Mazzini

Dear gentlemen, I have got a 928 S4, my87, my engine is down, i need the bottom part of the engine and the shaft ( sorry for my english); basically the shaft muve 5 mm foward and bit the engine lower part, I'm Unlucky or it is frequently?
second question in Italian 928 Forum everyone look replace the engine with a Chewy a sinn , what do you think about it?

http://www.porschemania.it/discus/me...tml?1280420740

Best regards Lucio

GlenL

Hi Lucio,

What you are describing is called "thrust bearing failure" on this forum. Common enough to have its own name!

Going with a Chevy engine isn't too unusual. Sin? Some people say so.

Seems cheap but will cost more in total than getting a different 928 engine. Hard to say if that's true in your country.

I suggest finding another 928 engine.

danglerb

Pat on the Pelican forum is in Italy and just completed replacing his motor. He may have some tips and contacts useful to you.
http://forums.pelicanparts.com/members/58604.html

Mazzini

The question is, if I rebuild the engine can I have again the same problem, can I hope 160.ooo miles without problem ( with standard maintenance) ?
I scare 928 engine is too "fragile"breakble!

GlenL

Thurst bearing failure is preventable. It is caused by the flex plate clamp creeping forwards on the torque tube shaft. There are two products sold to address it by clamping harder. Then there's annual maintenance to release the clamp, let the shaft slide, and tighten up again.

Once you know about it and take action then it will not happen again.

Please search on "thrust bearing failure" and "TBF" for more information.

Hilton

Lucio,

The failure can be avoided with some regular maintenance.

Read this document for information on the failure, and prevention:

http://members.rennlist.com/v1uhoh/9...earticleTH.pdf

Mazzini

Thank, now I have idea more clear,
I'M looking to rebuild the original engine,
sometime I had think to replace it with a Chewy;
but if the problem is only maintenance i can overcame it,
We'll see.

Some of you know how conversion Work?
I scare give more problem than solution change engine

danglerb

Purists think nothing from the factory should be changed. After trying some changes many see the merit of their point of view. Changes can complicate troubleshooting, and the reasons for the factory doing some things certain ways may not be obvious, so changes can have unintended consequences.

A Chevy swap has two parts, the engine, and the engine brains to control fuel and ignition. The mechanical issues of replacing the Porsche engine with a Chevy are straight forward. The electrical issues are much more complicated, as they must be a hybrid part Porsche and part Chevy. The brains must be programmed to accommodate differences in sensors and load maps.

For anything close to a factory level of performance, the factory engine is a simpler and easier choice. As the desired performance level increases, the lower cost of high performance Chevy parts make it at least as attractive as many other high performance options like boost.

S4ordie

You cannot rebuild and engine that has had thrust bearing failure. At least not without a lot of effort and expense. Much easier to find another used engine and rebuild it.

Landseer

The issue was one of design.
The rennlisters have made inexpensive new supplemental parts to overcome this issue.

Buy a replacement 928 engine.
Buy a special clamp for the driveshaft to prevent the thrust bearing from being self-loaded during driving.
Done.

I've got 3 Chevy V8 engines.
If I could jerk them out and replace them with 928 engines, I'd do it.

In fact, we are contemplating putting a 928 engine into a Jeep Wrangler when its 6 cyl expires.

123

This brings up a few questions. If a Chevy engine is used to replace the original engine in a 928, isn't the 928 torque tube still used? If a basically still stock torque tube is used in the conversion, is movement of the clamp at the flex plate and thrust bearing wear an issue with the Chevy engine? If that is the case, it makes me wonder if thrust bearing failure would be more or less likely with the Chevy engine than with a 928 engine. I guess there probably wouldn't be enough Chevy engine conversions with significant miles on them to have any real data on this if the shaft clamp setup does still get used.

linderpat

A sin? Hell no.....................it's a mortal sin! You will surely burn in forum hell if you do that.
Say 3 hail mary's and get a 928 engine, and this will all be forgotten

Mazzini

Dear friends, I choose to rebuild the engine,
basically because electronic is complicate
to give problem in 928S4 in the standard configuration,
I can't image it in Chewy/Porsche; I'm looking to
upgrade thr flex plate, and to buy a tank with 4 litre gasoline;
at the next failure I promise that i Burn the Porsche...

danglerb

Nothing is wrong with the flex plate, its just the place where symptoms show up. The problem is the front clamp on the torque tube shaft can move, but it tends to only slip in one direction and that creates pressure on the flexplate which eventually wears down the thrust bearing inside the motor. The solution is a better clamp.

Show us pictures of the thrust bearing area in your block, repairing it may not be practical due to damage in the thrust bearing area from either mechanical contact or heat. All of the oil passages would have tiny metal fragments that may prove difficult to completely remove. Usually the block is replaced.

Mazzini

Ill replace the block, but is hard find a new one