Setting the valve clearances

[Cees Klumper]

Yesterday, I set the valve clearances. Almost every valve needed some (mostly minor) adjustment; here are two notable lessons learned (at least, for me):

- I tried to remove one of the rocker arms (because I could not get the bal adjuster to move with the Hazet crowfoot wrench) using a handy tool I got from Naj as a gift two years ago (thanks again Naj!). What this tool does is, using the camshaft as a leverage point, depress the valve cap so that the rocker arm can be taken out, exposing the bal stud adjuster completely so that a socket can be used on it. Before, I was using a large screwdriver, which was decidedly low-tech.

In one instance, I just could not depress the valve cap far enough to free the rocker arm. Then it dawned on me why: since the piston will be at its highest point (that's normally where you set the valves), I was pressing the valve down as far as it would go, against the top of the piston, and this particular valve's thrust piece was too thick to let the rocker arm slide free. So moving the crankshaft, lowering the piston, allowed me to easily depress the valve far enough to free the rocker arm, guess-set the valve clearance, and turn the engine all the way back to the right spot, to check the setting. Luckily it was good, or I would have had to go through at least one more full trial-and-error revolution.

- the second thing I noticed was that the middle pedestal that supports the valve cover was bent slightly from the torque-tightening of the head bolts that go through it - enough so that it was touching the adjacent valve cap! I figured this might explain an unusual noise that the engine produced, especialy when cold. Sure enough, after I repositioned the pedestal, the noise dissappeared. Now this phenomenon of the pedestals being twisted has been discussed here before, but in my recollection always as causing them to touch the camshaft, and not a valve (cap). So I was always checking to see whether any of the pedestals were touching the camshaft. After looking more closely last night, actually I can't imagine this could ever happen on at least my M130 engine, because the distance to the camshaft is far greater than to the valve caps.

Anyway, thought I would share this little experience. The whole procedure cost me about two hours (always longer than expected) including retightening the head bolts (first loosen, then retighten to the correct torque), removing and cleaning the spark plugs (all looking very good) and using the old 'turning-the-crankshaft-using-a-27mm-socket-laying-on-the-floor' method. Afterwards, the engine started right up and seems to be running even better than before -but that's probably wishful thinking on my part ...

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[glennard]

Ah Yes, It is a wonderful thing when all is in sync!   Amazing how 0.002 on a valve clearance,  3 degrees on camber, 5 degrees on timing, 6 degrees on cam shaft,  5 degrees on dwell, etc, etc, etc can screw up performance-----  You gotta have rhythm.

[Ben]

quote:Ah Yes, It is a wonderful thing when all is in sync! Amazing how 0.002 on a valve clearance, 3 degrees on camber, 5 degrees on timing, 6 degrees on cam shaft, 5 degrees on dwell, etc, etc, etc can screw up performance----- You gotta have rhythm.

......yeah whoever invented degrees in the first place sure gave us a lot of work to do !!   :mrgreen:

Anyway Cees thanks for posting that. I had read also about the cam touching the r/c cover mounting and could never figure out how ! Never did look to see about it touching the cap. Sure will next time I am in there !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[Kemal]

Boy ! have I got a lot to learn !
You make it sound so easy ...

I put a fresh tank of petrol in today .... :oops:

Kemal
280 SL Manual 69

[jameshoward]

I can't agree more about how seemingly minor changes to valve clearances can make a world of difference. We did mine last weekend. Like Cees, all but one was in need of adjustment - all but one needed to have the gap closed. But only VERY slightly. It ran so much better afterwards - or seemed to.

We discussed head bolts at the time, and I must admit I would offer an alternative view to that of Cees, although I don't have a recently re-built engine and so don't have the confidence that, perhaps, you may have in your engine Cees (assuming you know its history very well, which I don't). Basically, I'd offer a word of warning on the head bolts.  I have learned by a previous experience.  It is not just a matter of slackening the cylinder head and then re-tightening the bolts in the correct sequence and in stages to the correct torque.  The coolant runs in the water jackets between the head and block as does the oil in the galleries.  You are potentially asking for trouble by slackening the bolts then re-tightening them.  Coolant into cylinders etc.
The other potential problem is shearing a bolt.  I have seen sheared head bolts and it could potentially be a nightmare.  Mercedes may recommend renewing the bolts if the head is removed for any reason.  
However, if one has no signs of any leaks from the head gasket, clean oil and coolant, you're best off leaving things alone. i.e  Don't repair something that is not broken.

James

[Cees Klumper]

Thanks James - actually what I do is loosen and then retighten each bolt in turn. So there is never more than one bolt loose. That should prevent any leakages etc.
Because of the rebuilding of my engine, which is a factory replacement block without serial number, I do know the engine inside out, literally. Joe Alexander and I did everything: new pistons, valves, guides, crankshaft bearings, oil pump; the works, except we did not replace the camshaft bearings as they were ok. Also we re-used the head bolts, valve springs and rockers. For me, the engine internals were always a sort of 'final frontier' (Star Trek speak) but no more.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[ja17]

Hello Cees,
Remember to loosen the radiator cap to relieve coolant pressure before beginning the re-torque procedure. The M130, M129, M127 (W113) engines did not have "stretch type" head bolts as later Mercedes engines. Replacement of the head bolts on these W113 engines is usually not required. Modern "stretch type" head bolts (newer cars) actually stretch a specified amount during torquing. The bolts will continue to hold a constant torque even if the head gasket shrinks over the years. The "non stretch type" head bolts (W113 engines) may relax their torque with age as the head gasket changes from years of heat cycles.

I understand James' concern, but I have found head bolts much too loose many times over the years during re-torque. Complications usually arise from leaving them rust into place for twenty or thirty years.

Improvements in modern head gasket materials allow less gasket shrinkage over time, however without the advantage of "stretch type" bolts, re-torquing is still good policy. How often? Every valve adjustment  (12,000 miles).

As Cees mentioned, only loosen then re-torque
one head bolt at a time then continue in proper sequence.

Joe Alexander
Blacklick, Ohio

[jameshoward]

Cees/Joe,

Thanks for both of your recent posts. I echo Kemal - so much to learn; a bit like life in general really.

I will check my bolts the next time I have the cover off using the procedure Cees mentioned. The tip about loosening the radiator cap seems to be a good one.

I am still having problems with low compression and only have one more thing to try before resigning myself to a post about what my options are - hoping to avoid a rebuild!

Thanks again,

James

[Cees Klumper]

Yes Joe - I did loosen the radiator cap before I did anything else, I remembered that one!

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic