Engine rebuild in SF bay area - PeachParts Mercedes-Benz Forum

stukreit · #1 12-14-2013, 06:38 PM

My om617 turbo motor "lightly freshen up" project has turned
into a complete top to bottom job. This engine had been sitting in the corner of a shop for who knows how many years.
The engine number is ground off!! However, the camshaft and cam
towers are the later, higher hp version, which is nice. Also, there's an extra pipe fitting on the oil pan. Trap oxidizer? I probably want to plug it.

Compression was 300's except for 2 in the middle which were about 125. They might have been my mistake, eg neglected the injector seals during test. When we opened it up, nothing seemed particularly out of place,
good head gasket seals, no coolant erosion, no scoring in the bores or on pistons, no broken rings or burned valves. The valves did have quite a ridge on them, and some exhaust valves were more wobbly in their guides
than others.

I have the head completely finished with new exhaust valves&guides.
The machine shop seems a little less certain what to do with the bottom end.

The bores are nicely round but at 90.93 before honing he says its just a hair outside of spec but will work, possibly make some smoke, so he's being very careful to not remove too much material for honing. Pistons
measure 90.86. I'm inclined to stay with this rather than invest in lines/boring/pistons. I want to get this beast put back and in the meantime keep looking for another core in better shape.

Ring gap on old rings appears fine.

The crank and rod bearing shells appear (to me, untrained eye) to be ok,
no noticable wear spots. He sent the crank to a specialist because he doesn't have that machinery. So today he tells me we need "10 under"
bearing shells (he talks in english not metric even though his shop is full of bmw engines!)
and we need the thrust washer in hand in order to measure and finish the crank. I suppose this all means that when they looked at the crank they found it to be not nice enough for a simple polish.
I called peachparts and they can special order if I know exactly what I want, but they kept saying things like
"we haven't sold parts for one of these in 10 years", which means I'm getting zero knowledge with my order, and I don't want to special order
parts with the chance that they are wrong.

So, I'm looking for help in asking the right questions and ordering the parts to reassemble the engine. I have pdf's of the workshop chapters
on sizes and oversizes, and I have the gasket kits for the top end and the lower end/oil pan etc's. Also, will take a recommendation for a machinist in the bay are who might speak more fluent om617.952

I've sent this message to mr Hunter too, because he has made some great
posts in the past, e.g. 274085-om617-952-rebuild-parts-list.html

thanks!

mach4 · #2 12-14-2013, 11:52 PM

The OM617 engines (especially the turbos) are seldom rebuilt. It's just too expensive. The main rebuilder, Metric Motors, charges $8000 for a rebuilt long block. There are so many decent engines floating around, the normal decision is to source a replacement engine from a wrecked car, the junk yard, a rusted hulk with a good engine or some other form of donor source and just replace it. Turbo pistons are not available any longer, so even a rebuild has to be done with used pistons.

The reason you're getting so few responses is that hardly anyone has been through this process, at least in many, many years.

You might want to pause and take stock of where you're at and what it will take to finish the project and compare that to what it would take to just swap in a replacement engine.

I was at two junk yards this week and between the two there were probably 15 (and maybe 20) 617 engines - mostly turbos. A complete diesel engine would run $300 plus core. There is a half price sale coming up the end of the month, so that would bring it down to $150 plus core.

I picked up a spare engine a few months ago for $400 including a transmission. It was complete down to the monovalve. glow relay, down pipe and A/C hoses. The idea is that when my current engine fails I can have a replacement in within a couple of days and be back on the road.

Just a thought.

ROLLGUY · #3 12-15-2013, 12:17 AM

I am in the process of freshening up a 617 (N/A) this week. It is much like yours, in that just a light honing and the bores are still barely in spec. I just had the block cleaned and honed. I will be using the old bearings as well, as they look just like new ones would look. The clean and hone job and the rings only cost $350.00, so all that is left is the gaskets and head bolts (a whole box of parts came the other day from P P for $250). So far about $600 has been spent minus labor and the head rebuild. I am hoping that the head rebuild should be no more than $300. Even if the total labor is a grand, I will have a fresh engine for less than $2,000. I will try to get some photos and post them here, or start a new thread.