400 engine: Mix/Match flywheel and crank

[lumbee]

Hey all, getting close to running my 400 after a fresh rebuild and I have a question. Also, I fully acknowledge I should have thought more about this before this point, but here it goes.

I have 1972 Roadrunner (4 speed manual) and the numbers matching 400 block came with the car; the block only. I was able to purchase a good used 1976 400 engine and I have swapped all of the parts off of the donor engine into the numbers matching block, including the crank which also had the external harmonic balancer. I was told the donor engine came out of a Chrysler New Yorker so I'm guessing it was most likely an automatic transmission; though I'm not sure that matters. I have [what I believe to be] the original flywheel from the '72 RR along with the bell housing and manual transmission that I am planning to reinstall in the car.

Here is my question, can I use this flywheel? I'm concerned about it being balanced or neutral; I'm thinking its neutral but what are the implications either way? I really do not want to tear this engine back apart to balance it, but you all tell me what you think please.

 

[pnora]

If you have a cast external balance crankshaft you will have to use an external balanced flywheel and damper. Its that simple.

 

[RemCharger]

And is the crank drilled out.

 

[lumbee]

If you have a cast external balance crankshaft you will have to use an external balanced flywheel and damper. Its that simple.

OK, I guess my question is can I just buy an externally balanced flywheel and install it and go, or does it need to be balanced along with the crank at a machine shop?

 

[bigbluedodge]

I think they're both cast cranks so the flywheel should be correctly balanced. I don't know much about manual shift stuff though......except that the crank must be drilled for a pilot shaft.

 

[pnora]

OK, I guess my question is can I just buy an externally balanced flywheel and install it and go, or does it need to be balanced along with the crank at a machine shop?

You could buy one. What do you have now? Post a picture of it both sides.

 

[lumbee]

OK, I'll get a picutre of the backside, but can you tell from this if its neutral or externally balanced?

 

[pnora]

OK, I'll get a picutre of the backside, but can you tell from this if its neutral or externally balanced?View attachment 1889801

No. Your crank wont allow the input shaft to go in to the correct depth. You either need to have the crank drilled or modify the input shaft and use a special pilot bearing.

 

[origcharger]

I would be concerned that the early (72) manual trans 400 may have originally had a 383 forged crankshaft and was internally balanced. Since you don’t have original crank or damper and don’t want to tear it down again, you probably should have machine shop check it out.

 

[pnora]

I would be concerned that the early (72) manual trans 400 may have originally had a 383 forged crankshaft and was internally balanced. Since you don’t have original crank or damper and don’t want to tear it down again, you probably should have machine shop check it out.

He has newer external balanced internals. If he shows the other side of his flywheel that will tell the story.