88 S4.

SO..my main crank pulley bolt came out hours before leaving for SF12.

It was maybe only 30 seconds of run time, but there was enough damage to destroy the pulleys, and the bolt.

When the bolt came lose the pulleys swapped a lot of metal between the faces where they meet. The AC pulley actually got a little of a bell lip too.

As the bolt came out, the pulleys rode on it's threads, which made it a mess..unusable.

Got used pulleys from 928int, a new bolt and a new washer for it.


There is a little damage on the crank snout just at the edge..some scratching, and a slight lip at the very end..working to slowwwwly sand that down by hand so the pulleys slip on even but snug.


Bleh.




VERY happy I still made SF12, still only said "hi" to maybe half the people..so much going on.

 

Emory cloth on the snout.

 

Yup, best roll of magic in the toolbox.

 

Not sure what would cause the bolt to back out if it was torqued the last time it was installed.
Probably worth checking the O.D. of the crank snout & the I.D. of the new SC pulley & compare to the I.D. of the stock pulleys (or however it mounts) to see if it centers properly.
When assembled, couldn't hurt to check the runout of the pulley assembly in both directions (radial & "wobble")with a dial indicator. Something shook the bolt loose. Could be real ugly at redline if it got loose again.
Is the SC pulley hub wide enough that you really need a longer crank bolt when added to the stock pulleys (not sure how it assembles -no pic)?
Hope it's fixed.

 

This car is supercharged. There have been quite a few reports of crank bolts backing out on 928's with significantly more power than stock. At one point I think there was a longer crank bolt made which mitigated the issue?

Dan
'91 928GT S/C 475hp/460lb.ft

 

Jim, its Victor's rotrex kit..uses the stock pulleys, and runs from the alternator belt.

 

Haven't seen pics of the install, but no added pulley
is one less thing to go wrong- a good thing.
Hope you have it fixed.

 

Very often when the bolt works its way out it's due to the washer being installed backwards. The washer is concave and the curve must face out or against the bolt head.

 

So, either you need a good new torque wrench or the old crank bolt got streched.

 

Down 'smooth' to where things juuuust fit.

 

That looks bad, How much tension did you have to put on the supercharger belt. Did you have any belt slippage for the Rotrex super charger causing you to put more tension on it? That could have caused the bolt to come loose or you didn't use a torque wrench last time you did the T-belt job or if you did use a torque wrench it was way out of calibration. How does the new pulley fit? Is it snug against the crank or does it have play? If it has play you may need a new crank.

 

You can't over tension the belt for the supercharger. The alternator adjustment runs out before the spring tensioner does.

 

No slipping, its been fantastic. And as sean says, not possible to over tighten it..in fact, its a little loser than what most of us have the plain alternator belt at by itself Id guess.

New pulleys are snug.


NOW..how the heck to measure out 218FtLbs on this biatch....


Im 295..use my ~foot long 1/2" wrench on it and..well..stand?

 

What do you tighten if the belt is slipping? Do you use alternator adjusting bolt or does the SC tensioner get adjusted manually? Have you used the Porsche belt tensioner to see how much tension you have on your SC/alternator belt. I think WSM has specific values that they need to be set at. I think I saw a picture of it on WSM.

 

I think the WSM says torque value needs to be at 218 FT/LB. I set the wrench at 220. Go rent two torque wrenches from two different stores (Autozone, Pepboys, Orilleys) and compare them.

Make sure they have a date on them showing the last time they were calibrated. If it was calibrated back in 010 then go to another store.