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Discussion Starter #1
Has anybody had this problem? I've broken 2. The most recent one came with a new key. It was firm going into the crank slot. The damper went on tight also. For the first 3 or 4 months the engine was smooth as silk. A couple days ago it suddenly started to vibrate again. I pulled the damper and it is cracked almost identically to the other one down where the snout slides past the front seal and at the end of the keyway channel.

My engine(302) is significantly above stock with ported heads, better intake, carb, cam, exhaust. It wraps up pretty hard. Are the stock dampers from the 70's capable of handling this or do I need to upgrade to a better quality damper?

I'm seriously hoping that it is not something wrong with the keyway slot on the crank because that will be costly.
 

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Discussion Starter #3
6500 fairly regularly. I've been studying this situation and I believe the culprit is the "Made in China" etched on the dampers. In studying the breaks it looks like the cast iron is full of junk. It almost looks like pot metal where it has broken. These might be fine for a totally stock engine. I don't know.

I wonder if a Damper Doctor rebuilt American cast iron one from the 70's would hold up?
 

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6500 fairly regularly. I've been studying this situation and I believe the culprit is the "Made in China" etched on the dampers. In studying the breaks it looks like the cast iron is full of junk. It almost looks like pot metal where it has broken. These might be fine for a totally stock engine. I don't know.

I wonder if a Damper Doctor rebuilt American cast iron one from the 70's would hold up?
The RPM and poor grade materials probably have a direct effect. Normally the rubber ring slips so consider yourself lucky that the balanced didn't come apart. I would certainly be looking at other brands.

Since it hits 6500 pretty regularly, you might consider stepping up to an SFI approved balance. Not sure of what configuration you need, but this 3 bolt pulley SFI balancer was highly recommended to me by a machinist as being a good, fairly inexpensive dampner:

Professional Products 90006 - Professional Products PowerForce Plus Harmonic Dampers - Overview - SummitRacing.com
 

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Discussion Starter #5 (Edited)
I got my replacement damper at Napa and they admitted it was chinese. I would be willing to bet that the chinese ones are not nodular iron. All the familiar name OEM replacements I see online are listed as nodular. I looked up the OEM Pioneer replacement dampers and they appear to all be listed as nodular. I run a re-built( by Damper Doctor) hipo 289 damper on my race car and I run it up to 8 grand.

The addition of my AC and 2 other belts on the crank pulley puts a load on the thing too. I don't generally fling it up hard with the AC on but I may have forgotten a time or 2.

I got back under there last night and got the key out of the crank. I had to pull it with a set of needle nose vice grips because it was in there tight. The crank slot feels good and tight so I'm confident that its not the crank.

"The Pioneer Street Balancer brings bonded balancer technology within the budget of every performance street engine builder. The bonded dampening rubber in every Pioneer Street balancer eliminates spinning and component separation, giving reliable performance in engines up to 6500 rpm's. Pioneer Street balancers combine new high strength Nodular Iron with new inertia rings, then they are bonded and balanced to extremely tight tolerances. Each balancer features easy to read etched timing marks on the outer rings. This also makes them a great heavy duty standard replacement balancer.".
 

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Discussion Starter #7
That Pro Products one is beautiful but I opt'd for the Pioneer one. It should do fine on my truck and it is a bit cheaper. I finally had to go and read up on nodular to understand the difference between that and regular cast iron. Invented in 1943. Interesting reading.

I guess in all fairness to my cheap, made in china, Napa damper it probably was not rated for my "slightly enhanced" engine. I think some of the problem is the speed with which the engine wraps up as well as the top end rpm's. Having the accessories on there doesn't help either because of the extra strain. These are big honkin, heavy dampers too.

This brought up a question I haven't found the answer to. Are all regular dampers made of nodular iron? I am presuming not but I haven't found that.
 

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Discussion Starter #8
The Pioneer damper is a very nice looking piece. I've had it installed now for a week. I discussed this whole damper issue with my machine shop and they reminded me of something I had forgotten.

The damper bolt needs to be torqued to a specific number and not just put on with an air ratchet. In fact, it calls for 90 pounds on a 302. I didn't put nearly enough torque on the bolt for the other damper. Its possible it may have never broken if I had torqued the bolt right. The new Pioneer one is torqued and I also ordered a hardened key to go with it. I don't expect I'll have any more harmonic balancer problems(knock on wood).
 
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