Engine and clutch (stock)/Dynamic ignition timing

From Motorious

Overview

Stroboscopic timing light being used to check timing.

NOTE! If you are setting up a new installation or some other instance where the original timing cannot be checked, it is recommended to first set the static timing with the engine off and then use the stroboscopic timing light to check the timing dynamically (i.e. while running).

There are two basic methods of checking and adjusting ignition timing. Static timing is described in Static ignition timing. It is done with the engine off. The engine is rotated by hand with a wrench on the pulley and the opening of the points is indicated by a test light. Dynamic timing is described in the article below. It is measured using a stroboscopic timing light with the engine running (and warm). The timing light senses the electricity in the plug wire as the spark plug fires and flashes a built-in strobe light at the same moment to highlight the position of the crankshaft pulley. The flash against the pulley markings identifies the position of the crankshaft and pistons.

Ignition timing can be defined as the degree of crankshaft rotation at which the spark is "triggered". This is accomplished by having an adjustable rotating trigger (in the case of the Air Cooled VW, a set of breaker points) and a four lobed distributor cam which opens and closes those points. The instant that the points "open" or "break contact" is the instant that the spark from the coil is "triggered" and sent to the spark plug.

The adjustment of this timing is accomplished by rotating the distributor body and thus the ignition breaker points around the distributor cam which is in constant and fixed mesh with the crankshaft. This makes the points open earlier or later relative to the position of the engine as it rotates.

Measuring the exact moment of ignition is accomplished by various means, each of which determines the position at which the ignition breaker points open or break contact.

Preparation

• Mark the crankshaft pulley as described in crankshaft pulley marking.
• Determine the correct timing setting for your engine.
• If you have a 6-volt car and your timing light requires 12 volts, you can power the light from a separate 12-volt battery.

Step 1: Connect the timing light.

Inductive pickup connection for the timing light (cylinder #1). Power for the timing light can be taken from the alternator's positive terminal, but this is not possible for generators (use coil terminal 15 (+) instead). Connect the timing light according to the manufacturer's instructions, with engine off for safety. Inductive pickup goes on the spark plug wire for cylinder #1 as close to the spark plug as possible. TIP! Convenient ground connections in the engine compartment include the nuts/bolts which hold the fuel pump and carburetor in place; the bumper; the bolts which hold the ignition coil to the fan shroud. Select a location which allows you to keep the wires away from the engine's moving parts (i.e. belts and pulleys). Paint is generally an insulator, so seek bare metal for your connections. Convenient 12V connections in the engine compartment include connection #15 on the coil (with the wires running to the carburetor...usually the right side) and possibly the alternator. WARNING: Damage may result! Make sure that all of the wires are arranged so as not to get caught in the moving pulleys and belt nor get fouled in the carburetor cable and linkage.

Step 2 (optional): Connect the tachometer.

A combination dwell/RPM/voltage meter connected with green lead on coil Terminal #1 and black lead on ground (bolt securing coil strap to fan housing). NOTE! The Tachometer is not nessessary for stock timing as idle and full advance at wherever it occurs is all we need to know. With the engine off, connect the tachometer with the green lead on coil terminal #1 (usually on the left side) and black lead on any convenient ground. Again, take care to ensure no wires will get caught in any moving engine parts.

Step 3: Loosen the distributor clamp to free the distributor to rotate in the case.

Loosening the distributor clamp. Use the socket wrench to loosen the bolt on the distributor clamp. The clamp should only be slightly loosened (i.e. nothing removed) to allow the distributor to be rotated by hand. NOTE! Keep the distributor in the same position (i.e. don't rotate it yet) so the engine will still run!

Step 4: Start / warm the engine.

Warm up the engine so that the choke is fully off and the idle is settled down (850-900 RPM). If your engine's idle speed is too high, it will be necessary to adjust the idle speed.

Step 5: Operate timing light according to manufacturer's instructions.

Timing light in use. Aim the timing light beam at the top of the pulley, parallel with crankshaft centerline and in line with the split in the crankcase. The timing light will strobe the timing mark at the moment when the spark is occuring in cylinder #1.

Step 6: Rotate the distributor body to reach the desired timing setting.

Rotating the distributor. The correct timing setting is determined by several factors including the types of distributor and carburetor on your engine. While the engine is running, the RPM, load, and throttle opening will produce various amounts of timing advance. For the stock Air-Cooled VW we are interested only in the advance at idle and the total advance produced in the 3000 RPM area.

Step 7: Tighten the distributor clamp and re-check your work.

Tightening the distributor clamp. CAUTION: Injury may result! Be careful not to contact the rotating belt with your hands or tools.

Cleanup / next steps

Recheck your work.

Related links

• Static ignition timing
• Ignition timing on Wikipedia
• Ignition Coil on Made-in-China.com

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