Cranky Pants...

[66stepside]

Err, I meant Crank parts! “Honest”.

What’s the difference, or big deal about early AMC 360 Cranks?

Exhibit A: older 70ish ‘cranky pant’:




Exhibit B: 72 and newer ‘cranky pant’:




Why do people avoid the older style cranks?


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[FLeetFox]

I think the main thing is you need to use a flywheel from the same era. The flywheels are not interchangeable between Gen II and Gen III AMC v8s. And the flywheels vary by displacement. And must be externally balanced. Others may have more to add.

Fleet Fox

[66stepside]

I think the main thing is you need to use a flywheel from the same era. The flywheels are not interchangeable between Gen II and Gen III AMC v8s. And the flywheels vary by displacement. And must be externally balanced. Others may have more to add.

Fleet Fox

That makes sense. Thanks.

I have a spare 360 block and everyone is asking what the back of the crank looks like. I’ve never had anyone ask before, but this block is out of a 72, so maybe that’s the reason people are now asking about the rear of the crank.


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[PossumJr]

From my understanding, AMC changed from the flat flange which was common to the Gen II cranks, to the stepped flange in 1972 coinciding with them changing over from Borg-Warner transmissions. Flexplates and flywheels are not interchangeable between the two (on top of the external balance issue for different displacements) which I would assume limits your transmission choices to the B-W units for direct swaps, but I think there's options for machining, adapters, and special (expensive) conversion flywheels/flexplates so you can use a Torqueflite or Hydramatic with a flat flange crank.

Not super familiar with all this so hopefully someone can correct me if I'm wrong anywhere.

[tgreese]

There were AMC 360s in the Wagoneer and J-trucks in 1971. I presume these have the flat flange. Jeep used the GM TH400 in all such equipped models and carried through until 1979, starting in 1965 with the AMC 327 and AMC 232. Jeep used the Borg-Warner transmission with the 230 OHC six, but never thereafter in civilian Jeeps, AFAIK (postals got the Borg-Warner, then the Torqueflite. I think the Chevy 153 postals got a Powerglide, but I'm not certain).

This AMC change from Borg-Warners to Torqueflite transmissions was in the passenger cars, and did not affect Jeep other than the crank shape changing the mechanics of attaching their choice of transmission to their engines.

Jeep used an adapter between the TH400 and their engines until 1974. It appears that there is a unique adapter for the 1971 304-360, while all 232s and the 1971 258 use the same adapter. However, all 304-360 that are adapted this way use the same flexplate, while the 6s are all the same 1971 or older. There is also a spacer that is unique to the '71 V8s, while the 6s don't change for '71. This is laid out in the parts book available at the Tom Collins site.

[FLeetFox]

A 72 model Jeep could easily be a left over 71 with a less desirable equipment package... Tim, the borg-warner explanation makes the most sense. SC/397 on the Mother Ship would have a more detailed answer.

Fleet Fox

[66stepside]

Thanks for the responses. Having more access to modern transmissions makes sense as to the reasoning as one potential engine buyer did mention he “would have to buy a new crank” if it were the older style.


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