In mid 72 the 340 got a cast crank, correct? What about 4-spd cars? Did they get a cast or forged crank? Late 72-73.

Only 73's had cast cranks. All 72's should have been forged.

They went to the cast crank in Apr of '72...

Only way to know for certain is to look at the damper on the engine...Cast crank has a different damper.

http://www.hamtramck-historical.com/images/TSBs/1972/09-07-72C%20page1.jpg

Part numbers are cast into the crank to ID.Is it out of the engine or pan off to inspect?

My 73 Challenger is a 4 speed, cast crank.
Doug

This pic was floating around a while back...
It shows the difference...
I Think it says "for use with 340 cast crank only" stamped on the front...

Ok thanks.
Have a friends 70 Cuda with a 340 that he took out of a 68 Barracuda but is a 71 casting and a 72 vin. It has a steel crank damper. Don't really know much about the motor but it has a really bad vibration. Seems to be RPM related. Have not pulled the pan but the crank is drilled for a pilot bushing.

I have a '72 model year 340 with a 9/30/71 casting date with a cast crank.

Before you go chasing problems, I purchased a vehicle from an owner who had an ASE shop/mechanic(s) tell him the engine that was swapped into his vehicle had damper/and or converter balance problems because the components had been combined between 2 motors by another shop,...I spent all of 5 minutes to discover that the plug wires on 2 cylinders were crossed over, sure felt like a vibration/RPM problem at the time, so eliminate the obvious before tearing into the motor

Mike

He has had this 340 in the car for a few years now and we have eliminated most everything else including the tranny.

Ok that helps. Thanks. He might have a cast crank with a forged balancer. As stated before 340 4-spd could have a cast crank.
Looks like we need to pull the pan to be sure.

You may be able to use an inspection camera up through the oil drain plug. The cast crank looks fairly different. I think the only challenge might be keeping the camera lens clean for long enough to get a good look.

Correction: windage tray may block the view.

The cast crank damper is easy to tell because is says right on it "use with cast crank only". I would pull the pan to be sure of what you have. The parting line on the crank will show you what type you have.
Another thing to consider is the flex plate will be 0 balanced for forged crank and weighted with cast crank. I made this mistake 25 years ago when I installed a zero balanced B&M solid flexplate on my cast crank 340. B&M does make the correct flexplate for cast crank 340....although I dont think it was available back then.

We swapped out the 727 for a 518 and we removed the 360 balance weight from the convertor.

Been playing this game for a while myself 72 340. Has cast crank with "for cast crank only" on balancer. Didn't believe it so put on known forged crank balancer. No difference in engine vibration. I believe that all 72 models after april have cast crank

Keep in mind that the 340 had the smallest external weight of any Mopar. If both the balancer and converter/flywheel are correct, replacing the balancer by itself might not make a noticeable difference.

He might have a cast crank with a forged balancer.

Or the other way around, ive a cheater motor I used a steel crank on and had it balanced with a cast balancer mentioned above that the cast 340s use so by looks it was a low performance 73 340 but it wasnt.

The 340 cast unit with its odd shape is semi hard to find I think.

Mine looked stock with a little bit of weight removed...

PM me if someone wants this crank and balancer, its got a bit more stroke the oem too.

The motor has a forged crank balancer but don't know which crank it has.
He is gone working for about a month so we'll see what he wants to do when he gets back.
May need that cast balancer.
Thanks