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View Full Version : Anyone ever repaired a harmonic balancer/crank pulley?



winchman
07-28-2010, 04:43 PM
It's off an old Datsun 240Z straight six. The bore is supposed to be a press fit on the crank, which measures 1.378" in diameter. The bore is wallowed out to about 1.405", and the keyway is messed up pretty bad. Pics later.

I'm thinking about boring it out and putting in a sleeve thick enough for a new keyway. The material looks like cast iron, but I'm not sure yet.

What's the best way to secure the sleeve to the original part? The bolt on the crankshaft will press on the end of the new sleeve to get it on. However, the holes for the puller are on the original part, and I don't want the sleeve to pull out if it ever has to be removed.

How much of a interference fit normally used on parts like this? The pulley has two V-belt grooves, so I think it's driving something besides the alternator and water pump.

Of course, the timing mark is on the pulley, so the alignment of the keyway is somewhat critical.

Any suggestions will be appreciated.

BillTodd
07-28-2010, 04:53 PM
Shrink-fit the pulley onto the sleeve before you machine the new bore and key-way (i.e. cool the sleeve & heat the pulley). If you are worried about it pulling off, machine a shoulder on the outside of the sleeve, with a matching pocket on the pulley .

Bill

Doozer
07-28-2010, 05:05 PM
I would be very surprised if you could not buy one at a reasonable price.
--Doozer

Ian B
07-28-2010, 05:35 PM
Hey Winchman,

Doozer's absolutely right - you could probably buy a new one for peanuts.

But that's not the point - we're HSM'ers, and we spend a fortune on machines to make an 1 part! I've being doing that for years...

Go for it - fix the old one, post pics, tell us how you did it. *Much* more satisfying than buying a new one.

Ian

strokersix
07-28-2010, 05:39 PM
Dampers can be dangerous if they come apart at speed. If the bore is that wallered out, what's the condition of the elastomer material? Tread carefully.

I would be comfortable with an interference fit probably about .001 inch on diameter if it's similar design to vintage GM engines especially if it's retained with a cap screw.

fasto
07-28-2010, 05:56 PM
A 240Z will only have water pump and alternator for accessories. There is a *very slight* chance that it has air conditioning. Power steering was not offered. It might have originally had a smog pump but most of those have been removed & thrown out over the years.
Personally I'd put a wanted ad up at zcar.com. You'd probably have one tomorrow for $20.
I checked the 280Z factory manual and there's no spec for the crank nose diameter, pulley ID, etc. I don't have the 240Z manuals.
How did this pulley get so worn out?

datsun280zxt
07-28-2010, 09:33 PM
I too would say this is not a part that you probably want to repair. These pulleys separate over time, and if it has much age (or is the original damper), it's time for a replacement. How bad is the end of the crank and the keyway? You mention some keyway damage, is it going to be repairable with the crank still installed? Is this a fairly stock car, or is it something that sees a lot of rpm? If it's not stock, there are some good alternatives for aftermarket setups. If you don't have any luck on zcar.com try hybridz.org and post a wanted ad.

EddyCurr
07-28-2010, 09:46 PM
DamperDoctor does not appear to list parts for Datsun/Nissan but it
might be worthwhile to write for advise and to ask whether they
handle this make on a special order basis.

.

winchman
07-29-2010, 12:29 AM
I'm pretty sure the crank was replaced during the rebuild. What's in the engine now has no damage to the part where the balancer will fit.

I'm a little concerned that there may be too much flex in the rubber to get a good finish on a new bore. There's no place to get a good grip on the hub in the 4-jaw. There are several small tapped holes around the hub that might be used to attach a piece for chucking. I'm not sure what their original purpose was.

I wanted to at least research the machining issues before telling the fellow to go looking for a replacement. Thanks for the suggestions and cautions.

doctor demo
07-29-2010, 12:38 AM
There are several small tapped holes around the hub that might be used to attach a piece for chucking. I'm not sure what their original purpose was.

Those tapped holes are probably for pulleys for different model or accessories.
Re-builders that I have talked to in the past seem to have a long lead time , but that was for old Chrysler stuff .

Steve

JoeLee
07-29-2010, 07:06 AM
I would be very surprised if you could not buy one at a reasonable price.
--Doozer

I agree.......... the local junk yards should have a good supply of parts like that. Why wast the time.

JL....................

wierdscience
07-29-2010, 08:02 AM
Those tapped holes are probably for pulleys for different model or accessories.
Re-builders that I have talked to in the past seem to have a long lead time , but that was for old Chrysler stuff .

Steve

Yes,they used that engine in various incarnations over the years.Good engine too.

spkrman15
07-29-2010, 08:09 AM
Roger,

I would try to look for a replacement, yes you have heard it already but here are somethings you will have to consider as you fix the balancer.

1. you shouldn't heat it to do the slip fit. There is rubber sandwiched in between the metal. I am assuming it is not an all metal balancer. Heating the metal might affect the bond of the rubber to the metal.

2. Lots of rotational forces (5000-7000 rpm?). The balancer will have forces affecting it in two planes. I pretty sure the blancer will try to woble on the shaft, putting lateral forces on your new bushing. It will also try to make the blancer come off the crank shaft or go in towards the engine which will try to push in or push out the bushing.

What i would do?

I would try to pin it in two perpendicular planes. This would be after i used dry ice to shink the new bushing in. I would also have put the balancer in the hot sun and let it warm up that way. If i could i would make the pins long and swage the ends so they don't come out. Remachine the bushing and keyway. THEN send the balancer out to be rebalanced. No point putting an off balance part on a motor that is supposed to help "Balance" the motor. Yes i know some blancers are off balance to counter the harmonics of the motor. I just don't know if this one is. Alot of things to think about and consider when you can just get a used one for maybe 50.00. One hour of my labour!

Then there is the other school of thought.
Bore it out. Machine bushing, loctite, press fit, etc, in. Machine new keyway, install on crankshaft and go for it.

Good luck.

Rob :)

winchman
07-29-2010, 12:23 PM
I returned the balancer this morning, and I explained my concerns about doing the job. Turns out the fellow had already purchased a replacement for it, but had dropped it on the concrete floor shortly after unpackaging it, and a sizable piece of the pulley broke off. Bummer for sure, so he wanted to make sure the original one was beyond hope before getting a second replacement.

At least he knows where to get another one, and that's what he's going to do.