Timing the aircooled VW engine

Correct engine timing is crucial for getting top performance and life out of your engine.  For example, if engine timing is retarded too much, you will have a hard time getting it to idle, have pronounced "flat spots" during acceleration as well as never getting the most HP.  On the other hand, if timing is advanced too far, among other things, you'll experience "pre-detonation"; called knocking and pinging which makes your engine run hotter and in turn, can melt pistons and valves.  As you can see, it's important to get it right.

There are two methods of setting the ignition timing on your VW engine, static and dynamic. As you would imagine, static timing is done when the engine is turned off and not running, dynamic timing describes asjusting the settings whilst the engine is running. Lets start off with static timing and go from there..

Static Engine Timing

(How to set timing with the engine turned off.)

    Static timing is setting the engine's ignition timing without the engine actually being run.  This may sound impossible, but I assure you it's easy and very accurate.  This method is an easy way to get a new motor timed prior to starting it for the first time.  Unless you removed the distributor & clamp together as a single unit when the engine was disassembled prior to the rebuild, you really have no other way to get it timed for the initial run-up.  I always do it with new motors and I've never had one fail to start on the first or second try (knock on wood!).  This procedure is also what you do if you're out on a trip away from home and you have to swap your distributor for your back-up.  You DO carry a back-up don't you?? LOL

    If you're timing an engine that's NOT new, warm it fully before doing this.  Those of you with brand new motors, you will probably need to re-check the timing again once your engine goes through it's initial break-in and is warmed.  Warming a motor before setting timing (if you can) is important because thermal expansion, of an engines internal parts, WILL have an effect on timing.  

    Tools you will need to accomplish this will be:

        1.  A 10mm socket & ratchet or a 10mm spanner.

        2.  A simple test light.

    With those simple tools in hand, head out to your VW and follow these 10 simple steps:

1.  Consult your repair manual as to what your engine timing should be set at (ie - TDC, 5 degrees BTDC etc.).  Below are pictured the typical 4 settings for timing a VW engine statically  In order, they are: 7.5 deg. BTDC, 5 deg. BTDC, TDC & 5 deg ATDC.

2.  Hand crank the engine clockwise (CW) so that the #1 piston is in firing position and set it to where your timing should be set for the type of distributor you have.  You will need to align the correct timing mark on the crank pulley with the seam in the case where the two case halves are joined together.  If you accidentally pass the correct timing mark, no worries.  Just turn the engine counter-clockwise (CCW) about 30 degrees and again slowly crank the engine CW until that mark is right in the case-half seam.

3.  Remove the distributor cap and position it out of the way.  Look at where the rotor is pointing.  On the rim of the distributor's metal body (where the distributor cap sits), there is a small mark machined in there.  This indicates where the rotor "should" be pointing when the #1 piston is in firing position.  I say "should" since that really depends on whether the distributor drive  gear was put in correctly when the engine was built.

4.  Loosen the distributor drive clamp bolt.

5. Turn the vehicle's ignition switch to the "ON" position.  DO NOT ENGAGE THE STARTER!!  If you accidentally hit the starter, go back and redo step 2.

6.  Connect the ground wire of your test light to a good ground and touch the positive spike to the spade connector on the ignition points.  The light should be "ON".

7.  Rotate the distributor CW until the light goes out.

8.  Now rotate the distributor CCW very slowly until the light JUST comes on.  Repeat steps 7 & 8 again to ensure you stopped the distributor JUST as the light came on.

9.  Tighten the distributor clamp.

10.  Test your good work by turning the engine 1/4 turn CCW and slowly turning it back CW.  The light should come back on JUST as the degree mark in which you previously had the crank set to gets to the case half.  If it does, your engine is now timed.   If it doesn't, repeat this entire procedure until it does.

Strobe Timing Your Engine

   Once you have determined that your distributor is within specs and functioning properly, then it's time to set the timing.  For using the strobe light method, you will need the following tools:

1.  A 10mm socket w/ extension and ratchet.

2.  A timing strobe light (inductive type shown).

3.  A tach/dwell meter.  

    How I prefer to do it is to set timing while the engine is running with a strobe by the TOTAL ADVANCE METHOD.  By this I mean, you will normally get the greatest HP with more advance.  Here's how I do it:

1.  Connect the tach/dwell meter and timing light.

2.  Disconnect and plug the distributor's vacuum lines if required. 

3.  Loosen the distributor clamp.

4.  Start the vehicle.

 5.  Run the engine up to the point where the distributor's advance mechanisms are at full advance as evidenced by the strobe light.  

6.  Twist the distributor body to set the timing.  I usually set it somewhere between 30 - 32 degrees BTDC (but no more than 32 degrees).

7.  Snug down the distributor clamp, reconnect vacuum lines (if disconnected for timing as specified for your distributor).

8.  Check/set the idle at between 850 - 950 RPMs and take the car for a spin to see how it runs under load.

   If you experience any pre-detonation (pinging), retard your timing a degree or two and test drive it again.  Repeat this until you have good power without pre-detonation.  You can now say your car is timed.

   To save time on future tune-ups, note where the timing is now set at idle and write it down in the margin of your repair manual.  Next time, checking and resetting the timing will be a 2 minute job!!