Hi everyone

I try to stay current on our thread discussions so if this has already been debated / opined I apologize, but Cruella has about 150k on her and honestly I hear things on both sides of the fence and would appreciate some guidance on replacing cam chains and pads....I am trying to figure out if I should get ready to do this project this winter or if I've got some time?

deets: early '86. Got S4 tensioners and hybrid oil lines on the way from Mark at 928 Int'l and yes would be letting my shop do the work for the same reason I won't do TB/WP for the first time nor will I allow anyone else to learn on my engine. I am not well off so there are risks I simply won't take.

. We have not had the valve covers off so we don't know their condition but the car was lovingly cared for while with it's previous owner until he had kids and it sat for 8 years but he is an engineer and until then had the cash to get the oil changed every 3k etc. so I am fortunate there that I know it's history. Today it gets Royal Purple 20W50 HPS and some HyperLube, which it loves.

Thoughts / discussion? Thanks everyone in advance.

matt.

 

Did mine couple of months ago - S4 with 130k miles, the wear was very limited on the pads, if just looking at wear I would not have changed, but the plastic was brittle and had some visible stress cracks, so worth doing as preventative measure, I didn't see any reason to do the chains.

 

I also did mine recently, I only changed the pads not the chains. Really the only way to measure chain stretch is to have a new chain side by side with an old one and I am unsure what the acceptable tolerance is.

 

Do you remember approximate mileage when you did it?

matt.

 

Word on the street is that chain failures are very, very uncommon, low revs etc. That being said I have a chain failure engine in my possession.
Even so, the failure on mine was caused by the older chain tensioners and not the chain.

Dave

 

Chains are inexpensive. <$20.

Why not replace when you replace the pads.

 

I changed the pads on both my S4 cars this past spring.
'87 changed at 116.6k
'88 changed at 147.5k

Still running the original chains, I will say I tripled checked the chain tension with the new pads by rotating the engine over by hand several times and they seemed good and of course will increase a bit more with oil pressure.

 

The chains almost never need to be changed because they stretch so little due to being so short. Maybe every 300k miles. You need to remove the cams to swap them, which is a massive PITA.

The pads however should be changed every 20 years/ 120k miles as preventative maintenance or somewhere close to that mileage if you have the cam covers already off.

They are also fairly easy to change. IIRC 4 bolts and they pull right out of the engine.

They are much more common as a failure point on 944s because of the higher revs. But failure is mostly due to the plastic getting brittle due to age.

It's your cars so it's up to you if you want to do a timing belt job to change the chains or just a valve cover job to do the tensioners.

 

Is this recommended by Porsche or just the Rennlist empirically accepted value? Not that I am disagreeing with the general idea of changing the pads, I think it makes sense.

 

The 944s don't particularity rev higher but the vibration and harmonics in the engine are different. If you don't change the pads at latest 120 kkm, you're asking for6 trouble. Must pads fail in the 944 on a cold engine while cranking. Higher valve train inertia combined with no oil pressure are the cause IMHO.

 

No to mention the fact that because of the orientation of the head (near vertical) the cam chain pads aren't submerged in motor oil like they are on the 928...

 

Based on experience with my car I’d say 70K-80K miles is a good point to change pads - wear should be quite apparent by then. My chains had stretched (worn really) noticeably by 185K miles. Probably not close to a failure issue but it was a WYAIT - fix it now thing. YMMV - not clear to me if conditions & driving make much difference to wear here, but 300K may be too long. Evaluate when you change pads (of course it helps if you’ve done a bunch and know where the tensioner should sit with new pads fitted (that’s not me but my mechanic has a good idea). Measuring the chain vs new requires you take it out - by then you might as well change it anyway - all the work is already done.

Alan

 

I just changed the pads on my 240k km 87 and my 26k km 87. If you have the cam covers off just do them regardless of mileage IMO. And the oil galley pins if you have plastic plugs.

 

Yes do the S4 tensioners and replace the pads w/ new.

 

Coming from the 944S world and owning a 944S when the tensioner / pads failed & destroyed the camshafts - I agree that 70-100k miles is reasonable time to do them. Even though they don't seem nearly as prone to fail on a 928, it's not worth the risk.

True story, 1999 living in Madison, WI my 944S had just over 100k on the clock and I wanted to get the chain / pad job done. Made an appointment, dropped off the car and later that day received a call from the service advisor that per their master tech, this wasn't a "job" Porsche had listed as necessary and he didn't understand why it was being done, so it wasn't. I picked up my car and about a year later, it failed. New camshafts ordered from Porsche, put it back together and a year after that it spun a rod bearing. The car has been parked in the corner of my second garage ever since.