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Old 04-05-2011, 03:59 PM
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SBC Harmonic balancer and crankshaft key way

Small block Chevy. 1974 block, custom harmonic balancer.
Car is a 1986 Pontiac Fiero

There is some slop in the key way, I cant easily pull the balancer due to how the engine is installed.
Now I don't care about the balancer orientation I just need to make it solid again.

The only way to pull the balancer is to drop the engine and cradle, that will take a lot of work and I just don't have the space to do that right now.

I was wondering if I drilled a 1/4 hole in the face of the crank and balancer and installed a roll pin.
I would be drilling into the end of the shaft and installing the roll pin in the same orientation as the crank shaft key.
Would a roll pin be strong enough?

I have good access to the bottom 2/3s of the balancer so I can drill the hole without any issues. Would a hand drill be strong enough to drill the crank shaft?

Thanks for looking.
Jake

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Old 04-05-2011, 04:07 PM
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Are you saying that you can grab the damper like you would a steering wheel and turn it on the crank a little?
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Old 04-05-2011, 04:11 PM
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I can't see a roll pin or other type of pin working. Not necessarily because it wouldn't mechanically hold, but drilling into the gap between the damper and crank snout will be very dicey, getting half the hole in one, the other half into the other- plus being straight on two axes.

What about starting w/an OS woodruff key and carefully taking it down until it was a tight fit into both keyways? The keyway is more for installing the damper so it's phased correctly, the press fit is what transmits the harmonics. So, as long as the damper is still a press fit, you should be OK but be sure there's no "CW/CCW" 'slop'- the damper has to be a press fit.
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Old 04-05-2011, 04:44 PM
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"Slop in the keyway". Does this mean the balancer is moving?.. If so, it's bad and will have to be replaced. Before it destroys the crank snout.

A roll pin will not last. I doubt that a solid pin would either.
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Old 04-05-2011, 04:49 PM
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X2, not if the damper is able to move.
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Old 04-05-2011, 05:20 PM
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The balancer will move on the crank. Its either wobbled the crank or the balancer key way. Its not much and it only does it if I take the bolt out and pull the balancer out about a 1/4 of an inch. If leave the bolt in it has no movement at all.

I will probably have to cut a new key way in the crank. I was just trying to avoid pulling the engine.

Thanks for the input, I will do the right thing and pull the balancer and cut a new key slot and replace the key.

I think its time to cut the frame and fab up a removable frame for just this kind of issue.
Thanks
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Old 04-05-2011, 05:45 PM
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Chevrolet small blocks normally use a press fit balancer. If you can move it around by hand, you have major problems. If it is an aftermkt balancer. It is probably split up the keyway and junk. Aftermkt balancers tend to be too tight and often split on installation.
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Old 04-05-2011, 06:53 PM
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I don't off hand remember what the balancer is made for. Its one that has the belt pulley built into the balancer instead of bolting on the front. This is due to the tight space required to stuff it in the back of a Fiero.

I will update the thread with pictures after I get it fixed or will post what I do with it.

The current balancer will get replace by a new one of the same design.

The balancer isn't spinning on the crank it just has some play in it.
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Old 04-05-2011, 08:14 PM
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There are HTD and serpentine-grooved dampers for various applications, but I don't know of an OEM damper w/a V belt groove. You sure this one wasn't originally smooth and a groove was machined into it? Looks to have been installed w/o benefit of a damper installer, so be sure to use one one the new damper.
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Old 04-06-2011, 01:34 PM
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I don't know what the balancer is for stock but its an OEM part.
What is a damper installer? Mine didn't require me to press it on, it will slide on with a little effort.

The balancer has a key way cut the entire length of it.
I was thinking of getting a new key way cut in the shaft and use a longer key that will have more metal to hold it in place.
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Old 04-06-2011, 05:59 PM
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The key is not what holds the balancer in position ,it is mainly just a guide to get it on with the timing line in the correct orientation for the timing tab. It is the press fit of the ID of the hub to the OD of the crank snout that does the holding.

If the balancer is able to be hand fit onto the crank, either it is bad or the crank nose is undersized out of tolerance. No amount of bigger or better keys is going to solve the problem.

Balancer looks to me like a stock internal balance piece, that someone has machined a belt groove in the OD. No small block ever came with a v-belt groove cut in the balancer, they were always a seperate pulley bolted to the balancer.
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Old 04-06-2011, 06:26 PM
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Quote:
Originally Posted by ericnova72
The key is not what holds the balancer in position ,it is mainly just a guide to get it on with the timing line in the correct orientation for the timing tab. It is the press fit of the ID of the hub to the OD of the crank snout that does the holding.

If the balancer is able to be hand fit onto the crank, either it is bad or the crank nose is undersized out of tolerance. No amount of bigger or better keys is going to solve the problem.

Balancer looks to me like a stock internal balance piece, that someone has machined a belt groove in the OD. No small block ever came with a v-belt groove cut in the balancer, they were always a seperate pulley bolted to the balancer.
Its not a stock v8 ballancer, I believe they came stock on straight 6 cylinders. But it is a stock ballancer.

As far as I know the crank is stock, I don't know if the balancer is broken but I haven't had any issues with it other than the small amount of slop.
I will be ordering a new one form the vendor that sales the kit used to install the V8 in my car.
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Old 04-06-2011, 06:51 PM
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Quote:
Originally Posted by Jake_Dragon
I haven't had any issues with it other than the small amount of slop.
Give it time. It'll fracture the crank. Harmonics (tiny little vibrations) are set up by the bending of the crank from taking the hit from the plug firing an explosive mixture. The crank bends as far as it can from the hit, then bends back the other way as far as it can, then bends back the other way as far as it can and so on until the harmonic is cancelled. If it is allowed to bend back and forth enough times without a harmonic damper being press fit onto the crank snout, the crank will fracture and fail.

The only time you will see a crank last any length of time without using a harmonic damper is on a supercharged motor, like Top Fuel, where they run just a belt pulley on the front of the crank. The large Gilmer belt than acts like a harmonic damper and kills the crank vibrations.

Think of these vibrations as a plucked guitar string.
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Old 04-06-2011, 07:16 PM
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Good lord never mind. I will replace the balancer with one just like it. There are guys that have done this swap and used this balancer for 100000 of miles.
If the crank key way is bad I will have another one cut on the other side of the crank.
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Old 04-06-2011, 07:49 PM
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People are trying to tell you that it is not correct under any circumstance that the damper just slide on over the crank snout. It is designed to be an interference fit.

The deal with the belt grooves on the damper may very well be an engine swap piece designed for your car but, I guarentee it aint suppose to just slip on.

Like said,your damper ID is too big or your crank snout OD is too small,or both.

Bad things will happen if you continue to run it like that. We are just trying to help.
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