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How To Use A Timing Light


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#1 Purple Tom

Purple Tom

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Posted 17 March 2008 - 07:50 PM

This isn't written by me, its written by one of the forums technical experts - dklawson. A link to the original thread can be found here

This FAQ relates to any Mini with normal distributor ignition (excluding SPi's), but please note it does NOT contain any specific settings for the timing on any particular Mini.

I've been waiting for your post since you bought the gun.

Let's start with the obvious and basics. There should be a red lead. Connect that to a source of +12V (perhaps the solenoid). The second lead will be the black one and it goes to a good, bare earthing point, preferably on the block or head. The inductive clamp lead goes around the spark plug wire for cylinder #1. Look carefully at the clamp. There MAY be an arrow on it. The arrow should point towards the spark plug.

Start learning to use your gun WITHOUT the advance knob. Turn the knob until the its pointer lines up with its zero mark (turn the advance function OFF). Start the car's engine, point the gun at the timing marks (presumably on the front of your engine) and squeeze the gun's trigger. The strobe should fire each time #1 spark plug fires. This will appear to freeze the relationship of the pulley to the pointer. Read what's going on with the timing marks.

If it's necessary (or you want) to adjust/change your ignition timing, stop the engine and loosen the bolt(s) securing your distributor to the block. JUST BARELY LOOSEN, you don't want the distributor to move at this point. Restart the engine and set the idle speed where your specs say it should be (disconnect and plug the vacuum advance line also). Point the timing light at the pulley and read the relationship of the pointer and the mark on the pulley. Determine if you need to advance or retard the timing. While still firing the timing light, use your other hand to gently twist the dizzy and you'll observe the timing mark on the pulley moves relative to the pointer. Stop when the marks are where you want them then tighten the distributor clamp again.

That's the basics. Now let's move on to using the advance knob. Let's say you have a spec that says your distributor should be giving you an increase of 20 degrees of timing at 3000 RPM. Start the engine and read where the idle advance is using the light as set above. Write it down. Now add the 20 degrees to the idle timing you observed (say you measured 8 BTDC at idle and you add 20 to that for a total of 28 degrees). Turn the advance knob to 28 and point it at the crank pulley. The mark will be NOWHERE close. Now bring the RPM up either using the throttle or the idle screws. When you hit 3000 RPM the mark on the pulley and the zero mark on the pointer should be close to alignment if the advance is working properly. Remember... I made up these numbers. Look up what's right for your engine.

Now let's talk about timing your car to it's maximum advance. Most cars can stand about 32-35 degrees of TOTAL ignition advance. To set this on your engine, disconnect and plug the vacuum advance as mentioned above. Set the gun's advance dial to 32 degrees. With the dizzy clamp loosened, bring the engine RPM up to 4000 RPM using the idle screws. Fire the timing light at the crank pulley and note where the marks are. Turn the dizzy until the zero mark on the pulley lines up with the zero pointer mark, then tighten the dizzy down. Reduce the idle speed to "normal" and use the gun to see where your idle advance is after setting it at 4000 RPM. Write it down. Reconnect the vacuum advance and take the car on a test drive. During the drive put the car under heavy load. Try accelerating uphill in a gear that's higher than called for (a hill that's best taken in 3rd, put the car in 4th and floor the accelerator). If you hear pinging, pull over and use the timing light (at idle will be fine) to retard the timing 2 degrees. Repeat the load testing... retarding the timing in 2 degree steps until you no longer hear pinging. At that point, measure and record your advance at idle.

You have now used your advance timing light to set the maximum ignition advance your engine can handle for its mechanical condition and accounting for the fuel that you buy.

Note that in all the cases where you're using the advance knob... you're using the scale on the advance knob to measure the degrees of advance. You're lining up the zero timing marks on the engine and measuring the degrees of advance based on the knob position on the gun instead.




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