Rennlist - Porsche Discussion Forums

Rennlist - Porsche Discussion Forums (
-   928 Forum (
-   -   Chain Failure Engine. What Next? (

Crumpler 11-22-2018 11:16 AM

Chain Failure Engine. What Next?
Hey gents. Gotta spare engine sitting here for awhile. Curious what I have, but didn't really have time to do an autopsy yet.
I was going to gear up to take it apart this winter. Intent was to salvage block, but the seller left the heads and other components on for me. I believe it came out of an 85, miles unknown.
Known cam chain failure passenger side.
For sure cam teeth gone, chain tensioner assembly wasted, head cracked at tensioner.
What else should I expect? I guessing valves bent.
Is there a remote that I could salvage engine with replacement head and cams and tensioner? Or is it a take what you can get off of it and move along?

Mrmerlin 11-22-2018 11:48 AM

get another head and refurbish the left one,
put it back together update the tensioners if not done already.

928INTL might have some used parts for this hint 1/2 price sale

Crumpler 11-22-2018 02:18 PM

Thanks Stan.
I was hoping that I wasn't just sitting on a glorified coffee table!
I will put up some pics as I go.

Random question for the entire forum: Why two M28 engine numbers? ie., M28 43/44, M28 21/22, M28 41/42 for the S4, etc.
The 86.5 engine I have is a "43" and this one (assuming MY 85) is stamped a "44"
More to the point: was there a difference? Timeline? Location of assembly?

Mrmerlin 11-22-2018 02:31 PM

You should have the 928 book it lists all of the engine codes,
the differences are for manual and auto transmissions,
Also the M28/43 gained 20 HP for the US/Canadian 1986 5 speed models,
due to the Bosch Motronic engine management

Crumpler 11-22-2018 03:18 PM

Got it!
Thanks, never made the connection, as per transmission option. Makes perfect sense.

Wisconsin Joe 11-22-2018 03:54 PM

To expand just a bit, the 'even' 2nd number is the auto version. Odd is manual.

I honestly have no clue on what the difference between an auto & manual engine is.

Mrmerlin 11-22-2018 04:01 PM

flywheel and pilot bearing installation for the 5 speed,
different flywheel for the auto
and vacuum line routing for the auto and deleted for the manual and some other electrical changes

Landseer 11-23-2018 04:56 AM

Miles were just short of 100k. I got it with 70k mi in the original owner platinum car, 85. Car had sat for over a decade. Did a lot of periphial service to get it running right. Struggled through some weeks lean running, warm running, until I figured out several injectors were clogged. Drove it daily for 5 years. Operated the car for about a year with some ticking noise due apparently in retrospect to loose chain. Ran very well otherwise. One day at lunch I started it and the chain failed. It immediately sputtered to a stop and I could hear the tink tink tink of valve's hitting as it did so. There was no reason to spin it again, I knew what happened. The other head should be fine. Figured it was a parts donor, if you reurect it instead be certain to redo the oil pickup and gasket as it was removed for another project. Block and rotational stuff should be fine. It hadn't been opened up until shortly before you saw it, so it didn't sit collecting shop dust for long while open.

Christopher Zach 11-23-2018 08:48 AM

Wow, those pics bring back memories. Yeah I had this happen on my 944S at about 180k miles, same basic results wound up replacing the head over the course of a year, most valves were toast as well. No noise before blowing up.

What concerns me is that the engine had only 100k miles on it? Got a picture of the wrecked tensioner/pad?

Come to think of it, mine blew up on startup as well. Interesting.

Landseer 11-23-2018 10:00 AM

There are pictures in a thread here titled 32 Valve Derailment. I don't know how to post the link from my phone. Davek9, one of the Detroit crew you might have met at frenzy this year, has been advising maintaining the pads on 85/6 due to this tendency. I'm apparently one if the handful of fools that ignored the advice and actually paid the price.

Still a solid block with good possibilities for crumpler. He was in the right place at the right time last year when I had to liquidate.

Crumpler 11-23-2018 10:34 AM

Found the link:

Thanks for the back story Mr. Toft.
I want to thank you again for the awesome pricing as well. :burnout:

At the time, I couldn't believe nobody else had beat me up there. Then things got out of control, moderation not being my strong suit, lol.
Anyway, it occured to me, the S3 engines are not getting easier to find out there. I figured if GB is having a harder time finding them then I should try to save it if I can.
It's also a chance for me to get into one of these and learn something.

Christopher Zach 11-23-2018 11:58 AM

Thanks for the thread pointer. From the pics it looks like the tensioner pad wasn't broken/bad, more the tensioner itself didn't pump up or was very slack with no oil pressure. I'll look up that TSB, but that could do it.

I'll keep my ears open for the ticking sound, I assume it's a bit different than the normal collapsed lifter one (I have a leaky lifter on the 944S, if the car sits for a month the lifters are noisy for a few minutes, then settle down).


Crumpler 11-23-2018 02:31 PM

Ordered a engine stand kit from Arnworks, but I had some time today to get out to the garage and get the head off.
Observations appreciated.
Intake cam seems intact. Can I trust it?
Exhaust side trashed.
Piston faces looked within normal. That white artifact on #2 is paper towel shrapnel.
Head gasket looked pretty good. Original?
Got a close up of the tensioner and broken casting.

Mrmerlin 11-23-2018 06:04 PM

I would not use either of the cams again as the cam without any broken teeth could have gotten stress cracks from the upset ,
maybe the cam could be magnifluxed ,
still better to get another set

Landseer 11-23-2018 07:09 PM

Likely original

All times are GMT -3. The time now is 10:42 PM.

© 2019 MH Sub I, LLC dba Internet Brands