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Old 05-23-2005, 01:36 PM   #1
mountainexplorer
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Casting #s on flywheels?

I managed to mix up all my flywheels.

I have a total of 5 manual flywheels. 2 are for SB400's. 3 are for 454's. I have a use for all of them, but seem to be having issues telling them apart now.

Three of the flywheels have the casting #3973457N

One has the #10101171 N

And the last one is #3986394

If anyone can decipher any of these, please let me know what's supposed to be what. Thanks.

-------------------------------------------------------------------
Don't read the following unless you want to be more confused-
Of the three 3973457N flywheels, one has a 454 crank inprinted shape on it, and two have small block imprints. One of these came off a 350 motor but was a factory 454 flywheel. The other had to have been off one of the SB400's, and the other must be a 454 one for sure.

All flywheels have the same balance weight on them (unlike automatic flexplates which I can visually see the balance weight difference).

Each flywheel has different amounts of counter drilling on the opposing sides of the balance weight. No drilling pattern is the same.

I have run each flywheel and know that none of them has been drilled to be zero balanced.

I guess I should have made sure I labelled and separated them before I stacked them all in the same pile.
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Old 05-23-2005, 01:46 PM   #2
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If no one can help you here, might try gmpartsdirect.com (email a question) to see what part #3986394 fits. That is likely the part number too (which is not always the case) since it comes up as a flywheel, so I would suspect they or a dealer can cross reference the part number to an application.

That was the only one of the three you posted that came up in my searches there.

Ha! Go figure
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Old 05-23-2005, 01:56 PM
Posted in reply to dyeager535's post starting "If no one can help you here, might try..."
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What's weird is that two of the 3 I have are 454 ones, and one is a SB400. I wonder if they all use the same casting flywheel, but just adjust for the SB400 by drilling them a bit different.

In any case, I still have two flywheels that I can't figure out which is which... 400 or 454.
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Old 05-23-2005, 02:19 PM   #4
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It looks like the:
3973457N is 454
This is a casting number, GM Number for it is: 3986391

10101171N is 454
this is a casting number as well. GM number for it is unlisted. That sometimes can mean the GM part number is the same, sometimes not.

3986394 is SB400 externally balanced. That is a GM Part number.

From those numbers, the only one that should have come on a 400 from the factory is the 3986394 one.
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Old 05-23-2005, 02:22 PM
Posted in reply to 73k5blazer's post starting "It looks like the: 3973457N is 454 ..."
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Quote:
Originally Posted by 73k5blazer
It looks like the:
3973457N is 454
This is a casting number, GM Number for it is: 3986391

10101171N is 454
this is a casting number as well. GM number for it is unlisted. That sometimes can mean the GM part number is the same, sometimes not.

3986394 is SB400 externally balanced. That is a GM Part number.

From those numbers, the only one that should have come on a 400 from the factory is the 3986394 one.
ditto on the 400 flywheel (3986394)my books for smallblocks shows that one!
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Old 05-23-2005, 02:47 PM   #6
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Thanks guys.

With that info, I can mark the 3986394 flywheel as a 400 and set it aside.

Now, I still have one of the two 3973457N flywheels to figure out. I bought one of the flywheels as a new one from a wrecking yard for the SB400. I wonder if they just take a GM 454 flywheel and drill it to be balanced for a 400.
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