Can they be swapped? Or is the 440 flywheel externally balanced.

Depends on the application. Internally balanced flywheels can be interchanged as long as they are the same tooth count. Some engines are externally balanced and those most likely will not interchange.

383's were internally balanced, 440's with a steel crank were internally balanced so those flywheels will interchange; Now, cast crank 440's were externally balanced so those won't interchange with a 383.

Some '70-'71 383's were externally balanced and so were some steel crank 440's with heavy rods.

You're probably right John but I've never seen a 383 with a cast crank, even the 2 bbl. engines I've had were steel cranks and internally balanced.

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In addition to the balance weren't the pressure plate sizes often different?
10.5 vs 10.95/11 inch.

it's 10.5/10.95" vs 11" First two use the smaller sized flywheel, latter uses the bigger flywheel.

There are a lot of different flywheels, maybe six or more? between those two engines. Small clutch, big clutch, internal balance vs. external balance and then the 440+6 type of flywheel which is another variation of the external balance.

If you have a 130 tooth, internal balance flywheel you should be able to swap it between multiple Mopar engines including SB, B and RB. But only if the rest of the assembly is compatible. (bellhousing, clutch, rotating assembly balance, starter, etc.)

What is your 440 , what is your 383 ??

The flywheel and bellhousing are from a 70 383 from a challanger r/t. The 440 is from a 1978 motorhome. I wanted to install the 440 on an engine test stand and run it. The flywheel and bellhousing are needed to start it.

That motor, stock, is externally balanced, look at your flywheel to see if it was internally balanced or externally balance. if it has a bunch of small holes drilled or several large holes drill in it it might be external balanced

The bellhousing and flywheel will bolt on, but you will need an external balance flywheel for that year 440.

Figures,
Well thanks for the info guys. At least I will be able to mock up my test stand while searching for a flywheel.

No need to search. 440 source has a new billet flywheel, 130 tooth, and an add on weight for cast crank applications. Touch base with them to verify 440 cast crank. Under $250.

440 Source has a balance weight that converts a flywheel from neutral balance to external cast crank balance for the rock bottom price of $25.00

Part # 200-1168

Thank you, I will check it out.

I have two 71 383's with cast cranks, but everything I have read is that they were for automatic transmissions only...

The 1971 two barrel 383 motors got those cast cranks is what use to be said at the oild drag race seminar that Mopar put on before 1980