valve adjustment mystery

[drmb]

After changing all of that cam / crank timing you will have to recheck the injection pump timing.
Does your 280 have the two sets of timing marks on the front pulley ?

Lloyd

[stickandrudderman]

I struggle to believe that valves hitting pistons with sufficient force to bend the rockers hasn't caused any other damage. Check everything very closely, including con rods.

[Benz Dr.]

I agree with stick.
 A valve can split a piston in half or make it crack. Not as likely to happen with it hitting the valve due to being one tooth advanced - several teeth out, maybe.

Get some new rocker arms and you should be OK as long as the pistons weren't damaged.

[w113dude]

That rocker arm is from another engine, i have seen them before perhaps on a w114 engine? but not %100 sure.  it seems that who ever did the work the last time must have mixed up a piece from another car, or lost it.

[Benz Dr.]

All in all, nice work, eh?

[Joe]

As for the intake rocker arms being from another engine....
I adjusted one rocker so the valve clearance was the prescribed .003", and then turned the engine over (with a wrench, thankfully). The piston hit the valve and stopped.
It is hard to believe those tough, apparently over-designed rocker arms could be bent without tearing up the pistons, but that is almost certainly what has happened.
I ordered new rocker arms today, and will post what happens.
Joe

[enochbell]

Interesting post, but Joe, there is no way those arms are bent.  They have to be the wrong part.  And they put the geometry so far out of whack that I wouldn't be surprised that, when properly gapped, that they could cause interference.  Maybe someone on the forum can dig up the correct parts?

Greg

[w113dude]

The fact that there is an extra number 4 stamped on it is an indication of a different part. or at least that is my theory. besides the length and the casting of the bent rocker looks a bit longer different.

[Benz Dr.]

I have talked about valve rocker geometry and how important it is to these engines serveral times over the past couple of years. Get it wrong, without even knowing about it, and you will do some quick and serious damage.
I know for a fact that if you run out of adjustment after a rebuild, and the ball stud is right at the base, that rocker angle can wipe out a set of valve guides before you ever get your car out of your shop. The valve guide bore will wear out so fast you won't believe it. The wear will be from side to side unlike normal valve guide wear which is generally uniform in all directions.

Keeping this in mind, maybe it works in the opposite if the ball stud is too high relative to the base unit. I would be pulling your head off for a look because I can't imagine things look all the great after whatever happened.   Good chance the guides were damaged too.

[Joe]

I took off and cleaned all the intake rocker arms. Four are stamped just "14", one is also stamped "3" and the other is also stamped "4".
Looking at the bottom of the arms where the curve would cause the most stress, I observed stress cracks in two of the arms. The arms are apparently not as robust as I suspected.
My plan is to get the car running with new rocker arms and then check the compression and listen for odd noises. If all is ok, then I'll drive it.
Joe

[Joe]

I got my new parts and finally had time to work on the car. I undid the timing chain, set the cam notch on the pointer when the crankshaft pulley "0.0" was on the indicator on top, and reattached the timing chain. Then I reset the injection pump and distributor. When this was done, I started to put in the new rocker arms. First, I screwed the ball adjusters all the way down. Then I put rocker arms on the two intakes that had their cam lobes pointing up. Then I turned the ignition key to rotate the engine a bit so as to put more intake rocker arms on.
The engine jammed on an intake valve. When I examined the timing marks, with the cam lined up, the crankshaft pulley was about 120 degrees clockwise from the indicator!
I backed the engine off by hand and removed the rocker arms. One was noticeably bent, but not much.
When I had the timing chain off, the left side, by the tensioner, slipped from my grasp and fell into the cavity. I fished it out and reattached it. The timing chain feels tight enough to me, but I haven't primed it. I don't think it is loose enough to slip, and the teeth on the cam sprocket still have some flatness on the ends. I would swear everything was aligned when I started on the rocker arms.
Something apparently slipped.
Any ideas?
Joe

[drmb]

Turning the engine with the starter before you have found the cause of the problem is a bad mistake.
Check the front crankshaft bolt and see if it has at least three of the 3mm thick washers under the bolt,check the bolt for tightness if it has been loose or the washers are missing the front crankshaft
woodruff keyway could be flogged out allowing the crank to move independent of the pulley with the timing mark on,so giving a wrong timing mark reading.
If all the keys are in place it is almost impossible for the chain to jump.

[Joe]

Thanks, Lloyd. Now I'm thinking maybe the chain could jump if I turn the engine backwards with a wrench without the tensioner being primed. I'll check the washers on the pulley bolt tomorrow.
Joe

[Benz Dr.]

When I'm working on timing problems I remove all of the spark plugs and turn the engine over by hand. There should never be any tight spots or places where the engine appears to be locking hanging up on something.

If the engine locks up, the cam is likely out of time to the crank. Setting that up isn't too hard to do but you will likely have to move the cam forward or back to get it back into time with the crank. There is really only one place where the cam and crank will run together properly and if it's out by one tooth it will lock up the engine. I would strongly advise you to pull the cylinder head and inspect the pistons for damage. They most certainly will be, but how much is what we don't know, and not knowing could prove to be very costly in the long run. At most you will have a head gasket and some time involved. 

[Joe]

With the crank pulley aligned with the timing mark, the cam indicator was off. The master link on the chain was in the same place, so I knew the chain had slipped on the cam sprocket.
I realigned that, pumped the tensioner until it was tight, and found the chain still has a bit of slack. The chain probably stretched while it was busy bending the rocker arms.
I'll order and install a new chain and new rocker arm to replace the now-bent one.
I put it all together and it started right up!
I drove it around the block and it wouldn't go above about 20 MPH. The car has set for two years, and, while I did drain the fuel tank, there may be deposits in the fuel system. I'll run a can of BG44K through it.
Did a compression test and got 145 to 150 psi on all six. That's at about 6500 feet above sea level. I'll do a leak-down test tomorrow.
The timing is set about 10 degrees after TDC, and anything different makes it run rough. The timing mark doesn't move with increased RPMs. I have an 062 (vacuum retard) distributor and a vacuum advance throttle body. Could the unmoving timing mark be due to this misfit?
I managed to score a VR throttle body which I plan to install, but don't know what to do about the heating hoses (used on the 280 engine to heat the throttle body).
Thanks for observations and advice.
Joe

[Benz Dr.]

Niether throttle body ( VA or VR ) is the right type for the 062.  You need  the constant vacuum type to make it work right with the later 061 and 062 type distributors. If you don't have the all of the switch gear in your engine bay, then use a 051 with a VR throttle body.

[Joe]

Today, I set about putting in valve stem seals. I was able to put those on the intake valves, but was unable to compress the exhaust valves enough to remove the keepers. At TDC for cylinder 1, with the crankshaft mark and the cam indicator aligned, the exhaust valve went down about a half inch before it contacted the piston. Does this seem right? If it is, I need a longer screw for my valve spring removal tool.
Joe

[Benz Dr.]

That's normal because the exhaust valves are so much deeper in the head. I would still take the head off and check stuff out.

[w113dude]

I agree with Dan, it will cost you a new head gasket but you get to see everything out in the open and get to those valve seals too.