heinrich

user error

Tom. M

Nope..can definitely rule that one out...totally paranoid after the first time it happened.. Has to be the harmonic resonance set up with the awesomely powered GT intake and cams..too much power for my block..Probably why mine is the only one with this problem since no S4 even comes close to having as much power...

bolts just quiver at the mention of the 89GT power hahaha lol...

Later,
Tom
89GT

Shark Attack

I had this issue on my 79, found that the PO had the wrong bolts in the wrong holes... He had short bolts were longs bolts were to be... etc...etc....

heinrich

LOL Tom. So you have new bolts. Well we know that this is the first documented case of this phenomenon in the history of 928 ownership, or at least one of the rare cases. And I hear people say metal fatigue or incorrect bolts. You may want to look at the threads in the block. Are they good? Mike S said higher than spec torque would kill the bolts. Well ...... maybe that, too.

Tom. M

Well..a few things in my situation are unique...first is the missing bolt. My assumption of three being OK is probably not correct. Will need to spend some time getting the remains of the old bolt out of the one hole.. Second..sustained high revs on the way over to Spokane..we really haul a$$ over to Spokane..and my motor is pretty buzzy at high revs (anyone else's???). And third the hard hitting engine braking at the track (or using the rolling kick start method)..I am beginning to thing that this hits the tensioner really hard and may be the only cause of the shearing of bolts...with the vibrations loosening them up. All these factors combine to a near disaster..

Either way...my plans are to switch to the Porkensioner, drill out the remains of the bolt ..chase each of the holes and clean them as best possible..pick up 4 new bolts ..torque to spec...and watch very very closely over time. I'm still on the fence over the use of loctite or anti-seize just yet..

Later,
Tom
89GT

heinrich

Tom, the missing bolt - pretty simple - it is there fore a purpose, to spread the load. If there is a missing bolt then the other 3 are unevenly carrying the torsion, and vibration, which will very definitely cause them to fail. In your case, I would say you are lucky they didn't just snap.

Tom. M

Lucky is relative...Both times...one bolt was sheared off (different bolts each time) and one was gone (different each time), and the last one..my savior....stayed in long enough to hold tensioner in place until I got stopped...

The warning system works as advertised..if it's just tension..the light will come on at high revs...and if you stay below that threshold..you are good till a retension....if the light comes on..and you can't cancel...then pull over shut down and hope for the best...

I've used up all my tensioner lives...I will make sure it won't be happening again...that's for sure...

later,
Tom

PorKen

Canadians.

Tom. M

Funny thing is....it's not the Canadians...but your typical SoCal 911 shop...likely saying..yea..we do 928's all the time...we're Porsche experts you know...I mean..how different can the 928 be from the 911????? LOL..

later,
Tom
89GT

ew928

Just back the 928 into the 911 shop. They'll never know better.