this didn't happen to me but, i've seen this mentioned many times from people after a cam swap, is this because of not installing a new crank bolt and following the gm torque procedure, what's the bottom line here for a secure pulley?

 

LS1/LS6 pulleys are tapered to fit the tapered crankshaft. A single use bolt holds them together. Sometimes that bolt comes loose. Sometimes just the force of the belts overpowers the tapered surfaces. When the bolt comes loose the pulley will move forward and spin on the steering rack and make a grinding noise. If that takes place for too long it can wear the inside of the pulley down thus taking away a thin layer of metal making re-use of the pulley impossible. Purchasing a new pulley and installing a keyway between the crank and pulley is the most desirable thing to do.

Personally, I purchased an ATI crank pulley (same pulley all the NASCAR engines run) with an 8 rib surface, had that keyed and installed on my new blower motor. No problems since even while running a Supercharger.

VR

 

What about wobble on the crank / harmonic balancer pully? How much wobble is bad vs. acceptable?

I've noticed on the inside portion of it, which looks to be surrounded by a rubber seal that it looks like it wobbles about a 32nd or 16th of an inch.

The steel pully that the belt rides on is rock solid though. Can't really make out if this is something to be concerned with or not. Car only has 900 miles on it now and been like this all along.

Thanks,
Sean

 

My factory pulley had a wobble too and it worked just fine. Doesnt seem to be a problem for a stock motor.

VR

 

The harmonic balancer is held on with 3 friction surfaces.

1. The balancer has a tight tolerance fit onto the crankshaft. Its a straight press on fit. There is no taper.
2. The balancer mates up against the crank sprocket. This sprocket drives the oil pump and the timing chain for the cam.
3. The flange of the crank bolt mates up against the balancer.

Those 3 mating surfaces play a vital role in keeping the balancer properly installed.


What will cause the balancer to come off:

1. The crank bolt wasn't torqued properly.
2. The balancer didn't have a tight enough tolerance fit when it was pressed onto the crankshaft, and started rotating on the crankshaft which in turn could loosen the bolt.
3. The balancer must protrude out beyond the crankshaft snout. If it doesn't, then the flange of the crank bolt will be gripping onto the end of the crankshaft snout and not the balancer which in turn could cause balancer to start "walking" and could cause the crank bolt to loosen.
4. A new crank bolt wasn't used upon reassembly after some modification/maintenance. If you were to use the old crank bolt again, you risk the possibility of stretching the bolt too much which could cause it to weaken, snap, or cause a hairline crack only to break later.

The crank bolt is a "torque to yield" bolt. The term "torque to yield" means the bolt will stretch to achieve the proper tension on the component to which its installed. In other words, the crank bolt has kind of an elasticity to help hold the balancer on.

The pic below shows a cutaway of the balancer assembly. As you can see, there is a gap that shows where the balancer protrudes out beyond the crankshaft snout. This is so the crank bolt will mate up against the balancer to help hold it on. Like previously mentioned, if that gap wasn't present, then the crank bolt would tighten up against the end of the crankshaft instead of the balancer. You can also see where the balancer mates up against the crank sprocket and where the so called "washer fix" would go for the C6's that are having this problem.

My balancer in my 02 Z06 has a very slight wobble and almost not even noticeable. I pinned the balancer in mine when I installed the supercharger and never had a problem before or after the pinning. That was 15,000 miles or so ago.

Hope this helps explain a few things.

 

SO, is the shaft tapered or not. If not is it an interference fit? Meaning the shaft OD is larger than the pulley ID.
Inquiring minds wants to know!

 

Its not tapered. It is a tight tolerance/interference fit. When assembling that area, you would first slide on the cranksprocket, which will butt up against the crankshaft. Then you will slide on the balancer, which will butt up against the cranksprocket. Then install the crank bolt. Here is another pic below that shows the crankshaft with the cranksprocket installed but without the oil pump and timing cover.

 

SO, that answers your question??

VR

 

Dude, I was just showing a pic of it. Not that its supposed to prove there is no taper. But there isnt anyway. Its a press on fit.

 

If you use the proper tool to seat the pulley (don't use the old bolt to seat the pulley), follow all torque specs, and use a new bolt, you should not have problems. If I take mine apart again I will pin the crank for extra insurance.

 

it's the texans', always the texans', it seems like all the hardcore people live down there, respect is given, thanks very much for the detailed response, looks like people(northeners) are installing the pulley so it's flush w/ the crank, NOT the way it's done by the book

 

Tank U Velly Velly mulch!
I deal with machinery and I just couldn't see a tapered fit with out having a Key. And how much money do they save by not installing a key?

 

It appears that a keyed or pinned crankshaft damper wasn't on the list of 80% redesigned parts for the C6.

 

Its ok, I dont have a problem with you chiming in with info and pics on this topic. I am glad you did because it really helped the members out with learning more about this subject than what I had already explained.

VR

 

Does pinning a pulley cause there to be a wobble in the balancer due to the weight of the pin? I guess it really wouldn't since you are drilling out metal and replacing it with more metal...hmm...