Harmonic Balancer Hub Washer/Gasket... help???

Some kind of shim, looks like. Rubber to give the damper a little axial play for some reason GM must have thought was important.

Not a seal, since there's no signs of wear or any fluid leak-by.

Compare old to new to see if there's a dimensional difference in the height of this mounting flange. If there isn't a delta, re-use the OEM part.

It’s a high friction washer. It keeps the balancer from rotating any. Brian Tooley explained it to me at an open house. They used to sell them. They’re supposed to be one time use. I replaced mine on my new motor with my ATI balancer.

GM #12578073. It might come without the rubber but it works the same.

MeanMike said:

It’s a high friction washer. It keeps the balancer from rotating any. Brian Tooley explained it to me at an open house. They used to sell them. They’re supposed to be one time use. I replaced mine on my new motor with my ATI balancer.

GM #12578073. It might come without the rubber but it works the same.

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Thanks for the replies (and the PN Mike) ! I know it wasn't a seal even though I used that word .

When I put the ATI damper on my engine I didn't install one, hopefully it won't impact the belt alignment. I had them add a second keyway in my Callies crank so I'm not sure I could have installed one anyway without modifying it. Also ATI mentions a groove in the hub for it which I didn't see in the ATI hub I have My hub was just tapered at the end, but if I'm seeing your hub in the background of the first pic it looks like it's made for one.

How thick is the washer?

From ATI

"Depending on the year of your engine / vehicle you may notice a thin “friction” washer behind the damper hub in front of the first oil pump gear. This washer should be left in place and will not hurt anything if you are or are not pinning or keying your crankshaft. If your year does not have this washer and you would like to add one, there must be a machined “lip” provision on the back of the hub to do so."

SaskV said:

The flat metal washer part is about .005. As the instructions call it a "friction" washer below.

Yep, there it is, #2 on "installing the hub on the crank"... I should have "read" the instructions I guess... sheesh! 🤦‍♂️

Thanks, I appreciate the replies!

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Thanks for the response. I just looked at the single keyway hub that came with the ATI balancer and it does have the groove like yours. I had to buy the hub that had 2 keyways to match up to the crankshaft. I could swear that it was just tapered on the end but in the ATI pics it shows the groove in it also but I really don't want to pull the balancer just to check it. Since the replacement washer doesn't seem to have the rubber, it doesn't look like you'd need the groove to run it. Either way I would have had to cut the washer for the second keyway. I don't think .005 will impact the alignment enough to matter but time will tell.

Has anyone ran an ATI balancer without the washer and if so did you have any problems?

rpol78 said:

Thanks for the response. I just looked at the single keyway hub that came with the ATI balancer and it does have the groove like yours. I had to buy the hub that had 2 keyways to match up to the crankshaft. I could swear that it was just tapered on the end but in the ATI pics it shows the groove in it also but I really don't want to pull the balancer just to check it. Since the replacement washer doesn't seem to have the rubber, it doesn't look like you'd need the groove to run it. Either way I would have had to cut the washer for the second keyway. I don't think .005 will impact the alignment enough to matter but time will tell.

Has anyone ran an ATI balancer without the washer and if so did you have any problems?

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You'll be fine without the washer. The alignment of your keys probably isn't absolutely perfect and your balancer likely can't move at all. The belt alignment is a non issue.

The balancer is meant to absorb rotational vibration. For the really high frequency stuff, the balancer can move the key. This washer is to prevent that. Being as that we are all running these with a big supercharger and corresponding belt, that adds to the damping ability. Torsional damping on our motors isn't much of an issue.

Thanks Mike. I'm going to run the Kong 2650 so had the second keyway added.

Someone posted that the rubber was to seal the balancer so that oil wouldn't leak between it and the crankshaft. I wonder if there's any truth to that. I figured since it was so thin (i.e. .005) that it was to hold it in place on the balancer to prevent damage while installing it.

rpol78 said:

Thanks Mike. I'm going to run the Kong 2650 so had the second keyway added.

Someone posted that the rubber was to seal the balancer so that oil wouldn't leak between it and the crankshaft. I wonder if there's any truth to that. I figured since it was so thin (i.e. .005) that it was to hold it in place on the balancer to prevent damage while installing it.

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I don't think that's what the rubber does because it doesn't' completely go between the balancer and oil pump drive. I think it just holds the washer on the balancer for assembly.

I always put a little RTV under the head of the balancer bolt to prevent any oil from coming out of that area. My washer doesn't have the rubber and it's a GM part number.

After all of this I "carefully" installed the balancer the other night and all went well. Carefully in quotations because today... TODAY, I find the &%$#@ friction washer ON THE DAMN FLOOR in the corner by the front of the car. AYFKM??? Where's the largest face-palm emoji I can find! 🤦‍♂️ I MUST have knocked it off somehow without noticing before I slid the balancer on the front of the crank. OMFG, I can't believe it !

Do I remove the balancer (I really don't have the proper puller for the ATI balancer) or just call it good? 🤷‍♂️ (feeling dumb, but ready to accept it LOL)

I guess now you get to run through the jungle bare bottomed like me

If it were me, I'd be pulling it back off to put the washer on but I'm OCD like that. But I don't think it will cause any harm to leave it off, especially if it was the original (used) washer.

The ATI balancer comes off with a regular 3 bolt balancer puller that you can find at any auto parts store.

rpol78 said:

I guess now you get to run through the jungle bare bottomed like me

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🤣🤣

MeanMike said:

If it were me, I'd be pulling it back off to put the washer on but I'm OCD like that. But I don't think it will cause any harm to leave it off, especially if it was the original (used) washer.

The ATI balancer comes off with a regular 3 bolt balancer puller that you can find at any auto parts store.

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I am very much in the OCD crowd! Thanks Mike, I suspected it came off with a standard puller ! Stay tuned, I am very likely going to pull and replace!