Euro SL Camshaft Quirk - PeachParts Mercedes-Benz Forum

sublettd · #1 08-27-2011, 04:57 PM

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

rowdie · #2 08-27-2011, 07:01 PM

A simple look up on the EPC would have saved you a whole lot of trouble. I can find no 116 cam that is the same as the 500SL 117.962. All 500SL are euro. Maybe not all 5.0s.

Strife · #3 08-27-2011, 09:45 PM

Was it "tapping" all the time when you were driving (basically, were the shims correct?).

Were the oil tubes/etc clean?

How is your oil pressure? What kind of oil do you use?

That is a disturbing (and expensive) problem.

It's pretty easy to match a set of cams based on the numbers on the back.

Were those cams are marked 8 and 9 on the back?

sublettd · #4 08-27-2011, 10:58 PM

Rowdie,

Hindsight, as they say, is 20/20. Though I've had a subscription to the EPC site, I've never used it for much. My mechanic has access to the MB site for parts/bulletins, etc., but we never considered going there since German had always been right on the money with their parts. Instead, I have relied on my mechanic. In the future...

Strife,

No outward indication anything was wrong other than it ran like a dog most of the time. I had one cylinder that was a bit noisy after the initial rebuild, but the engine was fairly quiet other than that. As the camshafts ate the rocker arms that increased the distance between the valves and the piston, which--with a zero clearance engine--was a very good thing.

I had to swap a couple shims after measuring the valve height when going back to the OE camshafts. Engine is running very quiet now. No valve noise whatsoever.

The oil tube fittings were replaced when the engine was rebuilt. So it wasn't a problem with the oil. The lobes on the OE camshafts are cut much differently than on the ones we replaced them with. FYI, we went with Mobil-1 after the rebuild, but I went back to my Rotella 15-40 after about 4,000 miles. The engine was using a bit of oil prior to the switch, but didn't use any after going back to Rotella.

I don't recall looking for the 8 or 9 on the new camshafts from German when we replaced them initially, though I do know the OE ones have the 8/9 on them. I looked the OE camshafts over pretty good and didn't see any other part numbers on them--just the 8/9 stamped on the back. Could have missed them, but don't believe so. As I recall, the passenger side camshaft (I believe) is longer than the one on the driver's side. So, it would be pretty hard to mismatch the two. You can bet I made sure I had the correct one on each side before trying to button it back up.

If I were going to go through this again, I'd order the camshaft for the '85 500 SEC/SEL instead of telling the parts guy, "I want a camshaft for an '85 500SL (euro)." Sorta lead him in the direction I wanted to go.

As an interesting aside, I almost had to unbolt a motor mount and raise the engine in order to get the driver's side camshaft out. (The bolt can't be entirely removed because it hits on the brake booster.) Instead, I loosened the bolts and slid the camshaft out of the tower near the firewall. It takes a little finagling to get it back on, but it's much easier to do that than unbolt a motor mount and raise the engine enough to remove the bolt.

Prior to the initial engine rebuild, I had never torn anything much bigger than a coffee pot apart. With my mechanic's help, I tore the engine down and put it back together--including putting in the Time-Serts. It would have been much tougher to do if I had not had the engine manual.

When I went back to the OE camshafts, I did 95% of the work myself--with my mechanic loking in every now and then to make sure I wasn't shooting myself in the foot. Took about 9 hours on the passenger side and about 11 hours on the driver's side. Could have maybe been done quicker, but I was in no big hurry. Just wanted to make sure it was done right.

Thanks for your input and questions. Will be glad to answer any other questions.

Don

alabbasi · #5 08-27-2011, 11:12 PM

I know that the US 420 engine uses the same cams as a Euro 500SL. The part numbers are the same and I've done that swap without any issues on my 84 Euro 500SL.

sublettd · #6 08-27-2011, 11:15 PM

That's good info to know. I'll pass it along to my son, since he will get the car when I'm no longer able to sit up straight in it

Don

Benz Dr. · #7 08-28-2011, 03:23 AM

I've had cases where the part number on the cam shaft was actually a casting number which didn't match anything in a parts book.

The right side cylinder bank is often the one that seems to weat out first with the cam shaft being the biggest problem.

Are you saying you replaced one piston and had that cylinder bored oversize? Not sure how well that works.
I think the cylinders are lapped in with some sort of special slicone paste. I don't think they're chrome plated but the piston rings sure could be.

You were lucky to get all of the inserts installed so the head bolts would fit. Some of them are drilled at a slight angle which is why you need the guide plate. Maybe that's how you did it?

sublettd · #8 08-28-2011, 08:21 AM

Dr Benz,

My mechanic said there was no part # on the camshaft, but I checked anyway. He was the service writer at the local MB dealership for many yrars and really knows his stuff. Good guy!

We did have to bore the one cylinder and put an oversize pison in it. Fortunately the piston came from Benz and had the rings installed. Sent the block to a specialty speed shop in Miami--RennTech--to have it done. And you are correct about the conditioning of the cylinder walls. They did all eight of them. Can't tell any noticeable effects from having one over-size piston in the car. It's running well--now.

The rings were a special order and it was RennTech which told us the outer surface that contacts the cylinder wall had to be chrome. Had ordered rings from German Auto that were NOT chromed and returned them. Benz OE rings were about a thousand bucks. The special order was about $350.00 as I recall.

My mechanic bought the plate and guides--over $600.00--in order to drill and tap the bolt holes. He figured it would be needed again at some point, so was willing to purchase it. The holes are drilled at an angle and I think you would be foolish to tackle that job without the plate. Since I did my block and it came out well, I have since done a second block for my mechanic/friend.

Rebuilding the engine is not cheap, nor is it an easy job. I was fortunate to have a good friend with the smarts and willingness to oversee me while it was done.

Don

rowdie · #9 08-28-2011, 10:22 PM

Guess Al proved me wrong. Still learning. Good luck with the 500SL.

Benz Dr. · #10 08-29-2011, 12:43 AM

Quote:

Originally Posted by sublettd

Dr Benz,

My mechanic said there was no part # on the camshaft, but I checked anyway. He was the service writer at the local MB dealership for many yrars and really knows his stuff. Good guy!

We did have to bore the one cylinder and put an oversize pison in it. Fortunately the piston came from Benz and had the rings installed. Sent the block to a specialty speed shop in Miami--RennTech--to have it done. And you are correct about the conditioning of the cylinder walls. They did all eight of them. Can't tell any noticeable effects from having one over-size piston in the car. It's running well--now.

The rings were a special order and it was RennTech which told us the outer surface that contacts the cylinder wall had to be chrome. Had ordered rings from German Auto that were NOT chromed and returned them. Benz OE rings were about a thousand bucks. The special order was about $350.00 as I recall.

My mechanic bought the plate and guides--over $600.00--in order to drill and tap the bolt holes. He figured it would be needed again at some point, so was willing to purchase it. The holes are drilled at an angle and I think you would be foolish to tackle that job without the plate. Since I did my block and it came out well, I have since done a second block for my mechanic/friend.

Rebuilding the engine is not cheap, nor is it an easy job. I was fortunate to have a good friend with the smarts and willingness to oversee me while it was done.

Don

I've had the heads off a 380Sl but never had he full engine apart. I didn't have any trouble with head bolts but I was fully aware of it. Head had a loose valve guide. The aluminium engines are pretty good because the whole unit heats up in a uniform manner so head gaskets rarely fail. I've done several 450SL's and they're plenty of work but nothing like an old 300 SE. That's a very hard engine to work on.

Sounds like you did it right with the guide plate and everything. I have a machine shop do all of that for me. I find the parts, take it apart, and put it back together.

sublettd · #11 08-29-2011, 08:29 AM

Benz Dr,

The engine had 147,000 on it when it was rebuilt and the driver's side headgasket did have a slight leak.

If I can figure out how to post pictures to this site, I'll take a couple shots of the worse rocker arms and camshaft lobes and put them here. It's pretty remarkable to see just how eaten up they are. We're going to send the camshafts and rocker arms back to German and insist they give a refund. Not sure how successful we will be, but I know there won't be a refund if I don't try to get one.

If I recall correctly, the 450SL block is iron and much less prone to some of the problems often encountered with the aluminum block.

Another tip for anyone who removes a head bolt on the aluminum block is to "pop" it loose. By that I mean put a fair amount of torque on the wrench and then "lunge" into it and snap the bolt loose. If you gradually apply pressure the bolt will loosen, but along with loosening the bolt you are also very likely loosening the threads in the hole. I had one thread still wrapped totally around the threads of the bolt when it was removed. I keep it on my dash as a reminder.

The more I work on these cars, the more I see how your shadetree mechanics can really screw one up. Plus, there are a lot of specialty tools involved. Fortunately, my friend has all of them and gives me access to anything he has when I need it.

Here's another nice job. If your trunk lid fails to lift when you punch the button, one or both of the torsion bars is broken. Replacing the torsion bar requres a special tool. When we ordered ours, we left only one more remaining in the world. It requires almost superhuman strength to bend the torsion bar into position and place it in the notch. Monstrous job for something that would seem to be so simple.

I've learned a lot about the 500SL and its engine. Probably don't know as much as I think I do, but I now have a lot more respect for my local Benz mechanic than I did.

Don

bwostosh · #12 08-29-2011, 09:52 AM

What a story, I would have4 cried seeing a chewed up camshaft. thinking, where did those metal particles go.

I am rebuilding an iron block 300SEL 4.5 motor and impressed at the nice internal condition of the original parts.

sublettd · #13 08-29-2011, 10:01 AM

We were pulling our hair out trying to figure out why the camshafts and rocker arms were being eaten up in the first place. Never saw any metal shavings on the upper part of the engine, so figured the shavings were winding up in the oil filter. Never tore a filter apart to see what the shavings looked like, but have seen shavings from other engines in the filter.

Good luck with your rebuild. You'll have a story to tell.

Don

Benz Dr. · #14 08-29-2011, 03:18 PM

It could be the oil you're using. Most modern oils don't have any zinc additive and on flat tappet cams like this engine you can have some pretty heavy wear. I know Royal Purple has this additive but I'm not so sure about other oils. I tend to use oils recomended for diesels as they seem to have better anti wear packages.

sublettd · #15 08-29-2011, 04:37 PM

Benz Dr,

I ran Shell rotella 15-40 in it prior to the engine rebuild and everything was in pretty good condition when we tore the engine down. And, as mentioned above, I went back to Rotella about 4,000 miles after the rebuild. Believe this is a pretty clear case of installing the wrong camshafts.

Don