Harmonic Balancer

[tmbonnett]

Should I be concerned with the condition of the rubber on the harmonic balancer for 69 302? I’m rebuilding the engine and noticed that the rubber is brittle and cracking around the edge.

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[Master Chief]

Yes, replace it. I removed this from my 1969 engine and was able to separate it with very little hand pressure.

 

[Slowleak]

Replace it. It’s just a matter of time before it turns loose or starts to slip. When I put on a new one, I mark it so I can tell if it ever does slip...

 

[Lawndart]

Or send it off to DamperDudes to have it rebuilt.

 

[WILDHORSES]

I would always replace the balancer when building a motor. Here's a few examples of new ones.
https://www.wildhorses4x4.com/category/s?keyword=harmonic+balancer

Jim

 

[blubuckaroo]

I had one come loose once on a camping trip. Lots of noise but no damage. The crank pulley captured it. On the side of the road, I pulled the pulley and removed the ring. We finished the trip without it with no problem.

 

[DirtDonk]

Drove home from Wild Horses one day in a friend's '74 with one like that too. No damage, and we figured that with the automatic transmission's torque-converter helping to dampen harmonics a little, we were probably ok if we didn't try to enter the Baja or something like that.
Got home fine too, and he drove it around for a few days until he got the new damper.

Prior to it letting go completely, there were not any obvious signs of decay like you would expect. Was not much different from the OP's picture in fact. No rubber bits hanging out of the side, or big chunks missing. Just the usual cracks.
Which is what caught us kind of off-guard. I've seen plenty of engines that had dampers that looked like that (and worse) and they lasted years that way.

You just can't tell. So when in doubt (or whenever doing a full rebuild on an engine anyway... ) just replace it.

Paul