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Old 04-30-2007, 12:27 AM   #1
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Default LN3 harmonic balancer issue

Hey guys. I'm back, and dealing once again with my LN3 block/internals dressed as a Series 1 L67...

As we left off, my harmonic balancer keyway and key were really chewed up. This created like a 1'' timing offset (don't know how many degrees that is), making the engine feel like it had 30-40 hp or so. Don't know if it caused any other damage inside. Anyway, as I understand it, the issue is that an LN3'* rotating assembly is internally balanced, while the L67'* rotating assembly is externally balanced.

The L67 is not balanced without the harmonic balancer. Neither the rotating assembly nor the balancer are balanced by themselves, but are balanced with each other.

With this being known, my issue which lead to the eaten up keyway/key and the vibration at idle are due to the weight of the L67 balancer on the LN3'* rotating assembly.



The L67'* balancer is on the left, LN3 on the right. Notice the "hammerhead" weight of the L67 and how much bigger it is.

I spoke with the owner of Dale Manufacturing, a rebuilder of harmonic balancers and Corvair parts dealer (if you're into those...). I described my issue and what I wanted, pretty much that I wanted an L67 balancer than acted like an LN3'*. He couldn't like build me one, saying that they're pretty much a one piece assembly and are already difficult to rebuild. At any rate, we got talking about the "hammerhead", and how in theory, though not a precise operation, I could Dremel the L67'* hammerhead, make it about the size on the LN3'* by eyeballing it, and I would be set. The L67 balancer does have some holes drilled in it for added balancing, which I will take into consideration. It won't be precise at all but I'll be a lot better off than otherwise.

Any comments? Thanks guys.
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Old 04-30-2007, 03:45 AM   #2
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Default Re: LN3 harmonic balancer issue

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Originally Posted by F14CRAZY
Any comments? Thanks guys.
Hmm..you are looking at this bass-akwards. Instead of trying to make/modify the harmonic balancer, you take the entire rotating assembly to a machine shop and have it rebalanced. They can slug the crank to get it balanced using the L67 balancer. That'* plan A. Definately call around first. You might find, as I did, that few shops have the bob weights for the V6 journals.

Plan B - Have a machine shop make a serpantine belt pulley that stacks on top of the existing LN3 harmonic balancer...so you get the second belt drive without using the double row L67 harmonic balancer. This isn't as hard as it sounds. A billet aluminum pulley is pretty easy to make. Pins can engage the existing balancer to drive it, and a longer crank nose bolt can hold them both in place.
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Old 04-30-2007, 08:00 AM   #3
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Let'* not forget about the offsetting weight. The flywheel. At least in the S2, and I'm not sure about the S1, the flywheel has a serious weight on it as well to work with the harmonic.

Now..with the exception of needing an second belt path.. you want to keep your LN3 balance characteristics from what I would assume. Otherwise.. you are putting the wrong balancing on a motor that wasn't meant for it.
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Old 04-30-2007, 09:16 AM   #4
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Plan B sounds good. I wish I could have thought of that myself, but that'* why I turned to the infinite wisedom of BC . I have a good, cheap machinist that could pull that off. The modifications to the LN3 balancer wouldn't change its characteristics, would it?
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Old 04-30-2007, 09:18 AM   #5
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It will lighten it slightly, but shouldn't upset it'* balance by much.
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Old 05-01-2007, 12:28 AM   #6
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Thanks guys. I'm gonna be looking into the "cap" idea to add the second pulley drive to the LN3 balancer.
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