Tom DM

Hello Everybody,

Being the proud owner of a fine 95 GTS, I could not get myself to butcher the car for the track.

So I bought a defectif engine (928 S4) on Ebay in order to look into it and eventually put a compressor on it. Electronics should be simplified too. A track dedicated 928 chassis will follow when the engine / compressor works.

I thought the engine was a bit strange: it is a 1987 S4-engine but the timing belt and the waterpump are brand new. Timing is right but the crank (even without spark plugs) was very hard to turn.

Taking away the sump, it is like the crankshaft moved to the front of the engine (to the radiator side) by about 2-3 mm. So the crankjournals grinded the block somewhat, in the sump more copper grindings were found.

My question: is this damage repairable? I suppose the crankshaft has nothing (it being of steel). I will take some pictures and post them sone (in fact when I figure out how to post them).

Greetings to all and regards,


Tom De Moor

Tony

my first impression. The engine is toast and unrepairable.

read this from my web site.
http://members.rennlist.com/v1uhoh/9...earticleTH.pdf

Kevin in Atlanta

Sounds like TBF - Thrust Bearing Failure. Not repairable as far as I know. Do a search for it here.

Garth S

Regrettably, this engine is likely a victim of "Thrust Bearing Failure": This is most often caused by the forward movement of the flexplate in an automatic transmission car, driving the crankshaft forward such that the thrust bearing is consumed. If you are fortunate, only the bearing has failed. If there are aluminium filings present, the block may be destroyed. Hope for the best!! Good luck.

PS - you may wish to persue any assurances given by the seller!

Tom DM

Thanks for the swift replies. It's indeed that kind of damage, Tony, but not as prononced as the picture of the PDF-file

There are no aluminium filings presents, only some copper ones.

The engine is a manual so forward moving due to the flexplate is not possible.

I will check on the Trust Bearing Failure and keep you posted.

Anyway: even if the block is toast, then I will have a nice table

Regards to all,


Tom De Moor

Tony

As bad as it sounds, COPPER is OK..better than aluminum! you need to check the area where the thrust bearing sits. That will be the true test. Perhaps they thought the motor was shot when they saw shavings and felt a wiggle. Perhaps they put the TB and pump on for good measure and decided to unload it.

Be sure of what you have first before you start buy parts to rebuild.

UKKid35

Manuals should not suffer TBF. Perhaps it's a manual engine that was installed in an auto at some time (if it says M28.41) or was originally from an auto whatever the seller claimed (if it says M28.42).

All you need now is an engine from a Cam Belt Failure car and you'll have a going concern (and a few pistons left over).

Vilhuer

Agree, manual engines should not suffer from TBF but on my case there was clear signs of starting problems. Copper was clearly visible in almost all area of rear facing bearing surface. All other surfaces on all five bearings were in much better condition. Engine has M28/49 number and there's no evidence of it ever being in any other car. Can only speculate what caused this. One option is broken pilot bearing. Maybe it created some pressure to crank. It doesn't hurt to check crank endplay on manual cars too.

When looking 928 engine block from below, do not confuse signs of machine work on block sided to TBF problems.





On both above cases there's not any chance of crank having caused those markings. They were made at factory to get rid of excess material in casting. I would expect later engines to need more work than first ones due to wear in casting mould.

Regards,

Erkka

1992 928 GTS 5-speed in need of new bearings
Oak Green Metallic 22L
Classic Gray MX

Garth S

Re. potential of TBF in 5-sp cars,
quote "One option is broken pilot bearing. Maybe it created some pressure to crank. It doesn't hurt to check crank endplay on manual cars too."
Erkka, I think that is a very good observation!

Tom DM

Hello Everybody,

Final update as I finished stripping the block.

Your presumptions were 100% correct: TBF.

The thrust bearing is heavily pitted and has a longitudinal play of about 1mm. At the thrust bearing the vertical face of the crankshaft towards the front of the engine is super smooth, the rear however is motorcross-country.

Guess it is the end of this motorblock and crankshaft.

Anyway: thanks to all for the solid advice.

Tom De Moor

Chris

Bummer Tom, no-one wants to see another block bite the dust ....

Chris

bcdavis

So what is your plan for a track car?

Is it to put an s4 engine, with supercharger, into your GTS, and make it a track car, and sell the GTS engine? Or is the plan to keep the GTS, and make an s4 into a track car, building the engine first? I was a little confused...

It seems like the GTS has so many luxury items, it almost seems like a waste to strip one into a track car. Easier, and cheaper, to strip an s4, and upgrade components like the brakes, to GTS specs, etc...

Tom DM

The plan is indeed to keep the GTS stock and convert a S4 or GT to a trackcar.

For the road the GTS is perfect though I would not say no to 100-150 extra horses. It is indeed a fast luxury car but it misses the eagerness of the NSX.

A lightened S4 or GT with an engine of about 500 HP, decent tires, GTS brakes should be able to upset some people. I like Mark Kibort's approach on this.

I bought the broken S4-engine on Ebay (I knew it was broken) so I could get a good look at its composants. I like what I see and there it is room for improvement.

Regards,

Tom

Bill Ball

Erkka:

Thanks for this note and photos. That's what I saw when I did my oil pan gasket. Scared me at first, but Marc Thomas assured me these were factory machining, as you describe. Whew!!

Bill Ball

I apologize for my ignorance. Could somenone clarify why TBF damage invariably means the block is toast. I would think the damage to the block main bearing holders could be machined and shimmed. I can see the crank machining not being repairable.