Peter F

How about over tightening that bolt, could it cause similar disaster?
I remember when doing my TB and WP I was nervous tightening that bolt but did end up using the WSM moment number.

/Peter

Mrmerlin

I would think that if the proper torque was followed the cam should work fine , unless there is another problem in the head causing the cam to lock up

SeanR

Got pics of the bolt, will update this evening.

SeanR

Just measured the bolt, measured another one and the one that was in Docs car elongated by 1.5mm.

ROG100

The bolt shows elongation in the threaded area - what does that tell you Colin?

Lizard928

it is possible the wrong bolt was used (able to check thread pitch to confirm if it was elongated), and that it bottomed out in the cam preventing proper tightening of the cam, this would probably show signs of wear on the end of the bolt (threads). Just to interject here, Sean, you know when measuring a bolt you are NOT to measure the head in the total length right?
But even if too long of a bolt was used that bolt would have normally been sheared off, or have a pretty serious bend in it. If the cam were to break with the proper bolt being properly torqued then you would see serious wear to the washer, the reason for this is that when the timing belt is turning, should the cam snap the extra drag on the bolt/washer would try to tighten it more.
You can also see that this cam gear quite obviously did get cocked off the head, meaning that the bolt would have been bent. And that extra force, and stretch should have simply snapped the bolt.

I will hold off further comments on it until I see a picture of the bolt, preferably right next to a correct bolt.

docmirror

Ok, I've been on a hunt for the info I need, and it looks like things are going to go back together someday. I have sourced a cam, and found a person who can grind it right. I've got the machine shop that can replace the bent valves, and I'm going to grind the seat back some on the exhaust, or use a lash cap to get the lifter to the proper height. I'm leaning to grinding the seat, as I don't like lash caps but I'll do what's best depending on the machinist recommendation.

Now, under the heading of 'it suckes to be me' in October.

Porsche repair bill - $1300 and climbing, maybe over $2000 when finished, just found out my LH went T.U. so the hits just keep on coming.
Airplaine repair bill - $2300 and climbing(transponder, nav antenna, prop motor controller, gear service)
Durango - $370. Drivers window regulator, glass and install.
Ram truck - $450. Body work from a guy backing into me in a parking lot(spring), and bumper repair.
VW Golf - $117. Trans filter and new lube.
VW GTI - $488. Timing set, trans filter, lube, headlights, O2 sensor, brakes, various seals.
Jet ski - $49. Battery(in Sept, but close enough)
Ferrari - $775. Wheels, no tires yet. Also needs new belts and bearings this fall.

My wife is screaming mad, and with good reason. We like the toys but this has been - brutal. And no, this is not a plea for some paypal help, I'm a big boy, and can afford the damage. Sat 10/25 We're going to a fly-in so no engine party. I'll be getting the car home tomorrow and I'll slog though the damage this fall. Maybe in late Nov I can host a Turkey day assembly and feed some folks. Depends on the timing of the shops though.

As for the cam. I know it was the right bolt, and it was torqued in. Once I get things apart further, I'll see what happened. The guy at Elgin said he's seen it before due to the exhaust cam driving both cams via a chain. Puts a lot of tension on the hub area. All speculation so far.

Jim bailey - 928 International

Greg Brown has mentioned before that the Hub 928 105 459 00 the three legged part that the cam gear bolts to can get cracked and since it alone has the small indexing keyway once it breaks the Cam gear has a much wider slot (for the abilty to adjust) . Now the bolt is all that can keep the cam from walking back and forth on the too narrow key. I believe he said he has seen this cam breakage several times before. He replaces those hubs when doing timing belts especially if the car has bent the valves.

the flyin' scotsman

Gotta wonder how many cams were timed with Porkens inventions with no issue.

Any more pics Sean?

SeanR

I do have, but the camera is conveniently sitting on the fender of said car.

Lizard928

Really keen on seeing pics of the bolt, I missed Roger's post before stating that the threads were elongated.

If this is the case, then the bolt would have had serious force on it as it somehow backed out.

SeanR

Could this be caused by what Jim was talking about on the Y?

Lizard928

Yes that is possible Sean,

I would like to see how much of the threads are stretched though, and when you dove into it, was the bolt free, or was it still partially threaded in?

Reason being is not all the threads actually are used on the bolt, and when the belt is turning it would move the bolt in a tightening fashion, and it should not back off. But even if it is abit too loose it would excentuate a crack in the Y causing it to fail even quicker.

SeanR

Wasn't loose before or after. With the way it was all torqued over it was hard as hell to get out. Doc said he was going to pick the car up today to take it home but I've not heard from him in a few days.

Lizard928

Ok, with that bolt not being loose or coming out easily, I would have to say the most likely source of the failure was the Y piece failing. I would still like to see pics of that bolt!