by Mike C. -
Has your air-cooled engine been a bit noisy lately? Have you had the valve covers off since the last few oil changes? If your answer was yes and no, respectively, then you are probably due a valve adjustment. My experience is to adjust the valves every 5000 to 6000 miles. The reason for the adjustment is this: most air-cooled VW engines up to '81 except for Busses have solid lifters. Without going into the big details, you basically have no oil inside the lifter to cushion the valvetrain motion like you do with hydraulic lifters, so there must be a certain amount of clearance between the pushrod and the rocker arm assembly. For the VW flat four, this clearance is .006" inch. The clearance is set when the engine is cold (less than 120°F) so expansion of the parts is taken into account. Remember, your pushrods are made out of aluminum and aluminum has a higher coefficient of thermal expansion than steel. In short, if you set the valve clearance when the engine is cold, the warmed-up adjustment will be too tight.
Here's what you'll need for the job:
First, make sure the engine is cold. If not, let it sit for a few hours before doing the adjustment. Take
the screwdriver and pry the bail downward off the valve cover. The valve
cover will most likely be stuck on, so you'll have to pry on it a bit.
Careful! Don't pry too hard on the sealing surface of the head or you'll
spring a pesky oil leak. Once you get the valve covers off, go ahead and
clean up the gasket surfaces of both the head and the valve cover to ensure a leak-free
sealing surface. You may want to have an old rag or some paper towels
handy to wipe up the oil on the inside bottom of the head so it won't leak
out everywhere, especially if you have a show engine you are trying to keep clean.
Now, find the spark plug wire that leads from the #1 cylinder to the
#1 terminal on the distributor. Note where that is on the distributor.
Remove the distributor cap and rotate the engine (car out of gear) with the
20mm socket/ratchet until the rotor points to the #1 terminal and the notch
in the crankshaft pulley is lined up with the seam in the case. You are now
ready to adjust both #1 valves. This is where it can get a bit tricky.