TH 400 to pre-'72 engine

tarior

Can I just have my local friendly machinist open up the end of the crank to accept the snout on the TH400 converter, or does it also require a spacer to set it far enough into the pump?

tarior

Nobody knows??

AMX69PHATTY

The crank modification info for fitting a TorqFlite to an early pre-1972 crank is in the Performance American Style book that's available, but am not aware of a source specifically for the Turbo 400 interface. Would it stand to reason that the TorqFlite mod would also work maybe for a Turbo 400 since there is not a 3rd kind of AMC Crank ??? I'm not sure not being a Jeeper, but didn't Jeeps with AMC 304's, 360's, & 401's come with both TorqFlites and/or Turbo 400's in different years, but the aft end of the cranks are the same ? hmmm interesting question.....
Here's the mod for using a TorqFlite on an early Borg Warner style Crank.
Maybe, can you measure the Pilot on the 400 Converter, Diameter and Hieght, and I'll measure one on a 727.......
where's my calipers ........
ok crank pilot .900 tall x 1.817 dia. on a 727 Converter for an AMC.
Pilot is dirty, diameter must be 1.810 to fit hole shown on below sketch

tufcj

I believe all the 72-up cranks were machined for the 727 converter. From 76?-79, when they used TH400s in Jeeps, a small spacer ring was installed in the back of the crank because the TH400 converter is slightly smaller. You could use the ring above, and just have the ID machined to fit the TH400 converter.

There might be more info at www.amcforums.com

Bob
tufcj

tarior

I'm working with a '70 360 specifically, I don't see why the end of the crank couldn't just be opened up enough to accept the TH400 converter snout. I will never use a 727, so there is no need to make it that big. My main question is whether there is enough length on the snout to engage the end of the crank sufficiently, and if so, will the the torque converter be all of the way into the pump?

AMX69PHATTY

Is the 360 motor apart ? You could just buy a late model '71 and up 304/360 crank kit already turned and polished with rod and main bearings for about $150 and the problem would be solved. The '71 and up 360 crank is the same as the '70 unit, it just has the proper aft flange for your tranny, except it would require the ring that tufcj mentioned. Only snag would be if you've already had your rotating assembly balanced, that would have to be redone using the new '71 & up crank. Would that do the trick ? Cause per the modification sketch there's a .21 inch difference between the two, the '71 & up being longer, and I dont know if I'd like having .21 inch less engagement between the converter drive lugs and the pump gear. The nothches in my 727 converter are .68 inch deep. Besides the final location of the converter in the stack up is determined by how it mates to the flexplate, and the flexplates mounting to the crank flange, so the 400 converter forward snout may end up not being properly engaged in the hole in the end of the '70 crank without the adapter which effectively lengthens the crank by .21 inch. Is there some reason you couldn't just get at late model crank kit ? That sounds like the way to go.

tarior

This motor is assembled and ready to go, I was planning on using a manual trans when I put it together, but I had to put that off until next year. I have 3 360 core motors floating around, but I think I will just slap in an old 401 I have laying around and use it with the TH400. Thanks for the answers.

jeepsr4ever

Going with the 401 isnt all bad :wink:

tarior

I was just hoping for some semblance of fuel economy. :?:

jeepsr4ever

tarior wrote
I was just hoping for some semblance of fuel economy. :?:

You must seek elsewhere my son' For all their wisdom the AMC legends put all forth the effort but spared us from the perils of fuel economy.
:king: