Big Dave

Between the bolt and the hex washer, or between the hex washer and the cam gear? Now that I think about it, I haven't checked whether the hex washer is the washer is moving with the gear.

Bill Ball

That coating has lubricant properties - must be really good friction reducer, as it claims. Manually rotating the engine exerts very little torque (just valve sping tension) on the cam gear.

My reading of the PET shows 55mm shaft length for the bolts, not counting the head. What are yours?

AO

I had to go back and look at Dave's pics. Sure enough that one that looks like it's 40mm in the dial is actually 60mm. I think Bill found your problem Dave...

Edit: On even closer inspection, that dial is all over the map... I think you need a new caliper.

Bill Ball

I rewrote my post a little. The bolt shaft should be 55mm. The 16V engines had 2 different bolts. I'm leaning in the direction of the coating being the problem.

Big Dave

This saga ends tonight. I'm removing the coating, and I have a shortened (by 1/8") bolt...the guys here in the lab at work ground it down and beveled the end for me. If the original bolt is not the correct length (55mm), I'll use the shorter one. One of the two, combined with the removed coating, better fix this situation. I shouldn't be surprised that a non-stick surface isn't sticking.

Big Dave

The caliper is fine. I have 3 measurements...(1) bolt length, (2) hole depth - the caliper has an arm the extends out of the bottom in to the hole which you can't see, and (3) distance between bolt head and cam after the bolt bottoms out. I wasn't measuring the actual distance so much as showing the differences between bolts/cams.

AO

Ahhh... Now I see that the dial is measuing thousandths. Man it must me close to Friday.

Big Dave

I sanded off the non-stick coating from the hub surfaces, used the shortened bolt, and the slipping has STOPPED.

sendarius

I'm glad that you solved it, but what worries me is that there seems to be no locking mechanism between the cam and cam gear.

Surely it is critical that Mr Valve not meet Mr Piston, and even in the non-interference engines, performance is NOT going to be good if the valve to crank timing changes as the cam gear moves wrt the cam.

What am I missing here?

Steve

GregBBRD

If a bolt bottoms out in the bottom of a tapped hole, the threads at the bottom of the bolt get damaged....it is easy to see and would be obvious. Also a bolt that bottoms out, feels a whole bunch different when you try to torque it, since the bolt twists the entire length, from the bottom where it stops. The difference in the feel, as one attempts to torque the bolt is very obvious. So, I'm not buying the bolt being too long for the camshaft.

That means the coating on the gear is so slick that there is not enough friction to clamp the gear to the drive hub....interesting to think what happens when the belt touches this slick surface and tries to turn the camshafts.....

gb

Big Dave

I've already got 5,000 miles on these coated gears. Besides, the gears have a similar coating on them from the factory (on the teeth only), designed to reduce wear on the gear teeth. When that coating is gone, the metal begins to erode and it's time for a new gear.

Here's an eroded gear, incapable of being salvaged with a new coating.

Big Dave

Each time the cam gear slipped, it was stopped by the woodruff key. We've all got the same setup.

I agree that the engine would run like @#$@ if the cam timing slipped. That's why I had to stop it!

I blame the coating here. It had glazed over on the contact surfaces.

Randy V

Bed time, Dave.

SwayBar

That was a very interesting thread; congrats on solving the mystery.

AO

Awesome!

Now, it's a marathon weekend for you. You need to drive it this weekend to get some miles (and confidence) before Hell.