Welding 928 Cylinder block
 

Has anyone out there in the cyber world ever had a requirement to weld the Cylinder block, as a form of repair, on the 928 Engine block. The engine is an M28/42 block, as fitted to a 1989 S4?

It depends where the flaw is and how reachable and cleanable the issue is. For example if it's the bore, not doable, If it's a tab holding on an accessory then it could be do-able. The repair process or the need for replacement will be determined by the details. So post some details or post a pict.

I had the mounting point for the accessories repaired. My local welder did the work. Not pretty, but the engine is back in service.


Before:
https://cimg7.ibsrv.net/gimg/rennlis...7c10e3ec46.jpg

After:
https://cimg6.ibsrv.net/gimg/rennlis...a54d25df96.jpg

Is this the "lowered car used alternator as bump stop" area?

Uh, no this is PO was inebriated, used entire car as bump stop and cassette took one for the team. :-)

i had to do that repair. but thankfully it was just the sleeved "snout" part not the bottom bolts.

Upper block or cradle?

HUGE difference!

Right the roughly 17 % silicon of the alloy used for the actual block (which is part of why it is somewhat brittle) also makes it a challenge to weld. The lower cradle is a more normal aluminum mix.

As the boss says above, I think the lower section is pretty much standard aluminum, while the upper section is hard/brittle silicon impregnated crazy German uber-alloy. So, lower section is a maybe (because warping is a big concern), but upper section much less so.

Alusil can be welded, the puddle just needs to be diluted with a less crack prone alloy by a skilled welder. This is why location matters. Top or bottom of the block is un-important for a competent alu welder however the process does change.

As a matter of practicality... the bore's are not weldable on the friction surface becasue the finished alloy wouldn't be right for a alusil boring process.

Less stressed areas of the block, like gasket surfaces can braised and finished no matter where they are, top or bottom.

It would be great if you would enlighten us with more specifics.....I've had several very skilled aluminum welders attempt to weld the upper crankcase (not on the edges, but in the middle of the valley, from a connecting rod "bulge"),with very poor results. We tired heating the entire block in a special oven, we tried cooling the entire block slowly in the same oven. The problem was not with the weld cracking, but the crack in the block migrating. We tried drilling a hole at the end of the crack, without any improvement.

Welding a 928 cylinder block
 

Thanks heaps to all the responses regarding welding a 928 cylinder block.
I should say, 1 st of all, the welding is required in the centre bearing area of the engine and is in the cylinder block itself. That is the upper section. The alloy used is actually a Reynolds 390 alum that is quite common for use in the Auto industry for construction of engines where the engine is not machined for steel liners and uses steel rings in direct contact with treated aluminium bores.
Some responses have indicated that welding is quite difficult and may not be a viable option. But I would still be interested in finding out if anybody has successfully welded the 928 block. I hope this will shed a little more light on my requirement for forum readers.
Regards

Terry Fitzgerald

Terry, its been done. You just have to find a skilled wellder and hope for good results in the specific area and application. Every area of the block is different in some respect and the heat will move differently depending on the area. Good luck. I think this guy did some extensive welding to the top of the block. Perhaps he can offer some details too.
http://www.928sg.com/block.htm - see block deck 1/2 way down the page.

I am sure it would be appreciated if you would be kind enough to advise what exactly you are trying to repair with some annoted pics - sounds as though you have a TBF'd motor on your hands. Motors subjected to this problem typically have cracking emanating from the spinning thrust bearing. Historically such damage is considered to be beyond repair but there are some pretty smart folks out there in the big wide world and given enough capacity and resource it would be great to learn of how such damage might be recovered.

Whether or not the main casing is specifically Reynolds 390 or something similar I know not but when I looked into the viability of such repair welding consumables in alusil were available on the market so clearly some folks believe the material is weldable. If you can get such repair to work on the 928 block irrespective of the root cause of the damage, it would indeed be most interesting to learn about such from a technical perspective.