85 380SL-Cam Replace (Maybe)? - PeachParts Mercedes-Benz Forum

Strife · #1 11-02-2006, 01:32 AM

I bought an 85 380SL at a good price with a pretty loud engine noise from the right side towards the back, which due to its frequency I was pretty sure involved with the valve train. These engines are supposed to wear out the RH cam faster. The engine has 98K miles. Anyway, I got in there, and the cam is not in great shape, a little scored at the tips of the lobes, but not that bad and not seemingly flattened. I took out a few rockers (and noted where they came from, heh heh) and the one in the back didn't look very good - see attached. I suspect that a mechanic who sees these all the time can deduce what the problem is from wear patterns. None of them looked exactly new (I suspected this problem so I bought two new ones). The new rockers (alright, cam followers) aren't made by MB and the forgings are different, so they aren't exactly comparable. But this one in particular looks noticeably worse. A few questions:

Given the experience of others with this engine, the RH cam is probably in need of replacement, if not now, probably "soon". But is it even worth me replacing the follower alone? (although I also bought a lifter, that is, "hydraulic element", and am going to replace it also.)

This is going to be a "driver". I really should replace both cams, but is replacing just one OK? If I do, naturally I'll replace all the rockers on that side with new.

Some people have posted that non-OEM cams are bad. Any experience? I assume that all "direct replacements" are ground to exact factory as shipped specs. People have been making aftermarket cams for years, so it must be doable.

Reed cams is supposed to be able to refurbish cams (hopefully, to exact specs so I don't have to reshim or anything). Is this worth it - new aftermarket cams seem to go for between 250-400$?

I have the shop manual and am familiar with the procedure for removing the bearings to remove the cam, and how important it is to reassemble properly and to check for binding before actual use. Any gotchas (it's been posted that removing the bearing tower bolts is automatic thread removal on aluminum, but I find this hard to beleive).

I'm doing the timing chain also and although the oil tube was present and installed and functional (all lobes had oil), the plastic fittings just about lifted off of the cam bearings. Hopefully, I'm doing this "just in time".

This is bad, but again I knew of the problem when I bought this and it's been priced in.

How come no manual I've ever seen mentions using "molykote" or breakin lube on this stuff, or even "breaking in" in this area in anymore when parts are changed?

Any thoughts?

mbdoc · #2 11-02-2006, 08:26 AM

I would start with a few new rocker arms...Many times they will last for a long time.

ANY time a cam, rocker arm, or lifter is replaced the base setting of the lifter should be checked & adjusted...

Many aftermarket MB cams are from the SAME billet's as the OE ones from the dealer.

Strife · #3 11-11-2006, 02:46 AM

Upon closer examination, the cam is not just bad, it's incredibly bad. One lobe is actually tapered in the side direction, and there are actual concavities (as opposed to the convex shape of the rocker surface that contacts the cam). A new cam is on its way and I have 8 new (and two darned near new) rockers ready.

The LH cam is very good, though and it's rockers look good also.

Strange, that the LH oil tube felt tight as I removed it, and the RH one just about lifted off.

Is this a strange characteristic of the 116 engine? Any ideas as to why?

Strife · #4 11-11-2006, 02:50 AM

BTW, I contacted Reed Cams and they do not "add metal" to lobes, they grind down the circle. This is not bad (on many engines) but on an MB you would have to get new valve shims, and besides that being a PITA to measure, they are pretty expensive. So, it could be done but with new cams available this isn't financially feasible.