blown 87

Progress pics and a mystery part.

I finally got going again on my 928S4, made some progress this week.

Got the body done except for wiring the GTS mirrors, (the GTS mirror gaskets are a bitch) the inner door panels and the fuel filler door.

I got the short block striped today, so the block can go to the machine shop for decking for the Cometic head gaskets.



We found this mystery part on the floor after turning the motor over, I do not have a clue where it goes or what it came off of, not even sure if it goes on a 928, but it was right under the engine stand.

Mystery part next to the finished heads.



Next to a 8MM wrench.



Any ideas?

Greg Nettles

Mrmerlin

since you have the head make sure to inspect the anti syphon check valves for the ball seat to be fitted tightly into the head.
If its loose remove it and clean the port then install it with some Green Locktite and stake it into the head
If its loose it can be pushed upwards and block off the oil passageway to the cams and lifters, this will result in a seized cam .
Also flush out the oil galleries before installing the heads, and fit a new O ring to the check valve plug
That bronze disc doesnt look familiar

blown 87

I got new springs, o-rings and the ***** for the check valves, I tried to get the seats out before I sent the heads out, they were tight.
I will check them again.

We also got the crank scrapper and windage tray fitted.

All of the bearings looked great, most had 80-90% of the dull gray babbit left on them.

The only problem spot I saw was on the rear face of the thrust bearing, even though it was still in spec, it was down to the copper color, so I guess I made a good call to pull the bottom end down.

I would not put it past one of my guys to have just put that mystery part there to, shall we "Confuse" me.

Nobody would admit it today, so I am not real sure where it came from.

They are picking it up Monday to finish the machine work, I should have almost all the parts.

I am going to take Greg B's advice and get factory Porsche rod bearings for it, I had bought a set of the aftermarket ones, live and learn.

BC

Greg is downright **** on *** correct on those Porsche rod bearings. Serious differences in clearances.

blown 87

My guess is that Greg B is correct on most things 928.

I was really surprised that the little amount of wear the bearings had on them.
The bore wear was not measurable with my bore gauge.
(try that with a small block Chevy)

One thing I did not expect to find was that the oil control rings on three of the pistons were very gummed up and one was out right stuck, but every thing else on the pistons looked great, no scuffing to speak of.

The sticking oil control rings has to be oil related.

On a side note, I talked to Mike Grubber this week, he has been the Valvoline NHRA racing rep for 25 years, he knows motor oils.

I worked with Mike for years at Valvoline and he told me since the change to api spec SM that mobil one has the worst additive pack that you can find in a name brand motor oil right now.

This one came as a surprise to me, he is now recommending Valvoline synthetic Racing oil for me to use, like I said, Mike is a friend, he knows oil and this was not a sales pitch.

He also said do not use any brand of API spec SM oils in any car that does not have a roller cam.

Any way, no SM oils for me, just SL oils even in my roller cam engines.

BC

All the engines I have disassembled have had pretty bad oil rings as well.

blown 87

Considering how pristine the rest of the inside of the motor was, other than the thrust bearing, I was not expecting to see a problem with the oil control rings.

It sure looked to me like some of the other oil related things I have seen, but usually I have seen them on the second compression ring in the past.

Interesting that you have seen this before, how bad are the ones you have seen?
So stuck they could not be moved with out a lot of force?

BC

I very well running 89 S4 motor I took apart had some rings STUCK, seriously - at 75k. An 86 motor had a few that were VERY tight (200,000 miles)

A couple 2V motors had some impacted rings as well.

I will say that the evidence on this most recent 2V I rebuilt says that they WERE stuck, but repeated usage of redline motor oil seemed to have loosened them alot.

blown 87

The motor oil issue IMHO is just another instance of the federal government sticking its big ugly nose where it does not belong.

I mean really, taking the anti wear additive out of a motor oil because it MAY contribute to increasing the rate of degradation of a catalytic converter substrate in SOME engines that have enough miles on them to use a certian amount of oil.
I want to thank all the environmental fanatics for protecting me form myself.

Do you have any info on what kind and grade of oil these motors were running and the change interval?

After talking to Mike, I feel fairly confident that my stuck oil control rings were the result from the oil that had been run in the car, and my use of mobil one did not help any.

I can tell you from my time working with motor oil, the additive packs can do some weird stuff, just a simple change from a 10-30 to a 10-40 by adjusting the amount of the base stocks can cause problems with rings and some additive packs.

BC

The one that had redline was 20-50. The others could have been all sorts.

I will also say that the AMSOIL that I ran in the 89 motor for 40,000 miles before I took it apart DID NOT HELP the oil control ring impacting into the piston and staying there. I have not used Amsoil since.

I will probably stick with 20/50 or maybe a bit thinner Redline, or something like the HD oils.

Rob Edwards

I'm cleaning permatex gasket goo from my oilpan and I look over and I see this:





Is it possible this is your mystery part? Mine is exactly 8.00 mm in diameter. When I changed the OPG on my '90, I recall the oil level float thing falling off when I turned the pan over- perhaps these little bronze disks are not reliably attached and fall off?

Just a thought, not sure if it's the same thing.

blown 87

Rob, that is a good idea, but my reed switch is ok.

I had taken the oil pan off a while back and was not near the engine, but I did take the switch off and the plate after I striped the block, so I am going to go recheck it today after my short nap.

Maybe I was looking right at it and did not see something.