Noise from crankshaft pulley?

[Rough75C20]

Hello all,

Discovered a rattling noise coming from my crankshaft pulley. I noticed this morning almost like a rattling noise coming from the belts. further investigation showed noise coming from the crankshaft pulley area. Cant identify the cause because the belts seem to be in good condition and the correct tightness. Any ideas? I couldn't figure out how to post the video here so there is a link to my tiktok page showing the video. Engine is a 1982 305.



Thank you

[Rough75C20]

https://www.tiktok.com/t/ZTkGYgH2u/


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[bd]

It looks like the elastomer ring is walking out from between the balancer outer ring and its hub.  The outer ring is probably slipping, so you will need to replace the balancer assembly and seal.  A still picture should make it more discernible.  Don't wait too long, or the ring might begin to rub and drag against the timing chain cover.  Good weekend project.

[Rough75C20]

Hello Bd,

Thank you I will try to get some pictures later today.

Thank you


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[Rough75C20]

Well I think you were right about the balancer I believe the noise was the rubbing on timing chain cover. I believe it’s the 6.75 inch diameter balancer. Do I need a new pulley as well? Also, where to get a new seal?

Thank you


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[bd]

Be sure to pick up a dampener for your specific year, model vehicle, and engine so that the timing marks are correct (assuming the engine is original).  The dampener and timing marks need to match.  Replace the front crank seal too (it may or may not come with the new dampener).  That pulley looks like someone beat on it with a large hammer.  The resulting dimples have narrowed the groove, squeezing the belt.  If you can find a proper replacement pulley, it would be prudent for the sake of belt life.  In the meantime, don't drive it.

[Rough75C20]

Thanks bd, I will be replacing everything.

Thank you


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[Rough75C20]

Why does my truck seem to have a different style crank pulley? It seems to have a serpentine style belt in the front and two v style slots is this normal?

Thank you


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[bd]

That isn't normal for a 1975 vintage truck.  Serpentine belts came on ca 1985 (?) and later vehicles to drive the alternator and water pump.  The one imaged below may work, but is machined from aluminum making it pricey: https://www.summitracing.com/parts/mch-4021-08/make/chevrolet.  In addition, a reviewer said it is smaller than the OEM pulley, although the manufacturer claims otherwise.  With a little leg work and Internet searches you might find other brands that are steel and less expensive.

[Rough75C20]

Hello all,

Trying to make sure I get the correct balancer. What is the important factor here? The overall dimensions are 6.75 inch diameter, 1.25 inch diameter center hole. The timing mark is between the 10 o clock and 11 o’clock position relative to the keyhole when looking from the front. It has a hollow back as well.
See pictures. Want to make sure I order the correct one there seem to be many options available. I’m looking at this one on rockauto part atp 102069.

Thank you


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[bd]

The original GM part number for your balancer is 458653.  Try to determine if there is a part number interchange list to ensure compatibility.  Otherwise, the ADP number you're eyeballing appears correct. 

FYI, bear in mind that the outer ring of the old balancer is no longer indexed to the hub and may have rotated in addition to slipping rearward.  So, don't rely on timing mark comparisons between the old and new balancers during the selection process.

While you have it apart, it looks like the water pump is seeping coolant out of the weep hole.  You should consider replacing it, too.

[Rough75C20]

Thanks for the info bd. I’ve also heard there are multiple water pump part numbers for these engines. I’m looking at an ac delco 252595. Is there a way to confirm this is the correct part number for the one on my truck?

Thank you


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[bd]

...I’m looking at an ac delco 252595. Is there a way to confirm this is the correct part number for the one on my truck?

That is the ACDelco p/n that comes up for a 1982 C20 w/305.

[Rough75C20]

Thank you bd. I’m sure I’ll have some more questions once I start putting everything back together.

Thank you


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