400s. Some '68 and '69, and possibly even a few '70 Novas came from the factory with big blocks and 400 THMs. It's also possible to use a factory driveshaft from a big block/THM 400 Nova for your application; IF you can find one. It would save you some expensive fabrication work.

I agree with the other guy about using the THM 350. They are plenty tough enough to handle any smallblock Chevy with no more than a good (TransGo, B&M, etc.) shift kit added. And, a THM 350 weighs about 50 lbs. or so less that a THM 400, and that's equivalent to installing aluminum heads.

The only reason I could justify a 350 to 400 swap myself would be either because I switched to a nasty big block, or because I preferred the superior shift quality of a 400. Ain't nothin' shifts like a 400 Turbo in a Buick Electra; silky, but firm Man, and you gotta love that!.

Randy

Your subframe may be very similar to the one on my camaro. I had a 350 cross member and it wouldn't work with the 400, I found a 400 crossmember and it bolted right up, there ought to be one available for the Nova, it may even be the same as the camaro one. Forgot where I picked up the crossmember from but I think it was from a Chevy dealer parts counter. Been a long time since I looked at both crossmembers but I think one has the mounting bracket welded in front of the member and the other had the mounting bracket welded in back. The member is also bent for exhaust pipes to go underneath.

super nova 71, i've changed back and forth many times between the 350 to 400 and its done ever day, every thing everyboby is telling is good info.(excpt the one telling you, you cant) the only reason i said anything in the first place is, because you said it needed to move a foot, and that dont sound right, but a few inches either way is fine. ive built and raced both trans and personally dont see a lot of dif. in either, just depends what you wont. if you want to change trans. go for it. JMO