New 380sl owner

spankyway said:

I just traded my old Coleman camper for what I believe to be a pretty decent '85 380sl. I am looking for a good place to possibly buy some engine parts. My car runs and drives but has a lot of miles, 334,xxx, and it smokes. I'm trying to decide if I want to rebuild the engine or replace it. I am also interested in whether or not I can replace the current 3.8 v8 with a larger v8 from a different model MB. Any info would be greatly appreciated.

Click to expand...

I find this very inspirational - that is the highest mileage I've seen on a 116 engine. the PO must have taken very good care of it. I am rebuilding an engine that I believe has ~100K EXCEPT for the holes and bearings, and I hope to get 250-300K before it needs a short block rebuild.

Do you know if it ever had a valve job? Does it smoke all the time or just a lot on start-up?

Unless the car is in INCREDIBLY well maintained condition (and at that mileage, things that you don't think wear out do), I doubt if it is worth a rebuilt engine. It is getting tougher to do, but there are still engine blocks from late 80's/early 90's SEL's with <125K miles that can work, if the oil pans and oil filter pedestals are swapped. The 420SEL has a 380's M116 short block bored out a bit and with a little higher compression. You won't wind up with a performance car out of this, but it will be drivable and a little faster than a 380...

Swapping in a 560 is much more involved because of the control systems involved - people on the W126 forum have done it but actually acquiring a 560SL or SEL is easier...

Generally, when the valve seals on these go bad, the valve guides are not far behind.

Replacing the heads on these engines is not trivial and rebuilding them is not that easy. Even if you pulled them and had the heads done, there are a lot of "while you are in there" parts that can easily add up to (another) high three figures. Most of the rubber and vacuum lines will not survive being disturbed while the heads are removed. Then, there is the issue of helicoiling (actually, timeserting) the block because the screws holding down the heads screw into the raw aluminum in the block. Sometimes, you can get away without it; sometimes, you might be tightening the last bolt, you can't get to torque, and now you have to do the inserts anyway AND you ruined a $60-$90 head gasket. I've done the time-serts with the required jig (which is a fairly rare and expensive tool) and I don't see how anyone could do this while the engine is in the car.

The W126 forum is worth looking at and searching through because they have a lot of hard-core engine guys on there. One guy with a very respected shop trusts only a very small number of machine shops because of longevity issues. Anyone can do a valve job. Far fewer can do a valve job that lasts 150K miles.