Rob Edwards

If your mechanic thinks that's all scoring from the crank, you have bigger problems. What was the end play measure mentioned before the engine came apart?

Mark Anderson

I have yet to see a TBF failure where the webs didn't crack around the thrust bearing

Strosek Ultra

This is a typical thrust bearing failure. The block probably can be repaired. I fixed a similar block a few years back. The main bearings had spun. The thrust bearing web had to be welded and remachined to the correct width. Both the block and the girdle were flycut. I made a special tool to inline bore the mains. One problem was the oil pump not sitting in the middle between the halves. Had to machine the oil pump bore oversize and put a bushing/ring in between the pump housing and the block.
Åke

PHIL928

You do have a valid point, and I have no doubt that someone like you with your experience could repair a TBF engine. But if you ever have the opportunity to come and have a look at what the machine shops look like in the middle east I would highly reccomend it. It's comical, for a better word.

The main business of these shops are industrial diesel engines and occasionally work on cast iron passenger engines. I would imagine that they have maybe never even seen an alusil engine block.

The level of detail required is just not there.

Also, aren't GTS engines more prone to be junkers from a TBF because of the oil vents in the webs which make them even weaker? Just asking, I'm not sure about this.

Strosek Ultra

Phil, I do not know about machine shops in the middle east but assume there
must be somebody being good. I am fortunate to have my own machines but machining can sometime be complicated. Often most of the time is spent making fixtures and/or special tools and getting the object for machining properly set up in the machine. The machining itself usually takes only a fraction of the total time spent. Anyhow I think this is fun to do and when you have finished a difficult job with good results you feel satisfied.
Common sense tells you the GTS web holes make the engine block less strong but are crucial for the bay to bay ventilation as posted here by Tuomo.
The block I fixed was a S4 block not having the web holes. It had a crack at the front main bearing WEB which I had a very good aluminum welder to take care of. This is of course an uncertainty factor but so far it has working good.
Åke

namasgt

Can you also post pictures of the original pistons? Wondering why you were looking for used GTS pistons. There were 3 tolerance group pistons for these engines, group 0, group 1, and group 2. For example if the block is a group 2 size, a group 0 or group 1 piston may be too small for the bore. From what I can see from your pictures the cylinder bores in the block seem to be clean, but it does look like the crank was machining the block. Also since your GTS is a 93 you want to change the connecting rods to the R2 version. I would honestly find a good S4 block with the correct group tolerance for the pistons and install the GTS internals if you really want to keep it a 5.4 liter.
928 International may have a good S4 block in stock.

Hilton

Worse situation is if too-large a tolerance group piston is used - might end up with metal contact.

The point about the R2 rods is well made - there is a factory bulletin saying if the engine ever comes apart, to replace the rods with the revised design.

77tony

Sorry to see this Sheikh and hope you find a solution. T

FredR

Hilton,

Indeed there is- makes me wonder if one has the R1 rods out will Porche give you a set of the R2's to replace them with?

Regards

Fred

Strosek Ultra

Houssam´s mechanic has to measure the piston to cylinder clearance thoroughly. There are three tolerance groups with a 0,01mm step from one to the other. Within a tolerance group the clearance can vary between 0,008 to 0,032mm. However I would very much hesitate to run the smallest clearance within a tolerance group. The nominal clearance is 0,02mm and I would not like to go below that figure. If the smallest piston and largest cylinder (new parts) are put together the clearance will be 0,052mm. For used parts the piston to cylinder clearance can be greater but if it is below 0,06 to 0,07mm it should work alright. The piston to cylinder clearance is not of vital importance, what is most important is the cylinder being all round and straight having no scores and good piston rings. If the cylinder is honed let us say 0,03mm larger in diameter the ring end gap will increase by appr. 0,10mm which to some extent will add to the blow by.
From the picture the piston diameter can be viewed measured at four different points. This is a S4 piston tolerance group 1 (marked on the piston top) and the nominal diameter measured at a point 50mm from the top should be 99,99mm. After 140.000km (87.500 miles) the piston is slightly worn and measure 99,97mm. Note that the diameter vary depending on where the measures are taken. Parallel with the wrist pin below the pin the diameter is 99,38mm. The outside diameter of a piston always taper to compensate for heat expansion and the piston always has an oval shape. Much more prominent for racing pistons. Do remember we are talking very small numbers here, the diameter of a hair is about 0,05mm.
I have a very good set of used connecting rods marked 944.103.110.0R from an early S4. To me these rods looks to be the strongest OEM rods I have seen for the 928.
Åke

GregBBRD

Except you'd need to put $1,500 worth of Mallory in the crank to balance the engine with those heavier connecting rods.

The GTS crank was made to work with the lighter rods.

Strosek Ultra

Well $1500 worth of Mallory will add up to quite some quantity.
http://www.goodson.com/1-inch-Long-T...n-Heavy-Metal/
For balancing a much smarter way is to make things lighter. Quite a lot of weight can be removed from both ends of the OR rod and from the wrist pin. Probably enough to proper balance the GTS crank without adding Mallory.
https://rennlist.com/forums/928-foru...2-500-a-3.html
I got this type of crank balancer in the shop but I have not balanced the above setup so I cannot say for sure. http://www.crankbalancer.com/
Åke

shaikhzeep

Good day all,

Wow i see the thread hot here.Thank you all for these value information.

I been away like 5 days at my work,And i could not get a net.

I will provide all these technical information.

Someone mentioned that 928S4 block same as GTS block? because i have complete S4 engine with similar problem crankshaft machined the block but minimum.

We will see things how it goes.

Thanks

FredR

Do not confuse the original crankcase milling with scoring caused by the crank webs coming into contact with the casing- the latter is much rougher of course.

I am sure our experts will confirm that the original photos you submitted were scored not machined.

The GTS case has some differences - not sure of all of them but as I understand there needs to be more clearance to ensure the rods do not clout the casing and some differences in the way oil drains.

Regards

Fred




Regards

Fred

PHIL928

Keep us updated with the progress!