How to........set your timing - Part 1

Discussion in 'How To' started by b0dyr0ck2006, Aug 27, 2011.

  1. Set the Timing.

    IMPORTANT NOTE: It is important to understand the four-stroke design of the air-cooled Volkswagen engine (intake, compression, combustion and exhaust), both when adjusting the valves and setting the ignition timing. As you turn the crankshaft through its complete four-stroke cycle you will note that you turn the alternator pulley around TWICE. You will encounter TDC at Cylinder #1 and again at Cylinder #3. To time the spark properly, you MUST make sure that it is Cylinder #1 at TDC and not Cylinder #3 (voice of experience!). If you are at all unsure, follow the Finding Top Dead Centre procedure below.

    Note: This procedure gives the timing specifications for both the vacuum-advance (single and dual) and centrifugal-advance (009) distributors, as all three are used with the 34PICT/3 carburettor. The timing is correct (at idle) when the spark leaves the distributor exactly when the correct timing mark on the crankshaft pulley lines up with the crack in the crankcase.

    Preliminary Settings -
    First make sure the valves, the point gap and the idle are properly set. Changes in point gap and idle speed change the timing.

    Find Top Dead Centre (TDC)
    -
    If you are uncertain as to which mark is which on the crankshaft pulley, determine TDC as follows:
    Remove the #1 spark plug.
    Note: The #1 cylinder is on the right side, closest to the front of the bus.

    Remove the distributor cap and find the small notch on the rim of the distributor body that marks the position of the #1 spark plug wire (5 o'clock for SVDA distributors; 7 o'clock for 009 distributors).

    Note: This is a very thin little notch in the metal - it's easiest to find if you run your fingernail around the rim of the distributor body.


    With a 19mm socket or 19mm box-end wrench (ring spanner) on the alternator nut, rotate the engine (clockwise -- the way it goes) until the rotor is approaching the #1 spark plug position (the notch you found in the rim of the distributor). This will place the piston near the top of its stroke.

    Insert a pencil (eraser end first) into the #1 spark plug hole until it rests on the top of the piston.

    Note: Make sure that the pencil is horizontal, not crosswise of the cylinder. If you're not careful, you make break off the end of the pencil, which will then fall down into the cylinder! Not good!


    With the 19mm wrench (spanner) on the alternator nut, and while holding the pencil on the top of the piston, move the crankshaft back and forth across the #1 spark plug position until you find the point at which the piston is highest in the cylinder (i.e., the pencil is at its furthest point out of the spark plug hole). This is Top Dead Centre.

    Note: It is important to get the piston roughly at TDC (TDC mark near the split in the crankcase -- Step c. above). Then place the pencil in the hole and rock the piston back and forth to find the centre of the no-movement position. If you put the pencil in with the piston at or near BOTTOM of its stroke, and place it so that it is sitting at an angle across the cylinder (the spark plug hole is on the upper side of the head), then rotate the crankshaft, the piston may push the pencil sideways break off the end. Removal of this end bit of the pencil is expensive!

    On the crankshaft pulley, with piston #1 at TDC, make a mark (with white paint) exactly opposite the split in the crankcase. This will be your TDC mark and the starting point for other timing marks you will make. You will find the timing mark(s) that apply to your configuration by carefully measuring from the TDC point around the rim of the crankshaft pulley.

    While you're at it, rotate the pulley 180 degrees and paint a mark on the pulley there. You will use this point when you adjust the valves (this is the point at which pistons in cylinders #2 and #4 are at TDC).

    ~~~

    Make Your Timing Marks -

    The distances around the pulley (arc distances) for the various timing marks are calculated using the following formula -

    Arc distance = 2(pi)(r)(alpha)/360

    Where -

    Pi = 3.1416

    r = the radius of the pulley (in mm)

    Alpha = degrees of the appropriate arc

    (e.g., the appropriate timing advance).


    The arc distances that follow are based on a pulley diameter of 175mm, thus a radius of 87.5mm. Be sure to measure the diameter of your pulley and use the radius of your pulley in the following calculations.

    Timing the Various Distributors -

    Note: The double-vacuum advance distributor must be timed with the engine idling, using a strobe timing light. The 009 and single-vacuum distributors CAN be statically timed at 7.5o BTDC, but timing with a strobe light is recommended. If an electronic ignition system like Compu-Fire or Pertronix has been installed, the distributor MUST be timed with a strobe light.

    Vacuum-advance only distributors: From 1961 to 1971, Type 1 distributors were vacuum-advance only -- they had no centrifugal advance. These distributors are timed at 7.5o BTDC; this point is found by measuring on the rim of the crankshaft pulley 11.5 mm to the right of the TDC notch.

    Dual-advance distributors: From the TDC mark, measure on the rim of the pulley 7.6 mm to the left from the TDC notch and mark with white paint; this is 5o ATDC, the point at which the dual vacuum advance distributor is timed.

    009 and SVDA distributors: Measure on the rim of the crankcase pulley 11.5 mm to the right of the TDC notch. This is 7.5o BTDC; mark this point with white paint. This is the point at which the centrifugal advance (009) and single-vacuum dual-advance (SVDA) distributors are preliminarily timed (the maximum advance at 3500 rpm will be the final timing point for these distributors).

    Maximum advance: From the TDC mark, measure on the rim of the crankcase pulley 46 mm (for a 175 mm diameter pulley) to the right of the TDC notch. This is 30o BTDC; mark this point also with white paint. This is the maximum advance point at 3500 rpm, the timing point for 009 and SVDA distributors.

    Timing with Stroboscopic Timing Light
    -

    Note: Timing with a stroboscopic timing light must be done with the engine warm. If your timing is so out of whack that the engine will not start, the SVDA and 009 distributors can be timed statically to get you in the ballpark. See the Static Timing procedure below.

    Stroboscopic Timing Light


    The strobe light emits a very bright light which is flashed from a pistol-like instrument when the #1 spark plug fires. Be sure to read the instructions that come with the strobe light.

    Setting the 009 Centrifugal Advance, Single-Vacuum Dual Advance (SVDA) and Vacuum-Only Distributors with a Strobe -

    Note: The approximate idle timing setting for the centrifugal advance distributor (009), the single-vacuum distributor, and the vacuum-advance only distributor, is 7.5o Before Top Dead Centre (BTDC). This means that as you view the 7.5omark at the crankcase split (with the strobe), the TDC mark on the pulley will be about 11.5mm to the LEFT of the crankcase split when the distributor is properly timed. Again, this is the APPROXIMATE timing setting at idle.


    Important Note regarding vacuum lines: When timing the vacuum-only distributor, the vacuum line(s) must be attached. The vacuum line on the single-vacuum dual advance (SVDA) distributors must be removed from the vacuum canister on the distributor and plugged to prevent air from being sucked into the carburettor during timing. For BOTH the centrifugal-advance (009) and SVDA distributors -- ifthere is a vacuum hose running from a port in the intake manifold under the carburettor up to the air cleaner, this hose must be removed and plugged as well, for the same reason. Be sure to plug it such that air will not be sucked into the intake manifold.

    Summary regarding vacuum hoses during timing: Just make sure the vacuum ports on both the carburettor and the intake manifold are PLUGGED so air won't be sucked in during timing.

    For these distributors, the advance timing is more important than the idle timing. Ideally it should be 28-30o advanced at 3500 rpm, and then should return to something close to 7.5o BTDC at idle (900 rpm). The centrifugal-advance portions of these distributors vary -- if the maximum advance is set to the correct 28-30o BTDC at 3500 rpm, an idle timing in the range of 5-8o BTDC should result.

    Set the handbrake firmly and block the wheels. Put the gearstick in neutral.

    Make sure that the maximum advance timing mark (as determined above) is clearly visible on the crankshaft pulley (i.e., marked with white paint).

    Attach the inductive pick-up clip on the timing light around the #1 spark plug wire, close to the spark plug and away from the other spark plug wires to avoid interference. Observe the arrow on the clip pointing to the spark plug (if there is such an arrow).

    Power to the strobe light is provided through the red clip. Attach it to a convenient power source. We use the terminal on the right side of the coil (the one with the wires to the automatic choke, backup lights and idle solenoid -- terminal #15). Alternately (and perhaps more conveniently), you can use the positive terminal on the alternator.

    Warning! If you do attach your timing light to the automatic choke connection, be VERY CAREFUL that the black wire from the ignition switch (terminal #15 on the coil) does not accidentally come disconnected from the choke connection and drop to touch the alternator body when the ignition is on. If this happens, you will get a shower of sparks, and worse -- you will burn out your ignition switch!

    Attach the black clip to ground (the bolt on the fuel pump and the rear carburettor nut are convenient places, but make sure the wire doesn't become tangled with the fan belt!).

    Note: It's a good idea to secure the timing light up and away from the fan belt after hooking it up and while starting the bus, to keep the wires from getting tangled up in the fan belt. Tucking it in front of (front is front, remember) the stock air cleaner, or anywhere else in the engine compartment where it is up and away from the fan belt, is a good idea.

    Attach the dwell-tachometer in accordance with the idle procedure above.

    Start the engine. Adjust the idle to 900 rpm using the procedure above.

    Turn off the engine and loosen the distributor clamp bolt (10mm) enough so the distributor requires a strong twist to be moved but will stay where it is moved to.

    Distributor Clamp

    Note: You may find that the nut on the forward end of the clamp bolt turns when you try to loosen or tighten the clamp bolt. It is difficult to get a wrench on this 10mm nut; we finally kept it from turning by wedging a small flat-blade screwdriver against it.


    Stow the timing light, and then restart the bus. Point the timing light at the split in the crankcase and pull the trigger on the timing light. When the trigger on the strobe light is pulled, with the engine running, the strobe produces a very bright light which flashes every time the #1 spark plug fires. This bright light is used to observe the relationship between the timing mark on the crankshaft pulley and the split in the crankcase.

    With the engine idling at 900 rpm, adjust the preliminary timing to the 7.5o BTDC mark by turning the distributor one way or the other.

    Note: Turning the distributor clockwise retards the spark; turning it counter clockwise advances the spark.

    Pull the throttle lever down to increase the engine rpm while you hold the strobe light on the crack in the crankcase, and watch the marks on the crankshaft pulley in the strobe light. The TDC mark and idle marks should appear to move to the left (advance) as the rpm's increase to about 3500 rpm, and the maximum advance timing mark should come into view.

    Turn the distributor one way or the other to set the maximum advance (at about 3500 rpm) to the 30o BTDC mark you made earlier.

    Note: Stated another way -- with the engine running at a high rate of speed (about 3500 rpm), turn the distributor one way or the other to set the spark advance such that the 30o BTDC mark appears in the strobe light at the split in the crankcase.

    Return the engine speed to normal idle.

    Shut off the engine, and while holding the distributor in the correct position, tighten the 10mm distributor clamp bolt. (See the note above regarding the nut on the forward end of the clamp bolt.) Restart the engine and recheck the maximum advance timing.

    Allow the engine to idle and, with all of the vacuum hoses still disconnected and plugged, reset the idle speed to spec (850-900 rpm) per the idle procedure above.

    Check the idle timing and make a mark on the crankcase that that point. In the future you can set the idle timing at this point (vacuum hose removed from the SVDA distributor and plugged).

    Reattach the vacuum hose on the SVDA distributor, and, if applicable, to the vacuum port on the intake manifold.

    Setting the Dual-Vacuum Distributor with a Strobe

    Note: These distributors are timed with both vacuum hoses ATTACHED. If you're not sure which hose goes where, see our article on Dual Vacuum Hoses.

    Make sure that the appropriate timing mark (see above) is clearly visible on the crankshaft pulley (i.e., marked with white paint).

    Attach the inductive pick-up clip on the timing light around the #1 spark plug wire, close to the spark plug and away from the other spark plug wires to avoid interference. Observe the arrow on the clip pointing to the spark plug (if there is such an arrow).

    Power to the strobe light is provided through the red clip. Attach it to the terminal on the right side of the coil (the one with the wires to the automatic choke and idle solenoid -- terminal #15).

    Note: If your bus is equipped with a Capacitive Discharge Ignition system, power to the coil is provided indirectly through the CDI unit. In this case, just attach the red clip on the strobe light to any convenient 12-volt power source. We use the wire to the automatic choke (though some timing lights, when connected in this manner, will prevent the engine from starting -- for a reason we have yet to determine).


    Warning! If you do attach your timing light to the automatic choke connection, be VERY CAREFUL that the wire(s) from the ignition switch do not accidentally become disconnected from the choke connection and drop to touch the alternator body. If this happens, you will get a shower of sparks, and worse -- you will burn out your ignition switch!
    Attach the black clip to ground (the bolt on the fuel pump and the rear carburettor nut are a convenient places, but make sure the wire doesn't become tangled with the fan belt!).

    Attach the dwell-tachometer in accordance with the idle procedure above.

    Start the engine and allow it to idle at about 900 rpm (if the idle speed is other than this, adjust the idle in accordance with the idle adjustment procedure above).

    Point the timing light at the split in the crankcase and pull the trigger on the timing light. When the trigger on the strobe light is pulled, with the engine running, the strobe produces a very bright light which flashes every time the #1 sparkplug fires. This bright light is used to observe the relationship between the timing mark on the crankshaft pulley and the split in the crankcase.

    Note: When timing the double-vacuum advance distributor (two vacuum hoses), the throttle valve in the carburettor must close adequately for accurate timing adjustment. To check, disconnect the vacuum retard hose (attached to the front of the vacuum chamber and rear of the carburettor) with the engine idling. The timing mark should move 15-18mm to the left. If not, the carburettor needs to be adjusted.

    Turn off the engine and loosen the distributor clamp bolt (10mm) enough so the distributor requires a strong twist to be moved but will stay where it is moved to.

    Note: You may find that the nut on the forward end of the clamp bolt turns when you try to loosen or tighten the clamp bolt. It is difficult to get a wrench on this 10mm nut; we finally kept it from turning by wedging a small flat-blade screwdriver against it.

    Restart the bus and aim the timing light at the crankcase pulley at the point where it passes the split in the crankcase. Move the distributor one way or the other until the proper timing mark on the pulley (as seen in the strobe light) lines up with the crack in the crankcase.

    Note: The correct timing setting for the dual-vacuum distributor is 5o After Top Dead Centre (ATDC). This means that as you view the 5o mark at the crankcase split (with the strobe), the TDC mark on the pulley will be about 7.6mm to the RIGHT of the crankcase split.


    Shut off the engine, and while holding the distributor in the correct position, tighten the distributor clamp bolt. (See the note above regarding the nut on the forward end of the clamp bolt.) Restart the engine and recheck the maximum advance timing.

    Note: When you change the timing, the idle speed will also change. The reverse is also true. You will probably have to go back and forth between the idle speed and the timing several times before you get the timing set exactly right at the correct idle speed. It's a bit tedious, but well worth getting it right.
     
  2. Thanks for this how to post, very easy to follow;

    Could any one tell me if this is the same if you have electronic ignition with a 009 distributor.

    I have electronic ignition, followed the post word for word. When it goes back to idle speed from max advance the TDC and 7.5 marking are about 1 cm to left of crack in crank case.

    It runs and pulls well with no dead spots so presuming it is alright, just wondering what the experts can advise.

    Thanks
     
  3. For Type 4 users note that this is from 'Rob and Dave's Aircooled Volkswagen Pages' and is for the Type 1 or 'upright' engine and is not the same procedure for Type 4.

    http://www.tunacan.net/t4/index.shtml and other sites are good resources for Type 4 info.
    :)
     

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