Adjusting Valves: The first step in tuning an Air cooled VW
Due to the interaction of all of the engines components, a tune up on a vintage VW must be done in a certain order.
1.Set valve clearances on all valves to spec.
2.Tune the ignition system
3.Tune the carb(s)
VW specified 6000 miles between valve adjustments, but I check them at 3000 miles or less (I like to know what my engines doing).
You should at least have the Robert Bentley manual for your year. This will be your favorite tool while restoring or maintaining your VW. It gives all the correct procedures for doing this and many other jobs on your car.Very basic hand tools are required, and be sure to get valve cover gaskets before you start.
∑.004 and .006 feeler gauge (depending on your year)
∑Short (stubby) flat blade screwdriver.Some aftermarket adjusters/rockers use Allen wrenches instead of slotted.
∑13mm wrench (14mm for 25 and 36hp engines)
∑Valve cover gaskets
Why do valves need adjustment?
When the valves are closed and on their seats: there should be a certain amount of ďslopĒ in the rockers. This is called valve clearance. As an Air Cooled engine heats up to operating temperature, the pushrods expand slightly, thus requiring the need for clearance to ensure the respective valve is fully closed at operating temperature. This is why the valves must be adjusted when the engine is cold!
Your specific clearance requirements should be determined by your year and model (or aftermarket cam manufacturer), by referencing your manual or cam card.
All VWís from 1965 and up call for .006.25 and 36 HP engines get .004, and the 40HP engines originally got .004, but VW changed that to .006 due to burnt valves becoming a problem.
Get er done
Make sure the engine is cold.
To begin, get the car up and safely on jack stands. Remove the rear wheels to easily access the valves. Slide a few rags or paper towels between the bottom of the head and the heater box/header, and something on the ground to catch the drippings (I use a old cookie sheet).
Gently pry the bales off the valve cover on the right side (cylinders 1 and 2). Cover the screwdriver with a rag or use a hardwood dowel if you have nicely painted or chromed valve covers. Pull the cover off the head, and wipe up the oil that oozed out. Keep the rags handy though, it will continue to drip out.
Crawl out from underneath the car, and remove the distributor cap. Around , you will find a groove in the outer distributor rim. This is the mark for #1 cylinder. Get your 22mm, 30mm, or large crescent wrench respectively, and turn the pulley until the notch on the pulley centers with the split in the crankcase. You are now at #1 TDC.
Back under the car, get comfortable, and slide the feeler gauge between the valve stem and the rocker on #1 intake and exhaust valves (front right of the car). If all is as it should be, you should feel a slight resistance while working it back and forth.How tight is a matter of experience. A slight tug is all thatís needed. If you have to use more than your fingertips to pull it out, itís too tight. If it falls out by its own weight, the valve is too loose. Practice makes perfect in this case. If you find the valves tight or loose, back off the adjusting screw lock nut slightly, adjust to spec., and retighten the lock nut.
Get back out from under the car, up to the lower pulley to turn it 180 degrees counterclockwise. This sets you up for #2 cylinder. Check and adjust the valves on that cylinder, and youíre half done!
Go back up and turn the pulley another 180 degrees, remove the left cover and adjust the #3 cylinder, Turn another 180 degrees and adjust #4.
Clean any gasket material off the head and valve cover, and set the valve cover on the head (without a gasket). You are now checking to make sure that itís flat. If yours are warped, think about purchasing new ones. You will most assuredly have leaks. Once both covers check out good, reinstall the new gaskets that you ordered. Some like to use a little adhesive between the cover and gasket, but I install them dry (Less mess!) Reinstall the covers, pry the bails back on, top off the oil, and you have just saved yourself another maintenance bill!
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