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:(.
Any chance the balancer had been pulled off by a mechanic recently? |
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no, I had some wicked vibes from the transmission for a long time until I fixed it a while back. From what I have read the failure path is: Vibration from bad/old mounts causes the bolt to come loose which in turn allows the dowels to move making their fits progressively looser until they finally shear. I had noticed more noise from the engine that disappeared at 900 RPM, looking back it must have been the balancer making the sound. Since I had no idea this was an issue, I am used to working on US V8's, I did not even think to check the balancer bolt. I noticed it was loose, which was I guess my last chance to fix it, when I did the valves 2 weeks ago. I should have torqued it then but I tightened it and forgot about it. seems like a poor design for a joint, but I guess if all is right it will last a long time. not sure why they didnt just make the crank snout longer. I rule of thumb for a good shaft fit is 1.5 times the diameter for the length of engagement. this one is not long enough to be a good joint. |
I'm not sure why they used round keyways, maybe because the section at the shear line is maxxed out without weakening the hub much. The way that they fail is that folks pull the harmonic balancer and bugger up the pin holes when they reinstall.
I am skeptical of drilling new holes successfully because getting a precise hole seems very very difficult to me. When I had the wobbling hb my favorite machinist advised me to get another crank. If he couldn't drill a proper new keyway I don't see how a hobbiest can do it in their garage with hand tools. It doesn't hurt to try though. The alternative is to tear down the entire motor and put in a new or good used crank. Just the labor to tear it down and reassemble is probably 2K. |
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actually I am a journeyman toolmaker. As long as the press fit is still correct the hole is the easy part. I will drill it 1/32 undersize then finish the hole with a correct size reamer. this is SOP for a dowel hole. For location and angle I will just make a small drill fixture to locate and hold the drill bit square to the crank. I will of course remove the radiator and condensor, but I plan to do it in place. Worst that can happen is it fails again. I generally dont drive this car more than 40 miles from home so its not a huge risk, and its broke now anyway, new crank will still be needed if it fails again. |
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got a balancer today. I will mic everything tomorrow and if its ok maybe drill it this weekend. wooowhooo:( |
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looks like the new and old balancer have completely different balance holes. anyone know if this needs to be match balanced at the dealer or is there another avenue
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Personally...
I would match balancer.... hence its name. However, it is not as important as the flywheel, which many do not balance when they do the manual swap. When these engines were assembled, they were balanced as a complete block. IE... the crank, fly, pistons, rods and balancer all go together (in a perfect world) |
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Yeah another wish on success.
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yea, the guy that did my flywheel is really slow. it took him about 4 weeks to get to it. as much as I like driving my jeep to work, it gets 10 mpg and I have a 64 mile round trip. :( |
That sucks... In that time you could build your own rudimentary balancing tool and drill it out yourself.
You can buy sealed bearings really cheap, ps. I hate saying it, but If I didn't build the balancing stand myself and couldn't find a balancer with closely matching holes.... I might just change the seal and hope it did its job. The mass on the balancer is close enough to the center that the forces aren't destructive... but vibration and harmonic amplifications may increase (ie. sinusoidal humming sounds at certain loads). I did the math on someone's flywheel when they had it balanced once. It came out to 64 lbs of radial load @ 2400 rpm (might want to search for that, I could be remembering incorrectly).. anyhow, that was like, 26 grams at 14 inches from the center. I am sure the main crank holders will not have a problem with this, they see much greater forces, correct? In the long term, it IS a stress and could weaken the system somewhere. this is all my own opinion and I would not consider it solid advice. |
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I thought about doing it myself, I may still if the guy wants 4 weeks. Im thinking of just duplicationg the drilled holes on the old one, then counter drilling the holes on the new one to make their contribution 0, I think that would be better then just leaving it as it is. |
very smart. Some simple measurements will allow you to do that very well.
I'd love to see how you do that, please post. |
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