Well, the crankshaft pulley on my '78 280Z is wobbling. Doug Bakke of Awesome Z in Houston noticed it as he was looking at a couple of other items for me (fuel pressure and lines). We're hoping it's not the end of the crank itself, but just the pulley/bolts/rubber. Pulley is on it's way, so I'll find out soon.

Is the pulley wobbling, or is it crank run-out?

Don't run the engine anymore (obviously). Inspect the keyway upon pulley removal, likely it is worn to the point where the key is loose and you need crank repair or a replacement. The pulley is likely wobbling because the bolt has worked its way loose. Has it been disassembled fairly recently? Use loctite next time.

Don't run the engine anymore (obviously). Inspect the keyway upon pulley removal, likely it is worn to the point where the key is loose and you need crank repair or a replacement. The pulley is likely wobbling because the bolt has worked its way loose. Has it been disassembled fairly recently? Use loctite next time.

I came across an interesting discussion on this topic over on Hybridz a while ago (link below). Apparently the keyway is mainly for initial indexing, not holding the damper/pulley from rotating out of sync with the crank. The force locking the damper/pulley to the crank comes from the compressive force of the bolt on the crank end. So minor damage to the keyway should not necessitate crank replacement or even repair, if you can live with the knowledge that slot is not straight anymore.

Not perfect but might save you some time and money. It's worth a read.

Post #21 summarizes pretty well.

http://forums.hybridz.org/index.php?/topic/91212-cracked-crank-pulley-worn-woodruff-keys-crank/page__st__20__p__872134__hl__crank%20keyway__fromsearch__1entry872134

It could just be the rubber. I've seen that happen before. Somewhere there's another thread about this.

I'm not driving it; I have it at the Z mechanic Doug Bakke, of Awesome Z. He's seen these problems many times over his 40 years working on Zs, and explained several causes, one being a problem with the crankshaft itself. I'm hoping it's anything but that, as I'm not due for a rebuild for awhile. I'll post details on the problem and solution.

Edited June 2, 201014 yr by Davey G

I've had the vibration damper rubber on the pulley get old and break causing the hub on which the belts ride to move in and out Buy/rent a vibration damper puller at the local parts store to remove and replace it. Don't use 3 jaw pullers, or makeshift means to remove it and don't use a hammer to install the new one. Use the proper tool, otherwise you might damage the new one.

He has a mechanic working on it but it doesn't matter what tool you use to remove it if it's already damaged and the bolt itself can be used to install the new one.

I've had two friends have vibration damper failures on 2.8L engines. One is a stock '75, the other is a 3.1 stroker. Both wobbled as you've described. A new or refreshed damper solved their issues. I hope it's as simple for you!

Frank

He has a mechanic working on it but it doesn't matter what tool you use to remove it if it's already damaged and the bolt itself can be used to install the new one.

But if it isn't the culprit and you don't use a proper tool to remove it you may pull the hub from the center section and damage it. If that wasn't the problem it is one now and an additional expense. If you rent the puller you get the installation tool. O'Reilly's and AutoZone have free tool rental, so it's no big deal.

Well, I suspect you're in good hands. Tell Doug I said hello and 'see ya' in Nashville.

But if it isn't the culprit and you don't use a proper tool to remove it you may pull the hub from the center section and damage it. If that wasn't the problem it is one now and an additional expense. If you rent the puller you get the installation tool. O'Reilly's and AutoZone have free tool rental, so it's no big deal.

Relax, note that I said IF. And you'd be able to tell if the rubber was bad easily enough before you put any tool on it. Besides, I don't need to rent the proper tool as I already have one as I imagine Doug does also......