Rich9928p

Our fleet of Porsche 928s are aging, and maintenance is necessary to keep our cars running well. Owners of 1987 - 1995 928s and 16 valve 944/968 Porsches need to be aware of cam chain tensioner guide plate replacement as a maintenance item.

Porsche didn't specify a distance or time for changing out the plastic cam guide plate on the chain tensioners. If too much of the plastic material is worn off the tensioner, the cam chain will be loose enough to start contacting the cylinder head cover and the chain will grind into the tensioner mechanism. This is another potential cause of catastrophic failure that could destroy the engine.

My shop, Exotic Motorwerks, recommends a conservative 120,000 miles cam guide plate replacement period. Here are some photos of the service.

The replacement guide plate is flat. The photos of the worn guide plate show that a track under the chain with a depth of about .10 in / 2.5 mm is worn into the plastic. I'd guess that I could have driven another 20,000 or 30,000 miles before too much of the plastic wore away - but who knows how long before the plastic may split in half and completely break apart.

While we were in there, we found that one of the cam galley plugs had come loose and was sitting down in the head. Porsche decided that for 1987 and beyond, the cam shafts didn’t need to be full length (as they previously were), so they just stuck plugs in the holes were the cam ends used to sit. These holes had oil circuits, so if the plugs fall out there is an open hole and oil pressure to that head will drop – potentially causing the cam chain tensioner to have less pressure and enable problems like the chain flopping loose, grinding into the cylinder cover and cam timing become out of spec. The updated solution includes pegs that plug the oil circuits as noted below. This certainly is a while you’re in there upgrade to do.

Inspect the valve lifters and cams for any excessive wear. My 122,000 mile engine was clean and the lifters all looked great - thanks to Mobil 1 synthetic oil.

I have a PDF version of this information available, drop an email note to:
info @electronikrepair.com if you'd like a copy.

Vilhuer

Some early heads have smaller oil hole. Later steel plug doesn't fit in without modifications.

RyanPerrella

yes the tensioner pads should be swapped out if you ever remove the cam covers. $13 each is cheap insurance.

Good point on the galley plugs too

Mrmerlin

make sure to use some loctite 574 anerobic sealant between the cap and head surface before you put the cap back on otherwise there will be leaks to the outside of the cam covers

Glen McCartney

What is the story on the MY85-86 32V tensioner pads? Are they available separately? Does anyone have the part number? I was of the understanding the MY85-86 tensioner pads are different from MY87 and up and are not available, that the tensioner needs to be replaced and that the banjo bolt and or oil tube are different.

This is on my winter to do list, but want to make sure I have the right pieces before I rip into it.

Any information/part number greatly appreciated.

byrdman454

$13 is only one of the pads. To get the other one, the entire kit must be purchased. They were over $100 each not too long ago...

blitz928

Just did that service on my car back in spring. One of my galley plugs had come out out too! Luckily it was lying there. Did the update to the pins, as well as the a new chain tensioners complete. One tensioner was not providing enough tension, so I did them both to be safe. No need to take off the cam covers for awhile now...

RyanPerrella

yes but that pad is under tension, the chain on that side is kept taut by the one cam pulling the other. That pad is really just a bit of a guide and in my experience looks discolored but is not worn anywhere near as much as the pad which is in constant contact with the chain.

ROG100

The top pad is $14.75 currently and the set of bottom & top pads is $112 thanks to Mr. Porsche.
In stock and ready to ship 8>)

As far as I know there are no replacement pads for the 85 to 86 cars.

byrdman454

If you want to trust your engine to 20 year old plastic under multiple heat cycles, go ahead. I would rather have the piece of mind, especially since at least a couple members have found that particular pad with the button sheared off.

Chris

Yep, cheap insurance as it is ugly when the pad lets go .... been there.

Chris

mark kibort

Those are the special chain guide rails on the tensioner pad!

Hey, i cant imagine that being a cause for catastrophic failure. Heck, I was running with missing teeth on my cam sprockets for couple of race seasons.

By the way, how is my old 5 liter running???

mk

Charley B

Rich, the telltale red tint to the oil showing in the oil passage is a dead give away that in fact the superior condition of your engine is due to the use of Amsoil. Thank's for not telling "you know who".

JHowell37

I concur. This is an absolute must.

Rich9928p

It is running strong - still turning heads.