valve adjustment mystery

[Joe]

When adjusting the valves on my late 280SL, I found the exhausts were all close to .007", but the intakes were all in excess of .035" (not a typo; this is my largest feeler gauge). The tappet balls would have to be screwed out over a quarter inch, which is not possible, to achieve the desired .003" of lash.
I suspect someone put wrong (too short) valves in the head. The cam doesn't show localized wear.
The tops of the valve springs when the cam points up is about 1.63 to 1.67" above the place on the head on which the valve cover rests.
Any advice is appreciated.
Joe

[Benz Dr.]

Very odd. How far down are the ball studs before you start to do any adjusting? This thing must sound like a pea in a tin cup.

[Joe]

There are no threads showing on the ball studs, so they are near the bottom, right about where the ball studs for the exhaust valves are. No, it didn't seem to rattle, but my hearing is not at all good.
I keep thinking I'm nuts, and wonder why the car ran at all.
With the cam lobe pointing straight up, and the spring off the rocker arm, I am easily able to remove the rocker arm by lifting it off the ball stud, moving it to the side, and then out.
When I turn a ball stud with a 17mm wrench, it is very tight, so I know they didn't creep down because they are too loose.
This is the car that gets 24 mpg on the highway.
Joe

[Joe]

Is it possible the engine has the wrong rocker arms?

[stickandrudderman]

Has somebody omitted the shims?

[Joe]

Good idea, but the shims are there.
I measured the gap between the shim surface and the rocker arm end that is supposed to rub against the shim, and got .199" with the cam lobe pointing upward. Like I said earlier, with the spring off, I can lift the other end completely off the ball stud.
The rocker arms all have "14" embossed on them, both intake and exhaust.
The cam lobes measure about 1.633" for intake and 1.618 for exhaust. The latter figure is questionable, as it is difficult to get onto the lobe with calipers with the oil line in place.
I can't find a number on the end of the camshaft to verify it is correct, and don't want to remove the cam unless absolutely necessary.
This is a puzzler!
Joe

[Joe]

Found the cam number stamped on it between cylinders 5 and 6: 114-051-01-01. The head is number 130-016-08-01.
Thanks,
Joe

[ja17]

Hello Joe,

The shims come in various thicknesses. Maybe you have the thinest ones?  The shim thickness  specs are in the BBB somewhere.

[Joe]

Thanks for chiming in, Joe.
I measured one of the shims to be 4.5mm, which is standard size, and the thickest one offered. My gap, at the shim, is about .199 inch, which is about 5.5mm, so I'd need shims about 9.55mm thick.
I'm coming to the conclusion the wrong intake valves were installed.
If someone happens to have their head off, I'd appreciate knowing the measurement from the valve cover surface to the top of the intake valve spring.

[Benz Dr.]

What happens when you turn the ball stud up to the point that you get .003'' ?

[Joe]

I managed to do that, and had about 3/4" of threads on the ball stud exposed. Does that sound reasonable? None of the threads on the exhaust ball studs show. I didn't put the retaining spring back on, and it will be a stretch for that.
I'm afraid the valve will interfere with the piston, since it descends so much further like this.
Thanks,
Joe

[Benz Dr.]

It's normal and actually a good thing to have some thread showing at the top of the ball stud. There is something very odd going on with your set up. Any chance you can show us a pic?

[w113dude]

does the rocker arm match the other ones?

[garymand]

Nice mistery, the big problem is the geometry.  You are right the angle is extreme.  yes, the thickest shims at 4.5 sounds right, and the cups are only so deep.  Measure the height of your valve head.  We can get a measure of that to compare.  Two measurements maybe, one for the top face to the top of the spring retainer, and one from the retainer top to the rotator top?  What size adjusting wrench do the balls need?  Maybe wrong balls?  New ones are 17mm,  old style is 14mm and I don't know if the deck height is different or if they are interchangeable.  That is a good measurment too, the height of the ball base off the head deck.

No matter what the root issue is, Its hard to imagine someone left the gap so large.  I can imagine someone leaving a .015 to .020 gap, but why leave a uniform .035?  I can't think of anything that would allow the valves to change that much from where they should have been, except someone installing short valve stems, short balls, or thick seats.  hopefully its a ball probelm.  If its valves, we won't know which until you pull the head.  Its not too challenging.  I just r&r'd my head gasket.  one day off 2 days on.  there are only 3 or 4 gotchas to learn.  The late 280sl have the cooling slots between bores.  Mine were in dire need of clearing and with 100K and 40 yers on the old gasket, it was getting soft.  I feel a lot better driving in this 110 degree heat today.  worth the peice of mind.

[stickandrudderman]

Here's a photo of a head that's in queue of parts waiting for attention. It might help.
This is in "as dismantled" condition apart from cleaning so the (worn) ball studs can be seen as they were when the engine was running.





except that my first attempt to publish a dropbox photo has failed.......

[Joe]

I measured the height of closed and open intake and exhaust valves, and they are the same, about 1.87". The ball, before being adjusted by me is also about 1.87" high.
There is "14" embossed on both the exhaust and intake rocker arms.
It takes a 17mm wrench to adjust the ball studs. I put a socket on one, and it was difficult to turn, I'd say around 15-20 foot-pounds.
The shiny part of the cam lobe starts about inline with the center line of the camshaft. Of course, it starts much closer to the circular end on the exhaust valves.
All of the intakes have this big gap. The adjusters and the bases are the same for both intake and exhaust.
I've included a photo showing the adjuster screwed out enough to get the gap at .003.
Its all a misery to me.
Joe

[Benz Dr.]

It does appear to be unusually high but it should still work I would think. Adjusting ther rocker to the required amount should provide the correct amount of lift for the valve to open.


 One thing you can check is the valve to piston clearance. Turn the engine until it's 5 degrees ATDC on number one piston. At this point, the intake valve and piston will be as close to each other as they will ever be. If you have a dial guage hook it up so you can measure how far the valve has to move down before it touches the piston. You are suposed to have about .035 to be safe. I have seen where valves began to hit the pistons once the cylinder head was milled too many times.

Most engines I look at have .050'' or more.

[w113dude]

that rocker arm looks bent upwards,

[Benz Dr.]

It does look bent but I don't think it is. Those rocker arms are very hard material and I can't imagine how one could get bent. However, I once had a distributor with a bent cam lobe shaft. No way you could ever bend one of those so it must have been defective.


Try a different rocker arm and see if it makes any difference.

[garymand]

Joe, take a close look at your rocker arms. 1) i can't imagine how all 6 got bent. 2) all 6 equally?  Pull an exhaust and an intake.  They are the same part and should be identical with similar wear patterns.  Compare them for geometry and wear.  They are high carbon steel forged and hardened, I would expect them to break before bending unless someone went through a lot of trouble to temper them (un-harden them).

But the picture does have the optical impression that the part above the ball is at a different angle than the bar, the top of the bar looks straight while the bottom seems bowed.  Yes, the threads are marvelously tight with about 20lbs of torque is required to rotate them: a wonder of German Machining.  We would use a standard thread and a lock nut.

Your cam lobes look normal.  The rub area is usually not centered on the lobes, which to me isn't normal expected German practice and looks odd on these motors.   This is still very misterious.  I'll bet there is avery simple explanation we are all overlooking.

[Joe]

I think I have solved the mystery, thanks to observations by Shaun and Gary. I pulled a rocker arm off an exhaust valve and compared it to one off an intake valve. The exhaust is embossed with "14" and the intake with "14" and a "4". When I set them side by side, the curvature is quite apparent.
Joe

[garymand]

Wow,  obviously someone named 'The Butcher' put this head back together.  Hopefully some one here can help you with 6 slightly used 14's.  It should have much more pep with correct valve lash. 

[drmb]

Check #1 piston TDC physically and then check the front  timing pointer is corresponding with TDC,also camshaft timing mark is aligned.
I would say the cam timing is out and the intake valves have been hitting the pistons bending the rockers. the intake valves will not bend
as they hit the pistons square on then bending the rocker at the weakest point, ( MB don't make rockers shaped like that )
I have seen this problem over the years on M130 & M114 engines.

[garymand]

Very good point.   My range of rocker knowledge is limited, but the curve doesn't look intented.  It would require the ball adjuster or the valve to be positioned perpndicular to the rocker curve.  Back to Dr. Benz' point of valve clearance at 5 degrees ATDC.  Timing chain slipped or was misfit?

[Joe]

This group is great!
When I installed the Crane kit, I found that when the cam mark was aligned, the timing marks on the crankshaft pulley were on the bottom. This puzzled me, but I read that some of the cars were set up to be timed from the bottom, so I figured it was right.
Now it appears that MBDR has hit a home run. It appears that exactly what he predicted has happened.
I'll rotate the engine until the crankshaft pulley is aligned with the timing mark on the engine, then disconnect the timing chain and rotate the cam until the mark is again aligned.
A compression check seems to be in order after that, to assure the valves still seal ok with new rocker arms. Those pistons must be tough to withstand that force of hitting valves so hard.
It is still astonishing to me that the car ran so well. It will probably run like a scalded dog when I get through.
MBDR, did I see you in "Blokes and Sheds"?
Thanks,
Joe