Dave Powell

For my '67 roadster I bought a Goodwrench 350 (#12355345) years ago and the flywheel with it from the local Chevy dealer. Now that I've removed the side pipes I have a very noticeable engine vibration especially around 3500 rpm (which was probably masked by the noise of the now-gone pipes).

The invoice shows flywheel #366860 although another thread says that's for the 10.4" clutch, while mine is 11". The engine sheet specs a 10105832 flywheel for 11".

This engine has a one-piece rear seal, thus is externally balanced as I have read (and as is mentioned in the engine sheet).

The question: does anyone know if the 366860 flywheel is or is not an external-balance unit? On line I find many references to the flywheel but no certainty that it ISN'T an external. Before I buy (another) flywheel I'd like to be sure that's the problem.

Dave Powell

66BlkBB

Check this forum out. According to the members there it is an externally balanced unit.


http://forum.ih8mud.com/40-55-series...-flywheel.html


PS.
My error. Thought you were still looking at the 10105832. The one you are currently looking at appears to be made in China. Look at the listing in the other site, they list a CenterForce replacement unit I believe. NAPA has a direct replacement unit also.

Dave Powell

Thanks for the reply, but I'd already checked that site, and I find nothing there or in the linked site about this flywheel 366860, so I still need to know if it is an external balance unit.

I saw the site about Chinese pieces, but I bought this one in 1994 from GM.

JohnZ

Do you have a photo of the engine side of the flywheel? That will show if it's neutral-balanced or counterbalanced.

DZAUTO

Starting with the 1986 350 engines, which is when the change to a one piece rear main seal occured, all flywheels were EXternal balance (or UNbalanced if you prefer). Furthermore, 55-85 and 86-later flywheels ARE NOT interchangeable!!! BOTH the center hole and the bolt pattern for the crankshaft are totally different.

Now, for BB engines, ONLY the 454 used an UNbalanced flywheel. Then in 91, when the BBs went to the piece rear main seal, they still used an UNbalanced flywheel.

Dave Powell

I don't have a photo of the flywheel, which I installed in 1994.

I realize that the engine requires an externally balanced flywheel. What I need to know is whether the 366860 flywheel IS or ISN'T externally balanced. It was used even with V-6 engines and I suspect it is not. I just don't want to invest in a new flywheel and all the labor only to find that the flywheel the dealer sold me with the engine was a correct part.

Scott Marzahl

I did some searching online and it looks like this is a 82-85 F body flywheel but still looking around.

buns

The 366860 flywheel would not bolt up to your 1 piece rear main seal crankshaft.

Dave Powell

I'm going by the invoice from when I bought the engine, and it shows 366860. I saw one thread that said that flywheel was for the smaller clutch, but what I have is the 11" clutch.

It would be nice to be able to see a number on it, but a flywheel just isn't cooperative that way.

It sounds like I'm going to have to bite the bullet and order the correct flywheel, 10105832. I went to the dealer today and he said that one is superceded now, too. At least there is still an externally balanced piece available.

Scott Marzahl

Summit has good prices on gmpp flywheels

Dave Powell

I will check Summit. Thanks!

6T7L71CPE

I would think you could take off your starter, rotate the engine manually and look for the extended chunk of casting that is the external balancing weight. Look at pictures online for examples. Not all catalogs have actual products shown.

Dave Powell

I had the starter off recently and saw no weight. I also don't remember a weight from when I installed it, just an ordinary flywheel. I take it that it should be near the edge? If so that answers my concerns.

Summit has a good price on the current externally balanced flywheel, so I think I'll buy one from them.

ssgnco

Yes, this is correct. And these years had a 2-piece rear main crankshaft. This flywheel will not in fact bolt up to your one-piece rear main crank. See:

http://www.gmpartsdirect.com/perform...CATID=913.html

So, either you don't really have a 1-piece rear main or you do not have this flywheel. This flywheel is discontinued. Pictures I could find of this flywheel (which you probably do not have) do not show the balance weight casting. Of note, the "balancing weight" is cast into the flywheel on the stock flywheels and is not all that obvious unless you know what it looks like.

ssgnco

Oh, and BTW, I think you have to use the lightweight flywheel
14088646


It's the only GMPP one that is 153 teeth, 11" clutch and 1-piece rear main (3-inch bolt pattern). There are lots of other aftermarket options out there though.

DZAUTO

An 11in clutch will NOT bolt up to a 153teeth flywheel. The bolt pattern for an 11in clutch is larger than the diameter of a 153teeth flywheel.
To use an 11in clutch, the larger 14in diameter, 168teeth flywheel is required.

For 55-85 SB engines (2-piece rear seal), there was never a FACTORY EXternal balance, 153teeth flywheel.
ALLLLLLLLLLLL of the FACTORY EXternal balance flywheels for a SB were the larger, 168teeth version.

VISUALLY, the EXternal balance SB400 flywheel and the EXternal balance 454 flywheel look the same (BOTH are the 14in, 168teeth version). The difference between them is the final balance (or UNbalance if you prefer).


Below is a comparrison of a 153teeth and a 168teeth flywheel.
AS CAN BE CLEARLY SEEN, THE BOLT PATTERN FOR A 10.4 CLUTCH ON THE 153TEETH FLYWHEEL IS VERY CLOSE TO THE OUTER DIAMETER OF THE FLYWHEEL. THUS, THE LARGER 11in CLUTCH COULD NOT POSSIBLY BE BOLTED TO A 153TEETH FLYWHEEL!



Below is a comparrison of a neutral balance 168teeth flywheel (left) and an EXternal balance flywheel (right) such as would be used on a SB400 or a 454.



The flywheels for the 86-later SB and 91-later BB are TOTALLY different in regard to center hole, crank bolt pattern and weight. They are UNbalanced (or EXternal balance if you prefer), but the added weight is totally different from the added weight of earlier SB400 and 454 flywheels.

If absolutely necessary, I can post a picture of the later style flywheel/holes/weight, BUT in order to take pictures, I have to move the 56 and the T-bucket out in the snow to gain access to the cabinet where my stash of flywheels is located.

ssgnco

An 11in clutch will NOT bolt up to a 153teeth flywheel. The bolt pattern for an 11in clutch is larger than the diameter of a 153teeth flywheel.

Interesting. I can definitely see what you are saying. I wonder why the GMPP website says this flywheel will work with the 11" clutch? Must be a mistake in the website?

As a side note, you can easily create a problem for yourself if you're not careful. I built a 383 on a late 1-piece seal block using an internally balanced rotating assembly. Took me a bit of work to find a post '86 flywheel without the balancing weight -- it was available though...found an aftermarket with a removable weight.