Ignition Timing Lights & Positive Earth

[John and Suzanne Payne]

I have a Series IV Alpine with Pertronix ignition and positive earth.

– Will a regular induction timing light work to set the timing?
– Would it have be attached with negative to earth as is usual or positive lead to earth to match the cars system?
– Would the induction pick-up for the plug lead have to be attached facing a different way to account for the spark running the other way on positive earth?
– Is it possible to damage the timing light if connected incorrectly?
– Any recommendations on a suitable timing light to buy?

[Joe and Kerch McConlogue]

My timing light is nearly as old as my Alpine, but it has two power leads, positive and negative as well as the inductive pickup. With an incandescent lamp it is not sensitive to orientation of the inductive pickup. Modern lights if using LEDs might be direction sensitive, but I’m not familiar with their circuitry. No harm done, if it doesn’t work in one direction, just turn it around. I’m sure those with more info will chime in.

[Sean Johnson]

It doesn’t matter for the induction lead… place the red power lead on ground, black on coil or brown wire terminal on fuse box. Just set the timing on a Big Healey yesterday.. they are all originally Positive ground.

On the pertrox unit… somethings they don’t tell you… you have to use resistor spark plug leads.. Using stranded metal core wires will fry the amplifier unit. you should use their coil and remove the ballast resistor from the circuit. the pertronix coils are internally ballasted. if you use their coil and keep the OE external ballast the voltage signal to the amplifier will be insufficient for proper operation.. been there, done that!

[Bob and Jean Webb]

I have to agree with Joe. As far as using a Pertronix in place of the points on an Alpine I have always used a Lucas coil, ballast resistor and a set of Lucas plug wires from the early 70’s. When it goes to a SUNI I install plug wires that were a set of NOS when I bought them in the early 80’s. I don’t use them other than for being judged.

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[John and Suzanne Payne]

To provide some feedback and ask another couple of questions.

After some research, I finally bought an Innova 3568 Digital Timing Light off Amazon. It’s somewhat high end and has a rev counter built in which is very convenient. Based on the helpful advice above and a good article from Moss Motors that I found – INDUCTION TIMING LIGHTS AND POSITIVE GROUND CARS – https://mossmotoring.com/induction-timing-lights-positive-ground-cars/ – the timing light worked well. As appears to be the case with most of them on the market, the leads were too short to reach the battery, so I used a trickle charger. According to the Moss article the leads provide power to the light so a suitable 12V source is all that is required connected positive to positive and negative to negative. In fact, some people use an old battery. As noted in a response above, it didn’t make any difference which way the induction lead faced.

The timing light revealed that the timing was very advanced and in trying to retard it back to about 10 degrees BTDC which is in the recommended range, there was not enough anticlockwise movement on the distributor before it contacted the engine block. On the former points system the distibutor was angled at about 45 degrees to the engine block with the vacuum advance pointing towards the oil filter. Is there some adjustment on a Pertronix system that compensates for this? Running the car this advanced produced poor performance, misfiring, and backfiring. Also once warm it would not start again.

Ballast Resistor – I don’t believe my car (1964 Series IV from the UK) has one. There is nothing obvious and again using a Moss Motors tip – Ballast Resistor – How to Test – https://www.youtube.com/watch?v=pWxJmbm5V3s – the results indicated the car does not have one (it is a British model not North American). From what I understand the presence/absence of a ballast resistor can be problematic with Pertronix, though I am using a Pertronix coil. I believe the plug leads are OK, being brand new from Sunbeam Specialties, who also suppled the Pertronix equipment.

Some thoughts on the above would be much appreciated.

[Gary and Maureen Corbett]

John – Hi, I’m not familiar with the Petronix system enough to know how to adjust the position of it on the mounting plate inside the distributor. The timing problem seems odd though given how many of these systems have probably been sold to date – are there any similar postings about timing problems on MG or Triumph forums? Do you have another distributor to compare the internals with to see if there is something different with your distributor?

The only other solution I can think of is to drop the oil pan and remove the oil pump to reindex the distributor timing gear to the camshaft.

I would also suggest reposting your Petronix issue on the Forum here as a separate topic under its own title to solicit more specific responses.

Gary

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