Degree of Difficulty: Intermediate
O.K.! So you can change your oil and filter and have mastered changing points and condenser, setting dwell and timing. You'd love to adjust valves but there's some trepidation about removing that valve cover to find out what's beneath it. Believe me, it's no more difficult than what I've mentioned above.
First of all, it's nice to have a new gasket handy, especially if yours has been leaking. They're only a few bucks, so think ahead and get one at the next opportunity.
Here's what you'll need:
- Feeler gauges .006, .007, .008 for a four cylinder and .010", .011", .012" for a six. The 12" long type can be purchased individually (not as a set) from most auto supply houses. Another type which is excellent is the "go-no-go" variety. This one has a step on it, and when the valve is properly adjusted the thicker part of the leaf will not fit. Available from Sears Roebuck, part number 40803.
- A 10-mm Box/combination wrench, a 10-mm 1/4" drive socket and ratchet, 3/8" drive spark plug socket and ratchet.
- A wire or rod .100" in diameter about 3" or 4" long bent 60° to 90° about an inch from the end.
- Some clean rags.
- A wood or plastic wheel chock.
Position the car level or on a slight downhill grade. Chock the front right tire. Release the hand-brake and put the car in fourth gear. The engine should be cold. Remove the engine oil breather hose from the valve cover. (On a six it is necessary to remove the air cleaner housing, easily accomplished with a 17-mm wrench). Remove the domed 10-mm nuts and the bolt at the front of the valve cover. Remember where the various brackets go and don't lose the 6-mm spring washers. The reason we're using a 3/8 drive wrench to do this is so you don't damage the nuts or studs when replacing the valve cover. Put all the hardware safely out of the way. Next, remove the spark plugs. This facilitates a later part of the job.
Carefully lift the cover off, clean and put it safely out of the way N don't drop it or accidentally step on it. Carefully remove the old gasket and dry it between two sheets of newspaper if you plan on re-using same N pitch it if you're going to use a new one.
Now a word of caution N don't drop anything small, and keep it clean. This is not the kind of job to do in a dust or leaf storm.
Most shop manuals give an excessively long procedure on the sequence in which to adjust the valves. It doesn't matter as long as you follow these directions.
What is important is that the valve be absolutely closed when adjusting the rocker arms. You will notice that the camshaft has lobes (bumps as aficionados call them). These are nearly flat on two sides and high round on one side, and low and round on the "backside." When adjusting a rocker arm, it is important that the low round side of the lobe be in contact with the pad of the rocker arm. In other words the high part is pointing away from the rocker and towards the engine. The high part should be pointing directly away from the rocker arm, nearly at 90° so the arm is squarely on the back of the lobe.
To maneuver the camshaft on a standard shift car is simple. You simply place the car in gear and "jockey" it to turn the engine. You can also rotate the fan on 4 cylinder cars and accomplish the same thing. On automatics it is almost mandatory to use a starter button. (See also p. 16, Feb. '77 Roundel).
Pick a valve where the cam lobe is correctly positioned, slip in the .007" (.010" for a six) between the round thing at the top of the valve spring (called a valve spring retainer) and just below the rocker arm where the adjusting nut is located. It should be a sliding fit, not sloppy, not so tight that you must force the gauge back and forth. If it doesn't fit in easily, use the box end of the 10-mm wrench and loosen the nut on the adjuster, place your wire in the hole on the eccentric and rotate it slightly to permit the gauge to slip in. Once this done, try the smaller gauge, it should be loose fit; the largest one should not go in. Tighten the nut with the middle sized gauge still in place and the wire holding the eccentric so as not to permit it to rotate. Then tighten the nut. Be careful not to over-tighten the nut or round it, just good and snug. Re-check your feeler gauge reading as described above. Re-adjust as necessary. The first few will take a while, but you'll get better.
Now proceed to another valve where the cam is correctly positioned. Then rotate the engine so as to position another one for adjustment You can keep track of which ones you've done on a piece of scrap paper or else mark the rocker arm with some chalk. Once you've done all of them, grade your own work to be certain it's right. Remember to chock the wheel each time you've moved the car. After you've checked the clearances again, go back over the adjuster nuts to make certain none were forgotten.
Ready to button up? Fine, now check to make certain that all tools are accounted for and removed from the innards of your patient. Replace the gasket, cover and hardware. Tighten all the hardware with your fingers (that's finger-tight). Now you're ready to tighten the nuts and bolt with your ratchet and 10-mm socket. Start with the upper center nut, next the lower center then the upper one left of center, lower one right of center etc. alternating. This prevents warping the valve cover. The nuts properly torqued are 7-10 ft. Ibs. which is not very tight at all. Over-tightening will gain you a leaky valve cover gasket or else a dome nut without its dome.
Everything clear? Replace the plugs and fire her up and listen to your handiwork. Folks laugh when I pull out my stethoscope and listen to the valves, but just try it you can hear each set and, before long, you'll be able to hear whether you've got one or two that are too tight or too loose. Better too loose than too tight. Well, it took you about an hour and a half, but next time it will go quicker. Did you have fun as well as saving money? We hope so!
Author: Stan Simm and Michel Potheau
Tech. Ed. Note:
Additional optional equipment are a remote starter switch, fender cover, torque wrench, compression gauge. Its always a good idea to torque the head and check compression after adjusting valves.
Also, in this article we've started to introduce you to a "glossary" in order that people become more familiar with automotive parlance. Too many people talk about "erratic" and not eccentric cams, head gasket instead of valve cover gasket etc. I suppose that there really are upper and lower head gaskets . . . However, too many people fill out a repair order at a shop telling the shop to replace head gasket when they meant valve cover gasket. Could be an expensive lesson.
For some time now there have been a few items which I've wanted to pass on to our membership. Many people have asked about how to turn over the engine when adjusting valves On a manual shift car, remove the spark plugs and place the car in fourth gear. Roll it slowly forwards to turn the engine over to the desired cylinder.
When done adjusting the valves, place the car in neutral and then bolt back the valve cover. This will avoid starting the car in gear after replacing the plugs. Also, it is not necessary to replace the valve cover gasket each time the valve cover is removed if it is an original BMW gasket. If it's one of the inferior quality gaskets, replacement may be necessary.
After prolonged use of any BMW or other car, it is unwise to jam on the parking brake. Place the car in gear instead. Applying the emergency brake will warp the brake drums and create a brake "thump" when the car is driven.
The BMW cooling system must have a 30 to 50% mixture of antifreeze in it all year long. Straight water is not an efficient coolant and also encourages rust, premature head gasket failure, and overheating.