Roger,

Sean was going to loan me a tool and when i return it to him i can send up one or both old chains from my car. (The 112,000 miles TBF chains) You can maybe pull one of the IWIS chains (OEM Porsche) and stretch them out side to side and take a pic and show just how much stretch there is on a 112K mile timing belt failure chain. Let me know if you want one of the chains for documentation. I think it maybe interesting to some here.

 

Who sells the chain tensioner pads? I can't find them at the dealer.

 

Oh and by the way. I think someone had solved the 16-valve 944/968 chain tensioner failure issue a while back on here in the 944 forum. I believe they said that the way the engine was positioned at a certain angle constituted the repeated maintenance on the cam chain/tensioner assembly. It could be related to gravity and oil pickup.

 

I changed mine on my 944S2 at 100k miles I know many S2 owners that allowed it to go longer and the plastic pad disintegrated and caused catastrophic failure of the came chain. Assuming the 928 uses the same plastic part I wouldn't go more than 100k miles without at least inspecting the pad. The pad gets brittle and crumbles you will be kicking yourself for not changing out an inexpensive part. If your **** the tensioner is about $300 a side but worth the reassurance.

 

I'm in the same boat, having pulled the cover to get some seals replaced...and because I'm a curious bastard who subconsciously must be a glutton for WYIT punishment
I figure I might as well do the pads, no plan to touch the chains, but...

Here's my passenger side opened up. Are the tensioner pad colored links on my chain some kind of master links? There doesn't appear to be a way to remove them but I was a bit dismayed at seeing something other than steel on there...

 

Rob Edwards did a great write up on the chain tensioner pad R&R.

https://rennlist.com/forums/showthre...highlight=pads

 

Top & Bottom pads are $112 a side on the 928 - so $224 for the engine set.
The Germans just put the price up a little 8>(

 

The negative effects of a very weak dollar....

I paid 78 euros for an upper and lower pad for my 944 S2.

 

Ok, Dr Bob is the drive system engineer, I'm just the technician.

So, to check a chain you don't look for stretch in length you look for angular droop. Do this; Take a new chain and an old chain one in each hand. Pinch one link and hold them hanging down. Now, side by side, raise them up near horizontal and compare how much droop the old one has compared to the new one. In some deep dark spec book at Bilstein there is a spec for the amount of droop allowed per link basis.

Next, what wears more, chain or gear? Well, this is a tough answer, but let's use some logic. Given similar hardness, we have exposure to torque. The basic equation is chain links/gear teeth. That is, for one 'revolution' of the chain to get it back where it started there will be links/gear times wear on the teeth. So if we have 10 teeth and 50 links the teeth will wear 5 times faster than similar hardness chain.

Here comes a however; Cams are brittle. I mean they are some of the most brittle compounds around. The lobes are surface hardened beyond that, but the cam gears are very brittle, and I believe they are also surface treated as well as the lobes. One more however; the chains are of course, in motion. Although the cam gears are in motion the gears are just going around happily in a bunch of journals, where the chains are conforming to the gears, and the tensioners. This adds stress to the entire chain when at least half of the gear is unloaded on each revolution(nothing in the teeth, free ride). Yes, I know the loaded and unloaded side of the chain react differently, but there is still stress on the links not in the tension path, that's what the tensioner does.

For these reasons, the chain will wear more than the gear teeth, although there is of course wear on the gear as well. I am replacing the tensioners and the chains on my rebuild because, hey, I'm in there. It seems to me they are a low failure item, but if I had the cam covers off during a TB, I would seriously consider doing the chains and pads. The worst part of the job are the crappy 12pt bolts used on the cam journals. What a POS.

If you do this job, when you start on those journal bolts go slow and even all the way along the journal. Don't get one off completely and leave the other tight, or you can snap a cam, remember - brittle. Don't take the lifters out, and work clean.

 

Very good comments Doc. Why not take lifter out an clean them too while at it using Greg Brown's compressed air dismantling method?

 

You might want to do a search on the 944 forum. Someone located the pads for about $40 each. Mine looked like that on my 944S2 at 106k miles and I replaced the entire tensioner for around $300 to be on the safe side.

Here is the 944S2 as you can see the pad has worn at 106k miles but overall condition was good. No evidence of the plastic getting brittle as i had heard some 944 owners complain about the pad breaking apart at 140k miles on the original pad.

 

Hi Anthony,
Did a search but only came up with the same part numbers I already have.
Top Pad is 928 105 509 01 - I sell for $14.95
Top & Bottom Pad 944 105 509 01 - I sell for $112. Ref was made to buying this part number from Zims for $150.
If you have any further info on where the cheaper bottom pad can be found I woul like to know.
Thanks,
Roger

 

I'm okay with that. Sometimes goo can get lodged in the lifter and cleaning is always good. Replace the lifter in the bore it came out of, and don't use ANY tool to insert it, finger only. If you clean it, might be a good idea to use a little lifer-lube on the cam when installed as you've taken the oil film off the lifter and the lobe.

 

Ok really good points made here in this thread but why cant we grind the top of the pins and cut out a link and add a removable link rather than pull cams.

 

Why would you add a "weak link" into a perfect chain? If you want to check for wear you probably should check the valve time overlap. If the chain wears the valve time overlap should be slightly off.
BTW when I changed my tensioner pads, I only did the pressure side. The fixed side of the tensioner pads showed no wear. This side is barely touched by the chain.