These pads were replaced today along with the install of an updated chain. I thought it was interesting to compare the first picture taken around 5k miles ago versus todays pictures at 63k miles with the pads off of the car. I was surprised by how much wear they have.

5k Ago


Today


and

 

Do you think it has to do with staying in the variocam range a lot? I find that about 80% of the time I am below 4k rpms, but I am at way more mileage than 5k and I don't have near that wear on the top atleast.

Wes

 

Bruce,

Before I bought my car at 64k, it had the variocam pad break, and it took out the cams and valves with it...scary thoughts. It is weird how they can wear so quickly.

Steve

 

I think the wear at 58k and 63k was similar but it is more difficult to see with the chain over the pads. From now on when I change the belts I am going to change the pads and chain as well.

 

Bruce,

What about every other belt change? I would think that it's a 60k service item....how were your cam teeth?

Steve

 

I think if the car is driven often, then a 60K or 4 yr inverval should be followed. It seems its the balance shaft belt more than the timing belt that has been doing the damage. I just saw another car with a broken bb belt which took the timing belt out with it.
Bruce, maybe 60K or 4 years would be a good interval for the chain and pads.
Raj

 

Couple things:

1. About a year ago here on rennlist i had a big argument with someone about the bb belt taking out a timing belt - he said it will never happen, i said foooey, they do take timing belts out. Hehe, i was right, so eat crow whoever you were....

2. I think there are a lot of variables to cam chain tensioner wear - kind of oil, composition of the tensioner (what kind of plastic is it made out of), how often do you take your car past the 4K mark, how HARD and FAST do you take your car past the 4K mark, to name a few...

3. BruceWard - how are you going to change the pads and chain so often? Are you cutting the chain and installing a new one, or are you taking the cams out and doing it that way? If breaking the chain, what's your source for the 'breakable' chain...

4. I'd like to see a little more conversation/comparison here about the various sources for the tensioners and what they are made of.

Later all!

 

My 968 has about 70K miles, about 4k by me. When doing my t belt, rollers, and WP, I also planned to replace the variocam chain and pads....and bought them. But when I took the cam cover off, everything under there looked good as new so I left it. My pads had hardly any wear like you're showing. I don't know if the PO replaced anything or not. The car is in great shape everywhere so it's been well kept.

H2

Harvey

 

Harvey, do you still have those pieces, if so I can buy them off you. I need them for a friend.
As far as people not believing a balance shaft belt taking a timing belt out with it, I will post some pictures shortly.
Raj

 

I just replaced my hall sensor, and when I removed the VC my pads and chain looked great with 100k. Most wear takes place on the lower pad. I am replacing my chain and pads for good measure
before a problem arises. I frequently see 6k thru 4th gear!

 

I was thinking of a pad and chain change every 60K unless the new version of the chain eliminates or reduces this problem.

If the pads fail the cam(s) will fail causing the pistons and valves to meet. The cost to repair is the normal $3K to $5K for a timing belt failure plus $1200 of cams. So in my opinion it is worth while to change the pads and chain proactively.

I purchased all of the parts, removed the head from the car and then worked with factory trained mechanics (Perfection Plus) to rebuild and reassemble. I took them the head a week before the car. The head received replacement Porsche valves from a spare head, a valve job and thorough cleaning.

The head looked like this afterwards



The pistons, bore and cam cover were all cleaned just as well []

Since the timing belt had been broken by the balance belt my cams were no longer timed to match the bottom end there was no point in trying to preserve timing. The pads and chain were changed with the cams out of the head. The only way I can see that they could be changed while installed in the head would be with a chain with a removable link. Although I do not think much time or even timing effort would be saved this way.

It is possible to retime the cams less precisely without doing so but I chose to go to the pros and have the cams retimed using dial gauges to the factory spec. To do so you need a dial gauge for the intake cam, one for cylinder 1 and to be able to force air into the variocam where oil would normally flow. Without the variocam pressurized with air the reading on the dial gauges changed by 1/3rd. Using this setup the cams were timed perfectly and based on the witness marks probably better than they came from the factory.



When I change the timing belt again I will inspect the pads. If they show wear I will change them and the chain with the cams removed from the car. I am undecided whether I will mark the cam to sprocket alignment and retime based on that mark or go for the dial gauges again. Most likely I will opt for the dial gauges.

The 968 now runs stronger than it has since I bought it []

 

Bruce,

I didn't know your belt had snapped-at least this was a good excuse to have your head done and do the variocam service! Sorry to hear about the misfortune...

Steve

 

If you look at this picture you can see the balance belt in the wrong place



The balance belt had broken and doubled up following the timing belt up to and around the exhaust cam sprocket.

 

Hehe - thanks for the pic! I'll print it out and save it for future arguments with wannabees...

 

Raj,

I'm saving the Timing chain and pads for the 100K mile update. Rather than invest in stocks, I'm buying and stockpiling 968 parts, figuring the prices will rise in value faster than Dow Chemical. Just today, I got in a used fuel rail, extra set of injectors, and a complete engine wiring harnass. Will I ever need them? Dunno. If I don't, I can always sell them. I've noticed 928 parts going up in price or becoming NLA. Figure the same will happen to the 968.

Only time will tell how crazy I am. Took a spirited 100 mile drive today. Great fun!! Some Idaho twisty roads are made for these cars. Dodging the logging trucks is an extra bonus.

Harvey