How can I tell if I should replace my 401 Harmonic Balancer?

[rang-a-stang]

Still spec'ing my rebuild for this summer.

Is there a way to determine if my Harmonic Balancer is good/bad before I remove it? I searched my Service manual and the only instances of "Harmonic" or "balancer" relates to tire balancers. When I search the forums, I see hits on how the 401 balancer is different and how to pick a new one, but nothing on how to determine is one is any good.

Also, I plan to have my rotating assembly dynamically balanced. Does that impact the harmonic balancer?

[Ristow]

is the rubber squeezing out of it anywhere? also verify the TDC mark on it really tdc,if its off the outer ring has slipped.

[rang-a-stang]

I don't think so? (rubber bulging) I haven't had a good look at it. I have timed it and it runs well so I assume the timing marks are accurate. When the rain stops, I'll lay underneath and take a good hard look at it and see how it looks.

I guess I'll earmark a budget item for a "new" balancer and check for slippage once the heads are off.

[Ristow]

I have timed it and it runs well so I assume the timing marks are accurate.

that means very little.

[Ristow]

also,new ones need to be checked. the new one i bought for my 401 was 5 degrees off on the tdc mark.

[rang-a-stang]

that means very little.

HAHAH!!! I know! but off the top of my head, that's all I have. I will definitely check it! I'll do a quick check with a dowel through the spark plug hole sometime in the next couple weeks. Then when I do my tear down, I'll use a dial indicator to verify for sure.

[rang-a-stang]

also,new ones need to be checked. the new one i bought for my 401 was 5 degrees off on the tdc mark.

Rgr, saw that in another post where someone was asking about a cheapie balancer. I will verify mine and if I have to replace it, I will verify the new one, too.

[rang-a-stang]

Just found these guys:
Damper Doctor
Maybe I'll send my stocker to them for a rebuild if mine is toast. Anyone have any experience or heard anything about them?

[68glad]

I used them when i rebuilt my 401. I did not get my same balancer back. I took pics of it before sending and the new one had a different number on it. Prob a different part # for a different yr 401..idk. Didn't matter as rotating assembly got balanced anyways. If memory serves me it was 4 deg off. Used timing tape.(Summit tape highly recommended. super sticky. another brand flew off). Fast shipping & easy to deal with otherwise.

[rang-a-stang]

Great feedback 68glad! Thanks for the response. They wrote back to me today. Said:

Cost to rebuild is $136.13. We do not currently have this model for exchange. Turn around can take up to a week but are usually turned around in 2-3 days...

Hopefully I don't need a rebuilt Damper because my build budget is already too high but if I do, this seems to be the most cost effective way of doing it.

[FSJunkie]

I trust an original balancer in good condition more than I trust a new balancer, especially since these are externally balanced engines.

[Kaiserjeeps]

As previously mentioned, look for bulging rubber and also look for small cracks in the rubber. If it looks good with none of the above, and a light press with a blunt non sharp edge like a flat screw driver reveals a very firm rubber with a ever so slight bit of flex, you are good to go. With it's age though, it would probably be a good thing to freshen up if you can do it.