Timing gauge for easier dwell adjustment and more
Posted: Fri Jun 24, 2016 4:16 pm
I could have sworn that I'd posted this before, but couldn't find it. So I'll put it up again.
If you haven't converted to electronic ignition yet, you've probably spent many worthwhile hours adjusting the points. This involves removing the distributor cap and rotor and checking the points gap. If it's wrong, you loosen the screw, move the non-stationary plate just a wee little bit, and tighten the screw. Then you put everything back together, turn the ignition on, start the engine, and hook up a dwell-tach meter. The adjustment will be wrong. You turn off the engine, go to the back, remove the cap and rotor, and try again, loosening the screw and moving the plate another wee bit. Then you put everything back together again (not forgetting the rotor like you did the last time) and start the engine. When you hook up the dwell-tach again, you will find that you have moved the points not one wee bit, but two wee bits. You turn off the engine....
If you've had this experience, you might want to try another way. Print out this handy gauge on a piece of thick paper or card stock:
Laminate it if you want to.
Now attach it to the crankshaft pulley with a button magnet, as shown here:
Connect your voltmeter or timing light or whatever to the #13 terminal on the coil (where you usually clip your timing light or dwell-tach). Turn on the ignition, put the car in neutral, and rotate the engine to the point where the VOM shows 12 volts or the light goes on. Rotate the gauge so that the zero lines up with the crank-case seam. Rotate the engine clockwise until the light goes off or the voltage reads zero. Read the gauge. That's your dwell.
Now you can adjust the dwell simply by adjusting the points, turning the ignition on, and reading the result. There's no need to re-assemble the distributor or start the engine, although you may want to shut off the ignition or disconnect the wire at terminal 15 on the coil while you're actually adjusting the points, to prevent sparky things from happening. I think you'll find that this procedure will reduce your time spent on the job by quite a bit
Note that you don't have to worry about where top dead center is and all that. All you're measuring is the range of the degrees of rotation when the points are on. But once the dwell is right, you can use the gauge to mark out the various points that you'll need for using your strobe, once you've sussed out where top dead center is on your particular beast. (If you've got a stock pulley and a reference book like the Idiot Book or the Bentley, the notches in the pulley should give you an idea where that is.) I put a drop of white paint at the 32 degree mark BTDC, so I can check how the advance is working with my particular combination of carburetor and distributor.
If you haven't converted to electronic ignition yet, you've probably spent many worthwhile hours adjusting the points. This involves removing the distributor cap and rotor and checking the points gap. If it's wrong, you loosen the screw, move the non-stationary plate just a wee little bit, and tighten the screw. Then you put everything back together, turn the ignition on, start the engine, and hook up a dwell-tach meter. The adjustment will be wrong. You turn off the engine, go to the back, remove the cap and rotor, and try again, loosening the screw and moving the plate another wee bit. Then you put everything back together again (not forgetting the rotor like you did the last time) and start the engine. When you hook up the dwell-tach again, you will find that you have moved the points not one wee bit, but two wee bits. You turn off the engine....
If you've had this experience, you might want to try another way. Print out this handy gauge on a piece of thick paper or card stock:
Laminate it if you want to.
Now attach it to the crankshaft pulley with a button magnet, as shown here:
Connect your voltmeter or timing light or whatever to the #13 terminal on the coil (where you usually clip your timing light or dwell-tach). Turn on the ignition, put the car in neutral, and rotate the engine to the point where the VOM shows 12 volts or the light goes on. Rotate the gauge so that the zero lines up with the crank-case seam. Rotate the engine clockwise until the light goes off or the voltage reads zero. Read the gauge. That's your dwell.
Now you can adjust the dwell simply by adjusting the points, turning the ignition on, and reading the result. There's no need to re-assemble the distributor or start the engine, although you may want to shut off the ignition or disconnect the wire at terminal 15 on the coil while you're actually adjusting the points, to prevent sparky things from happening. I think you'll find that this procedure will reduce your time spent on the job by quite a bit
Note that you don't have to worry about where top dead center is and all that. All you're measuring is the range of the degrees of rotation when the points are on. But once the dwell is right, you can use the gauge to mark out the various points that you'll need for using your strobe, once you've sussed out where top dead center is on your particular beast. (If you've got a stock pulley and a reference book like the Idiot Book or the Bentley, the notches in the pulley should give you an idea where that is.) I put a drop of white paint at the 32 degree mark BTDC, so I can check how the advance is working with my particular combination of carburetor and distributor.