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After pulling the clutch and flywheel from the 228 in my 52 GMC 3/4 ton, I noticed that there are very fine, short cracks in the clutch disk contact surface on the flywheel. They APPEAR to only be in the surface of the flywheel. Now, to be honest with you, this makes me just a little nervous about putting this flywheel back in. I'm assuming that the cracks are a result of the flywheel being overheated a million times in the last 50 years? :confused:
Is this normal for these old flywheels and is it considered standard practice to continue using them? If it had come out of my GMC Caballero with the 396, I would be thanking my guardian angel that it didn't explode and that I'm still alive!

I think your instincts are right - the usual rule is to not run a flywheel with cracks. In the entire history of everything, no crack has gotten spontaneously smaller. 8-) They do get bigger.

I think you should get a new flywheel.

Cheers!
George

Take it to a clutch shop & see if they recommend replacement or resurfacing. GMC flywheels are pretty stout castings, not prone to cracking and usually outlast the vehicle.

Sounds like "heat checks" to me. Have it resurfaced, then see how bad they are. If the flywheel doesn't "clean up", by all means; replace it.
The flywheel shouldn't blow-up unless you like to rev up your engine and side-step the clutch at stop lights. GMC engine are relatively low speed engines, with stock redline about 4000-4500 rpm. I know I never ran mine that high; but it did see the 3k's........
Take it to at least two different shops before you throw it out; it's always good to get a second opinion.

Nearly every used flywheel I have had the opportunity to meet has had some heat checked surface on it. Only two were not able to be resurfaced at the machine shop.
Have it looked at by the machinist before tossing it out

Thanks to everyone for the advice concerning my flywheel. I dropped it off at the machine shop Monday morning and by lunch time it was ready. All of the "heat checks" came out of it and it is ready to go back in.
Fortunately, I tried and got over the high-rev, side stepping clutch routine back when I was about 19. At that time my Caballero had a 350 with a Muncie M21 4spd. I brought the engine up to around 3000 rpm and side stepped the clutch. I was only about a mile from home. This was a good thing, as it was a short walk home. $3oo later I had a fresh rebuilt transmission back in. Quick lesson learned, as that was the first and only time I tried that little stunt! :rolleyes:
Thanks again everyone!

Thank you for the feed-back and great news about the flywheel