flywheel collision (383?)

[Sparky]

I built my 383 a little over a year ago, and I have approximately 10,000 miles on it. I didn’t have any problems for the first 8000 or so. It slowly started making a noise which progressively got worse. The noise turned out to be the weight on the flywheel hitting the transmission dust cover. So I removed the dust cover and the problem went away. Just got a new truck (daily driver), so the Blazer has been sitting lately. Drove it the other day, and the noise came back only the dust cover isn’t on it. Has the exact same symptoms as last time. The noise only occurs under hard acceleration

The engine is a 383, so it is externally balanced, and has a large weight on the flywheel. I think it may be hitting the casting on the back of the engine where the last bearing for the cam shaft is (no visible scaring on the flywheel yet). Only problem is, I don’t know if I have any real problems other than a large weight. All I can think is that the thrust bearing in my engine is going out. The flywheel does not appear to be spinning out of round or anything funny like that. Oil pressure is still good. Any thoughts or similar problems?

Thanks

Ryan

 

[sled_dog]

must be bad thrust bearing in my mind. No other reason I can see it would happen under acceleration. Crankshaft is walking under load.

 

[84_Chevy_K10]

You don't have a flywheel. You have a flexplate. Yours is likely cracked.

 

[sled_dog]

didn't even read his info. Agree with Tim now that I realize you had an auto. Its more likely cracked flexplate than bad thrust.

 

[jp0863]

if it uses the same flexplate as a 350 (i dont know), i have one laying around thats in good shape. you can have it, just pay shipping.... i'm not too knowledgeable on gm engines, but if it'll work, its yours if you want it.

 

[Sparky]

yeah, i guess it is technicaly a flex plate. Flywheel emplies that its mass serves a purpose, but I hear them called flywheels on autos all the time.

Where do the normally crack? Where it bolts to the crank shaft, or where it bolts to the torque converter? Everything I can see looks good, but I cant see the crank shaft/ flex plate bolts.

If it is the flex plate, can a good machine shop match balance one for me? I had the rotating assembly balanced when I built my engine.

Anyone ever check crank shaft end play with it in the truck? I think it is possible that the weight on the flywheel is hitting even with an acceptable amount of end play. The weight on the flexplate is large enough that it sticks out past all of the teeth for the starter and all of the torque converter bolts. I remeber questioning it when I built the engine. Now that the engine is broken in, it may be just enough to cause the weight to hit. (at least that is what I hope since i dont feel like building another engine)

Thanks again

Ryan

 

[wasted wages]

[ QUOTE ]
Where do the normally crack?

[/ QUOTE ]
Mostly around the crank hub,,,was it a used flexplate???
A lot of times the stress risers caused by lock washers can cause crack to start arround the bolt holes and will spread.

For the cost of a flex plate I always toss a used one,,,

 

[84_Chevy_K10]

Yep, exactly what happened to me this year. If I had it to do all over again I'd never reuse a flexplate, such a pain in the ass when they go.

Don't worry about the balance just throw a new one on there. Your engine is still much better balanced than any factory one.