The Stovebolt Site Forums The Shop Area Engine Shop How to get a 6 bolt flywheel onto a 4 bolt crank

Hi, I'm trying to install a hydramatic transmission in my 53 GMC 3/4 ton with a 216 engine. After removing the flywheel I was left with a 4 bolt flange. Did hydramatics not go on 216s? everything else fits, intermediate bell housing,dowels. I havent changed the pilot bearing for a bushing yet but it doesnt look like a problem. should I be looking for a different engine or crank? If anyone has an insight please help me out. In the mean time I will continue to read.

I think you need a 1954/55 Chevrolet 235 engine or GMC 248 (6 Volt) to work or you need a 270 or 302 GMC engine (The 302's all came with the 6 bolt flywheel). GMC made a 6 hole flywheel for the 6 volt but they are hard to find, you will have to go to a 12 volt flywheel and starter.

What year hydra-matic do you have? Is it complete?

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There are several HM guys on board.

You would be better off staying with all GMC parts for this.

GMC torus cover(flywheel) is made special for GMC hydramatic.

It seems strange that you have a 216 in a 53 GMC. Is it a Canadian model? Or is that a replacement engine for the original 228/248/? that was in the truck with a Hydramatic? Please elaborate. As others have implied Hydramatics never came behind 216's.
I did read of a guy that managed to put a Powerglide behind a 216 once. So it might work with some machine work...
Good luck.

A 1953 USA GMC would have most likely come with a 228 (or, maybe a 248). 1953 was the first year for a Hydra-Matic in a GMC.

In 1954, the Chevrolet Hydra-Matic came with a 235.

I believe that 1939 216s used a four bold flange. Did not use six bold until 1940 or 41.

In this article Patrick writes that 41-62 Chevy crank flanges are all the same. http://www.patricksantiquecars.com/articles.html
So 40 and before must be different.

I'm not sure why he says 1940-62. 1940 and 41 were six bolt, but used 3/8" mounting bolts, and they also had a larger center hole in the flywheel.
1937-39 used four mounting bolts.

Yes I have a complete Hydramatic which I believe is a 1953. It is complete with a mid housing for the flywheel which I also have. It is compatible. Anyone have a cheap 235 or 248 in the
SF bayarea?

The break down for the engine number on the block shows that this engine should be a 228 made in Oakland in 53. I was assumming it was a 216 because of the flange. let me check again.

After rechecking the serial number it should be a 228.
152 22 C 4690
3/4ton with 125.25 wheel base, 228 engine, made in oakland, with no production year indicated.

The engine serial number for the GMC's starts with the size. Stamped on the flat boss behind the distributor: 228xxxxx

Sorry for taking so long Frank. I rechecked the engine number and it is a 228. So now I'm down to getting a 235 engine that is not so hard to find. Or getting a GM crank shaft with 6 holes on the flange. I think I'll go for the 235, it seems less risky.

Would you clarify what the Hydra-Matic is out of?
Chev and GMC six bolt crank pattern are different so your flywheel is specific.
I believe the four bolt pattern is the same for Chev & GMC.