TECH TIP - Valve Adjustment

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.

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.

Open up your feeler gage set and fan out to the .006" feeler. Put the gage between the adjusting end (the one with the slotted head on it, towards the top of the engine) and the valve. If you feel some drag but it is not "loose" then you won't have to adjust that valve (lucky you!). But, chances are, it will be loose, so have your 13mm wrench and screwdriver handy. Put your 13mm wrench closed end over the big nut on the rocker arm adjusting end and loosen it. With the wrench still on there, use the screwdriver to turn the adjusting screw until there is some drag on the feeler gage when it is inserted between the valve stem and the rocker arm (told you this could get tricky). With a little patience, anyone can master this technique. It sounds difficult until you actually do it. Leaving the feeler gage in place, hold the adjusting screw where you want it so it won't turn while tightening the nut. Check for some drag with the feeler gage. Remember, there is a fine line between "just right" and too tight or too loose and it doesn't take very much adjustment to find this out. You got both valves on #1 adjusted? Good! Now just turn the engine in the counterclockwise direction to adjust the #2 valves, then the #3 valves, and then the #4 valves, using the distributor rotor and the crank pulley for reference. Follow all the same procedures above for the rest of the adjustments.

When you are ready to put the valve covers back on, just take the new gaskets and slip them in place. The original covers are made to help hold them in, or at least mine were, until you snap them in place. After aligning and positioning the valve cover in place, slide the bail over the cover and snap into place with the screwdriver. Check to make sure the gasket isn't hanging out part way. That's it! You're done until the next 6000 miles.

For those of you running chrome-molly pushrods, you can adjust your valves down to .004" and run a quieter setup. Remember, steel doesn't expand as much as aluminum, so you can run these pushrods under a tighter setting.