Euro SL Camshaft Quirk

[sublettd]

All,

I have been away from this forum for a while, due mainly to being so wrapped up in restoring and rebuilding my '85 500SL.

When we rebuilt the engine (117.962), my mechanic and I replaced everything in the engine except for the crank and 7 pistons. I'd had a busted ring which gouged a small crevice inthe cylinder wall and had to send the block to Renntech down in Miami to get the cylinder bored to the first oversized piston and conditioned.

We put the engine back together with new bearings, timing chain, tensioner, rails, camshaft, rocker arms, towers, etc--and it ran good for the first couple weeks and then it started losing power. Pulled a valve cover off and saw the camshaft was eating rocker arms on the passenger side. Got another camshaft and set of rocker arms from German Auto Parts and installed them. Car still ran like crap for what has been nearly two years now while we have tried to figure this thing out. Also, the passenger side was getting too much fuel, so i drove over and had Larry Felter in Fairhope, AL., at CIS Flowtech calibrate both the fuel distributor and warm-up regulator. All was good there, so we've been stumped.

I finally decided to put the original camshafts back in the car. (I sure am glad I kept them!!!) When we pulled the valve covers the passenger side rocker arms were once again eaten up and the camshaft was pitted and the finish on the lobes practically non-existent. The driver's side was not so bad. There were only two rocker arms eaten and two of the camshaft lobes pitted and the finish gone. No wonder the thing was running like crap, huh?

Well, when I pulled the old camshafts out and laid them down beside the ones that were in the car, there was MARKED difference in the camshafts on each side. More noticeably on the passenger side than on the driver's side.

It seems, though I haven't substantiated, that the camshafts for the 116 and 117 engines are pretty much the same ones. The Mercedes part # as far as we have tracked it shows the same part number for the both the Euro and US versions. However, I can tell you from experience that they are NOT the same camshafts!!!

The lesson learned for me is that when I take a part off of any car I look very closely at the replacement part to make sure it is the same. We didn't do that during the rebuild. We assumed German auto sent us the correct parts. After all, they always had before. Why wouldn't they this time, too? I have paid the price in frustration and aggravation for a long time now.

So, any of you euro owners who are going to rebuild an engine, please keep in mind that the part number for the camshafts is not a good part number. My guess is you'd have to go to a Mercedes dealership who can access the euro parts catalog and order through them at a very dear price.

Also, Mercedes is no longer making the rocker arms for the 117.962 engine. Fortunately, you can buy the correct rocker arms through places like German Auto.

A couple final notes...whenever you pull the head bolts in the aluminum block you may as well go ahead and drill the holes and put Time-Serts in them. You'll pull a thread when reinstalling the bolts and torquing them down. It'll save you at least the cost of a head gasket and some time...

Whenever you replace the rings, the surface contacting the cylinder wall MUST BE CHROMED. Otherwise you'll be eating up the cylinder walls.

This has been a tremendous learning experience for me. Hopefully I'll save someone from making the same mistakes I did along the way.

Regards,

Don