M116 Eats Cams???

[Strife]

When I purchased my 380SL at 95K miles, it made a terrible valvetrain noise and I purchased the car with repairing this priced in. As I thought, the rearmost lobe on the RH side was eaten, and the cam follower was severely grooved. This might have had something to do with the oiling tube so loose as to be easy to actually lift off of the cam towers.

I replaced the cam with a new aftermarket cam, and all new rockers. The oiling tubes were cleaned to surgical standards and fitted with new plastic fittings. Naturally, I used break-in lube. To be on the safe side I also replaced the hydraulic compensator for that valve with a new one. The shim looked a bit "polished", but still OK.

All seemed well on the 380SL,for 25K miles.

Before I owned it, this was obviously not an example of a "well-maintained" engine. When I change the oil every 3K miles (religiously), the oil looks old and the car may burn 1 quart every 1-1.5K miles, not great, but not unreasonable at 130K miles. There is some blow-by. My 560SL leaks, not burns, and at 3K oil changes (on a 108K engine), the oil looks almost as good as when it went in.

Anyway, all seemed well on the 380SL.for 25K miles, although there were a few surprises along the way - but nothing from the RH head. Until now. I took the RH side apart, and basically, the same thing happened again, although I obviously caught it much sooner. The cam looks only a little "gouged" on the lobe tip, and the follower is not nearly as bad (but still unacceptable).

I really don't want to replace the cam again. I actually would be willing to do it if I found a good used one (if possible) but I would worry about pushing my luck with the cam tower bolts, which are of course really head bolts.

I have, however, planned on cleaning the oil tube (I do NOT think it is plugged), putting new fittings on, and replacing the rocker. I have the "normal" and next biggest shim size shims that I can install.

Questions:

1. Why does this always seem to happen on the 116? On the RH, and on the last cam lobe???
2. What are the ramifications of putting in the new rocker and the thicker shim? (5.1 to 5.45mm). Any guesses on how long this will last? 10 miles? 100? 1000? 10000? 100000? (ha ha).

Thanks

[tinypanzer]

What kind of oil are you using?

I read in another thread that the older motors used a different cam metallurgy and required zinc additive in the oil, which is being used less and less these days.

But that was on the M103, somebody else will have to tell you if this applies to your car or not.

[Strife]

You know, I've been thinking about this too (ZDDP). I don't know if newer engines have better metal, or if they are designed with lower leverage pressures (there must be a mechanical engineering term for this). It's my understanding that without these additives, it's harder to form a consistent oil film under high pressures. Pushrod engines without roller rockers and early OHC engines are very demanding in this area.

Supposedly, there are additives that contain twice as much ZDDP at the same price as the GM additive, but with 9 quarts of oil to change every 3000 miles, this is going to get expensive if it's needed (+20 an oil change).

[CWW]

You guys with the older motors really ought to be using a higher viscosity synthetic, the film strength is multiples of dino oil, and it doesn't shear down nearly as quickly.

And for peace of mind add a bottle of Ford or GM "Engine Assembly Oil", which has a high enough zinc content to more than offset the new EPA regs' recent reduction in zinc in motor oils.

The old wives' tale about switching to synthetic in a motor that is used to dino oil causing all sorts of oil leaks isn't something I particularly buy into. Yes, it may remove crud that was plugging areas around a bad seal, thus allowing a leak, but that meant the seal really needed to be replaced anyway. So what's the difference. Much better protection for the motor.

[waybomb]

My boat has three big blocks. I still run solid flat tappet cams.

A few years ago, about 15 hours after changing the oil (5 gallons per engine), I wiped all three cams within an hour of each other. So badly that I had to take the lifters out the wrong way in some positions.

Made no sense to me at the time. Lo and behold, I discovered about half of the zddp was removed from my "racing oil" because of EPA regs for catalytic converter fouling caused by zddp.

So now I use Rotella T and a quart of GM EOS in each engine.

Sure would like to find something cheaper than the GM EOS. I bought a few cases of the older stuff on ebay. The stealership wants about 15 bucks a pint for the new stuff.

Someday I'll build the engines with roller cams but then I'll have to change cam profiles, meaning a change in horsepower. And if I do that, I may as well go 1300 hp each with new #6 drives. My wallet won't like that....

[G-Benz]

The "zinc content in the oil" argument sounds compelling, but in Strife's initial post, it seems that the problem is with one cam lobe on the right side, not every lobe on both cams.

I would think excessive wear on one lobe would indicate an isolated problem with that area of the valvetrain, not something a change in oil formulation would cure.

[waybomb]

Agree - since this happened at least twice, I have to wonder if at some point the engine was overheated and resulted in warped items. The head could have been milled flat so it seals.

[Strife]

If someone redid the head, they did a great job EXCEPT on that valve, because the cam towers lined up perfectly and the cam spun perfectly with not even a hint of binding when I reinstalled it (there were no shims under the cam bearings). However, the P.O. really let the "noise" go way too long, to the point where what was left of the cam was banging the gouged-out cam follower to slam the valve down. That could not have done the valve/valve seat/valve guide/springs/etc a world of good.

I'm thinking now of putting in a +1 size shim which MIGHT help nurse this along until I get a complete valve job. That should be big fun. Even if I manage to do this myself it's going to be maybe 500 in tools, 500 in supplies, and 1 for the heads . I assume the worst and will wind up Heilicoiling.

[CWW]

Originally Posted by Strife

If someone redid the head, they did a great job EXCEPT on that valve, because the cam towers lined up perfectly and the cam spun perfectly with not even a hint of binding when I reinstalled it (there were no shims under the cam bearings). However, the P.O. really let the "noise" go way too long, to the point where what was left of the cam was banging the gouged-out cam follower to slam the valve down. That could not have done the valve/valve seat/valve guide/springs/etc a world of good.

I'm thinking now of putting in a +1 size shim which MIGHT help nurse this along until I get a complete valve job. That should be big fun. Even if I manage to do this myself it's going to be maybe 500 in tools, 500 in supplies, and 1 for the heads . I assume the worst and will wind up Heilicoiling.

If you're already looking at $2k for a DIY, you may want to just consider dropping the $4k + R&R labor for a rebuild and be done with the problem for good. I know a great shop here in FL that does fantastic work, and does it all in-house. There must be something similar to you locally.

[waybomb]

Originally Posted by Strife

I assume the worst and will wind up Heilicoiling.

Don't know what you'll be using helicoils on, but if you have room, use a Keensert.

[mercmad6.3]

I have a similar problem with a 380 I picked up last week. Except it's the left hand bank with number 5 cylinder clicking away. This engine also has a suspected cracked piston but that is not a worry yet. The engine has great oil pressure and leak down on a couple of cylinders was less than 5% so it appears to be fine other wise.
I changed the left hand tensioner rail as the existing one was broken in half and the cam was one tooth out ,talk about a close shave!! .

The PO had spent $6000 in 2006 getting a broken chain repaired ...but... who ever did the work didn't bother changing the oil filter. In fact it appears no one has for the last 20 years.
The filter has disintergarted sending bits of fossilied paper through the upper cam oil ways blocking them off. No oil pressure to lifter gallery or the cam spray rail is the result.
It looks as though i will have to either strip the engine ( I really don't have the time) or pull the cam and poke something down the oil ways to clean out the crap.
My left hand cam is worn out though ,so i may just replace it .
BTW the thickest cam pacer is 6 mm so the 5mm is OK.
This is a picture of what the filter looked like when i pulled it on Friday. Some people want their ass kicked.

[Roncallo]

Strife it may be worth while to try to run the engine with the valve cover removed and verify visually that those last two holes are spraying. Also look around the plastic fittings to make sure one of them is not leaking more than the rest. I really think this is an area where MB started to go down hill when they introduced the plastic fittings and chain guides. F$%k it, it will get through warranty.

If the cam spins by hand with lifters out and sprocket removed then everything should be OK unless the cam was put in tight and the rear bearing is now worn. That will cause excessive pressure loss at the rear bearing and starve your rear lifters, so also try to check oil leakage out of the rear cam bearing and compare to the others.

Yes it will be messy and smoke like hell.

Good Luck

[mercmad6.3]

John,Normally you can simply crank the engine( connect the 30 and 50 terminals on the 3 terminal junction box by the battery) with the cover off and the ignition unplugged from the box the oil should /Must pump from the spray rail. If not,there is blockage. This is because the oil flows via the crankcase to the rear of the engine and then up to each head. If the rear most bearing is Not leaking oil from around the cam journal there is a blockage in the block or head.It should also pump freely from the spray rail hole in the rear most cam tower. To rectify this He possibly needs to remove the head and clear out the oilway.
It sounds like he has the same problem as me with bits of filter blocking the oilways.