Boomerang Baba

Hello,
I have just been to Germany and picked up a complete GTS engine with boxes and all. I am however a little uncertain if this is truly a complete GTS engine or a hybrid GTS and S4...!
The engine no is M28/50 and I know it came from an automatic GTS that had a fire accident in the front. My mechanic is trying to verify whether the tops, cams etc are truly GTS spec or perhaps from an S4...
Does anyone know the exact dimensions of valves? Height, length etc...
We checked the pistons and cylinders and it it is definitely longer stroke than the 5liter cousin. What are the difference between S4 cams and GTS?
Can S4 tops work on a GTS block and pistons?
I hope this engine isn't another white elephant...
I have 3-4 other ailing engines lying around...!
Please advice.
Cheers, Michael

Vilhuer

Valves are exactly same parts.
8 counterweight crank is dead giveaway. Pistons are most likely right also if they come to correct height on TDC.

Different lift and duration. Check xxx xx number stampings at rear end of the cams to verify what they are. Its possible to mix S4, GT and GTS intake and exhaust cams easily into same engine.

Yes, no problems whatsoever.

Vilhuer

Please check this other thread if your engine has late GTS rods and post pictures of them if possible. It would be interesting to know how different they are compared to early style.

https://rennlist.com/forums/928-forum/356382-16-995-93-gts-on-autotrader.html

Check these threads for GTS crank, block and head differences:
https://rennlist.com/forums/928-forum/356751-gts-s4-block-differances.html
https://rennlist.com/forums/928-forum/233242-32v-heads.html

Boomerang Baba

Hello Erkka!
Thanks for your very educated response!
You truly know your stuff!
I will have to study all your links plus the info carefully...!
If it does have some sort of hybrid top, what kind of power are we talking about vs the original 350 horses?
I saw some numbers welded onto the cams, but Autozentrum in Oslo could not track them in their system...
Thanks again and I will see if I can pull out a piston or two later the check the rods!
Cheers, MIchael.

atb

Lose the GTS exhaust cams, they are power killers.

Mike Simard

The workshop manuals have a table that can narrow down the camshaft year and application. Aside from the cast number there's a stamped number on the end face. If you post those we can figure it out.

Boomerang Baba

Hi!
Thanks for your response!
I have some numbers here for you!
On 1 cam it is welded on: 9281052710R
On the other end it is welded: 2089

On the ajacent cam:
9281052730R
On the end it is written: 3141.

Here is the engine no from the block: M28/50AT 81P50616
On the front it is written NB.
On the side of one of the tops:
928.104.4135R
THEN THERE WAS THIS SORT OF STAMP WITH 11 ABOVE AND 87 BELOW ALSO ON THE SIDE OF THE TOP. Is that a date stamp? I checked another 5 liter top i have and there it was 45 above, but still 87 below...
Hope this is helpful!
Thanks again!

SwayBar

Those numbers are for cylinder bank 1 - 4. Are you sure the last character is an 'R'? Or is it a '3'?

If it were a 3, then you have GTS cams for sure. As it stands right now with the 'R' on the end, I cannot make an ID as the shop manuals show the last two characters as digits: 00 or 03, etc.

If you were able to look at the rear face surface of the cams and get those numbers, that would provide a positive ID. The numbers would look like this for GTS cams on bank 1 - 4:

271.03
273.03

M28/50 is a GTS block number.

All specs came from page 15 - 124a of the shop manuals.

Boomerang Baba

Hello,
I just verified that it is indeed 271.03 and 273.03 on the side of the cams. So I have GTS block, pistons and cams but what about the valves. Are they interchangeable with S4 valves? The ones we took out of this GTS engine look and measure up exactely like a S4 valve I have lying around...?
Several of the valve lifters are hard as rock so I guess I need to buy new ones to get this engine pakka. They are abou t80 US or so over here. Any cheaper options? The engine has a fair amount of carbon residue on the piston heads and on the valves. I guess we will just have to bring it back to its orignal glory now that we almost for certain know that it is indeed a GTS engine!
Thanks again for the assistance!

Tails

1990 &1991 European S4 has engine type A M28/42, displacement 4957 ccs. Stroke 78.9 mm and bore 100mm and developes 235kw/320HP with a compression ratio of 10:1

The A M28/50 engine was first fitted to the 1993 Europenan GTS, displacement 5397 ccs, stroke 85.9 and bore of 100mm and developes 257kw/350HP with a compression ratio of 10.4:1

Upper Crankcase Section. Three breather bores have been machined into the upper crankcase section to ensure low resistance air exchange.

Connection between upper and lower crankcase sections. To assemble both crankcase sections hexigon headed bolts are fitted in lieu of studs and nuts.

Cylinder heads. Better cooling was achieved by improved direction of cooling water flow. Additional passages were incorporated on the GTS cylinder heads and cylinder block. New passages are adjacent to the exhaust valve and are located on a transverse centre line between the two exhaust valves and are in axial alignment with the existing passage holes (4 new passages per head). The cylinder head gaskets have extra holes that match up with the new passage ways.

Sump Pan - New baffles fitted to stop oil foaming and the connecting port for the lub oil sender is moved up 5mm.

GTS Piston have a different compression height to the S4 due to the increase in the stroke. (reduced by 12mm. Note there is a specific way to measure this distance as described in the Tech Spec Book).

Forged conecting rods are fitted to the GTS engine which were changed from the cast connecting rods fitted to the S4 with a weight saving of 115 grams.

The crankshaft was revised completely and is fitted with 8 counterweights.

The camshaft cam lifts were changed from 10mm to 9.5 mm for the GTS.
Bank 1-4 are fitted with inlet camshaft part numbers928. 105. 271.03 and exhaust 928.105.273.03. These can be identified by numbers on the rear end surface of 271.03 and 273.03 respectively. (S4 928.105 271.00 inlet and 928.105.273.00 exhaust with identifing numbers on the end surfaces of 271.00 and 273.00 respectively).
Banks 5 - 8 are fitted with inlet camshafts 272.03 and exhaust 274.03 respectively.( S4 272.00 and 274.00 respectively).
S4
Inlet valves open 11 degrees CA after TDC
Inlet closes 35 degrees CA after BDC
Exhaust opens 17 degrees CA before BDC
Exhaust closes 2 degrees CA after TDC

GTS
Inlet opens 13 degrees CA after TDC
Inlet closes 61 degrees CA after BDC
Exhaust opens 28 degrees CA before BDC
Exhaust closes 12 degrees CA before TDC

Camshaft Drive Belt. A new improved Gates belt fitted (reference HSN)

Tooth Belt Cover - The tooth belt cover features a new cut out for visual inspection of belt tension and contidition.

Torsional Vibration Damper - The damper has been adapted to the new crankshaft and was improved.

Filling tower for oil - This was modified to conform to the new crankcase breather arrangement.

I hope this helps you recognise the difference between the GTS A M 28/50 engine and the S4's A M 28/42 engine.

Tails 1990 928 S4 Auto.

SwayBar

Tails, that is one KICK-*** post!

Where did you get all that info? For one, I was not aware of the cylinder head cooling change, nor that the GTS rods are forged versus the sinter-forged S4 rods.

Vilhuer

1992 was first, most common year for GTS.

'92 MY GTS still used studs to mount block lower section. Also pistons and piston rings are different between '92 and '93-95 GTS. '92 includes early '93 US cars which were in reality same as ROW '92 and thus shared same parts.

10mm valve lift is for GT, S4 lift is 9mm.

Boomerang Baba

Hello,
Very educational and professional!
I now have it all spelled out perfectly!
It looks like I do have a genuine GTS engine and that too the improved 93 model year...!
The car it came from was produced in October 1992 and should be a 93 model then.
I guess we just have to get it overhauled then, before we possibly put it into an old 78 with manual trans. Do you guys think that will fit well?
I have all the cables and the boxes from the GTS.
Rock`n Roll!

Jim bailey - 928 International

If you use the existing pistons you need to drill out the oil return holes under the rings. Making all the modifications to run a GTS engine in a 78 chassis is a HUGE task and requires lots of time and money....about all that makes the GTS more powerful than a S-4 is the extra torque from the longer stroke which made it a 5.4 liter instead of a 5 liter.

Boomerang Baba

Hello,
I do have the original pistons in the block. All GTS spec I believe. Do I still have to drill those holes?
Thanks by the way for responding.