Main.TrailIndexPage | Engine | Valves | Adjusting Valves

Adjusting Valves

This component is part of Engine. For Full Members there is a more extensive section here: Valve Adjustment Tour.

Tools

  • Valve adjusting spanner SW 17 mm
  • 10 mm fork head MB PN # 115 589 00 01 00

Valve adjustment


Normally the head is tightened and the valves are adjusted on these engines at 12,000 mile intervals. Read the procedure for Torqueing the Head.

General Procedure

  • Torque the Head
  • Adjust valves on cold engine.
  • Let engine sit overnight after re-torquing the head.
  • Remove the spark plugs to aid turning engine.
  • Use a new valve cover gasket if yours is stiff and brittle.
  • Adjust via the engine firing order to avoid excess turns of engine…
  • Adjust 1, then 5, then 3, then 6, then 2

Adjustment order


  • The feeler gauge should be a tight slide through, some resistance when sliding through, but not loose. Tighten all the way with feeler in place, then loosen.
  • Exhaust = 0.2 mm or .007-.008 (7 thousandths to 8 thousandths) inches
  • Intake = 0.08 mm or .003 (3 thousandths) inches

You will find that the conversion from metric to US will give you a slightly higher value than .003" and .007". However these are acceptable values especially on a engine with some miles and wear.

Detailed Steps

  1. Remove the valve cover (requires removing the main linkage rod, maybe the power brake vacuum line, breather pipe, etc.).
  2. Turn the engine in the normal direction of rotation (never backwards) until one of the cam lobes is pointed straight up; that's the valve you will adjust.
  3. Determine if it's an exhaust or intake valve and select the appropriate feeler gauge (intake 0.003", exhaust 0.007"). Exhaust valves are on the injection pump side, intake valves are on the intake manifold side. The adjusters are on the opposite sides from the valves.
  4. Try to slide the gauge between the base of the cam lobe and the cam follower (rocker arm). If it goes in easily, too loose. If it won't go in at all, too tight. If it goes in with some effort and you feel some drag when you pull it out, it's good (this may be tough to do with the 0.003 feeler, it's easy to wrinkle it if you try too hard).
  5. If adjustment is necessary, take your valve adjusting tool and turn the adjuster - clockwise to loosen, counter-clockwise to tighten. If your tool won't turn the adjuster, you may have to remove the cam follower and use a deep socket to break the adjuster loose. After that your valve adjuster tool should work.
  6. If the adjuster turns very easily, it won't hold adjustment very long, and you might want to consider replacement.
  7. The easiest way to adjust is to loosen the clearance so the feeler slips in, then tighten the clearance until you feel drag on the feeler. Not so much drag that it's hard to pull out, but enough drag that you can definitely feel it.
  8. After adjusting that valve, write down which valve you just checked/adjusted. I just number them 1-12 from the front. Keep track of each valve so you don't forget one, and double check that you have all 12 listed when you're done.
  9. Then turn the engine until another cam lobe points straight up, this is the valve you adjust next, using the same procedure. You shouldn't have to turn the engine very far. If you observe the cam lobes, you can see which one is coming up next and have an idea of about how far you have to turn the engine. Sometimes two will come up at almost exactly the same time, but one is always slightly ahead of the other. You don't have to be super exact on "straight up", but you want to be close, a good eyeball "straight up" is close enough.
  10. Turning the engine has several options. If you can get a socket on the crank pulley nut, that's one way. For Auto Transmission – put car in Neutral!
  11. If you have a manual transmission, put it in 4th gear, jack up driver-side rear wheel, block the other wheels and release the hand brake, and turn the raised wheel forward while observing the cam sprocket. Strap wrench on the crank pulley may work. "Bump" the engine with the starter. The oh-so-conveniently located camshaft nut must never be used. If you use a tool on the crank pulley, make sure you remove it before trying to start the engine! Taping a reminder to the steering wheel is not a bad idea.
  12. Removing a cam follower requires first removing the little spring that holds the end of the follower, it should just pry off fairly easily. Then push the valve down, and the follower can be lifted off the adjuster ball and pulled out easily. There are special tools available for pushing the valve down. Note on top of the valve is a little cap with a slot in it that the cam follower sits in. The cap just sits there loose, just be aware of it. Don't forget to reinstall the little spring.
  13. If the valve cover can't be removed because of lack of clearance, jacking up the rear of the engine often helps. If this must be done, you might want to loosen (but not remove) the bolt for the rear motor mount (trans mount) to avoid pulling the mount apart.
  14. When all done, reinstall the valve cover. Don't over-tighten the three screws that hold it down or you'll hear horrible noises from the engine when you start it. Screw them in by hand until snug, then maybe another 1/2 to 1 turn.


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