M117.986 rebuild, and parts availability - any observations?

[ptashek]

As the title says, this is something I'm looking into.
My M117 (euro M117.986) has barely passed 75k miles from new, but I want to rebuild it completely at some point in the future, while gathering parts along the way to spread the cost. Unfortunately my resto budget didn't allow for doing it as part of that job.

Did any of you fine people tackle this from a parts perspective in recent times?
How does it look in terms of availability?

[UTn_boy]

The only thing that I can see being a problem are pistons and rings availability.  DEVES sells rings that are of acceptable quality, and there are companies world wide that you can send a piston to that they can duplicate exactly, so not all is lost there.  Everything is else is pretty much available new, including one of the camshafts if needed.  I believe the crankshaft isn't available, but if the ones(s) you have are only worn, then the journals can be machined down to accept undersized main and rod bearings.  Obviously, this will be a costly adventure, but worth it.  And here again, aftermarket parts aren't recommended.  We already know aftermarket parts are always of lesser quality to some degree, and that's the last place I'd want an aftermarket part.... in inside of my engine or transmission.  That's my opinion, though, and is based upon years of observations.  So take that as you will. 

[s class]

Rebuilding a 3.5 or 4.5 properly ends up being pretty expensive.  The most important thing is to build up a relationship with a really competent machining shop.  Whilst the quality of parts is a worthy topic of discussion, the final outcome will be more heavily influenced by the accuracy of the machining.  For example, can the machine shop :
- bore and hone the block such that the bore taper and ovality is better than 0.01mm?
- machine for individual piston clearances?
- machine the cylinder head parting surfaces whilst reducing the thickness of the heads by only 0.1mm, and maintaining perfect camshaft pedestal alignment?
- change valve guides correctly, with correct insertion depth and proper reaming for correct valve guide clearances matched to individual valves?

THere are lots of machine shops that claim to be able to do this type of work to standard, but sadly, my experiences here in South Africa are that very few really can. 

[marku]

It really depends on how far you want to go and of course the current state of the engine and who is going to do the work. I did my 450 myself and it was a struggle at times as I started with no knowledge or information on the engine. As to the actual cost to me I am not sure because, although I could look it up as I have all the invoices, work that was put out was specific and just a single item each time. I decided what I wanted to do and then started buying parts individually long before they were actually needed and all were new from 'Classic Partner' Mercedes-Benz of Poole who were very helpful as I found my way through the project. Because the cost was spread out over quite some time I was not generally aware of the overall cost and therefore managed to delude myself that it wasn't significant. Obviously if you are going to have someone else do the work not only will it be expensive but the cost will be very apparent. However doing it myself was a very worthwhile project by acquiring information relevant to the engine, from many sources, and of course doing the work.

[ptashek]

Thanks everyone for the pointers. Definitely lots to consider here. I'd love to do this myself, but it'd probably take years with the amount of free time I've got. Better left to someone who knows what they're doing

I've briefly checked EPC and prices yesterday and so far the bill for everything new (including heads) that's still available, is about 7k EUR gross. I'd say it'll be tough to fit a full rebuild in under 10k with labour?

What's bizarre is that you can still get connecting rods, but not pistons. Exhaust valves, but not intake. Just one camshaft, left one I believe. Cam tower bearings, but not the towers themselves...