byrdman454

Isn't that hex washer cupped a bit? The cupped portion should face the cam gear so that as the bolt tightens against it, it flattens out and bites the gear. If it was flipped over with the cupped portion toward the bolt, it would not flatten out and bite into the gear. This would allow the gear to slip.

I am going from memory, so the cupped washer feature might not be accurate.

Big Dave

Interesting...if true, I'm sure this could play a big role. I didn't try reversing the hex washer. Anyone know for sure if the washer is cupped?

PorKen

The washer is flat. BTW, the bolt is 55mm long on 32V engines - the torque is 47ft.lbs.

Was the hub on the damaged cam? If the hub is expanding under compression, you should be able to see the crack.

Big Dave

Thanks for clarifying the washer. By "hub" assume you mean the item pictured as #2 (referenced as a "dog" in the manual). Yes, it's the same one I used on the damaged cam. I need to inspect it. If it's cracked, it could easily be compressing and allow the slippage.

AO

So...?

Big Dave

Using a dial caliper I found some interesting differences, but I'm not certain whether they're causing the problem.

1. The "new" cam I am using has a slightly shallower hole.
2. The two cam bolts are not the same length
3. The dog gear behind the cam gear is not broken, but I replaced it anyway.
4. The cam gear is not broken, but I replaced it anyway.

I used the shorter bolt with a different dog and cam gears. This time the cam timing stayed in place for 2 full (360*) revolutions of the crank. It slipped again on the third trip around.

I'm cutting about 3/8" off of my cambolt and trying again tomorrow.

jpitman2

I hope you meant 3mm , not 3/8" , or 10mm????
This sounds as scary as stripping a head bolt thread in an alloy block.......camshaft noses have been known to break off, but usually on a 16V engine. With Ken's stuff, isnt the thickness of the dog less for those that fit a 16V car? You dont have one of those do you, or this not relevant?
jp 83 Euro S AT 50k

69gaugeman

Dave,

In the second last picture, take the washer and install it just like you have now. Then measure from the dog face to the washer. Then take the cam and measure the thickness. There should be a difference of at least 3mm (the space between the washer and the dog face should be minimum 3mm shorter than the width of the cam gear)

Big Dave

No, I'm only taking off 1/8" of an inch. That should be more than enough, and should leave enough left to torque properly.

Not sure about the 16v dogs. I actually have 2 spares, and they are all the same thickness, including the dog currently on my cam.

Imo000

Before you cut anything, get another washer (same or close to the same thickness as what you are planning on cutting off) and install it with the original washer. Then do the rotation testing and see if the timing stays put. If it does then you know the length of the bolt is the problem and you can safely trim it. If not then at least you didn’t cut the bolt for nothing.

Big Dave

I have 2 cam bolts available....only cutting 1 of them. It's nice to have spares.

That's a good idea, though. I'll give it a try.

heinrich

Dave shouldn't we be wondering why the cams are different? Ar there other differences also?

Big Dave

Good question. For the record, the old cam is original to my '85. The new (to me) cam is from an '86. I was surprised that the '86 cam had a slightly shallower depth. We're only talking .02", but the difference is there. It may be within normal tolerances. Again, I don't know whether this is a factor.

What's interesting to note is that I have been using cam gears that were re-coated to replace the original finish that was eroding. That recoating covered the entire gear (including the back of the gear which has a very sublte textured spiral finish). I had no slippage issues whatsoever using this recoated gear when I did the last engine pull/fix. Rather than wonder whether this coating is contributing to the slippage, I'm sanding it off of every surface that will have clamping pressure from the cambolt and dog gear. Together with a slightly shorter bolt, this ought to stop the slipping.

AO

I know people are going to ask...

https://rennlist.com/forums/928-forum/219673-melted-cam-gears-pics-not-for-the-squeamish.html

The coating is DFL-1 - you can find it here. http://www.techlinecoatings.com/Engine.htm

heinrich

I wonder if a simple sprung washer would be OK? Or a toothed washer?