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MG MGA - Timing light connections

Getting ready to time the engine.
Bought one of those advance type timing lights.
The directions indicate connecting the red alligator clip to the positive post on the battery and the black clip to an engine ground for a car with negative ground.
BUT, as you know, our cars came with a positive ground, and for those, the directions say to connect the black clip to the negative battery post and the red clip to engine ground.
Simple enough, but, with the batteries located where they are, the timing light cables don't reach without cutting the cables and extending them.
I've been told somewhere back when, that, rather than doing that, I can connect a timing light clip to the starter switch under the hood and the other clip to ground instead.

If this is true, my question is, remembering the timing light's directions for positive ground cars, which clip (red or black) do I clip to which part of the starter switch; the connection that goes to the starter or the connection that goes to the battery?
L.R. deOlazarra

For a positive ground car:

Black to the powered terminal on the start switch or a live terminal on the fuse block
Red to the mounting bolt for the heater air control

This keeps all the cables nice and out of the way, but may not work if the cables are too short to see the timing marks under the car.

If you use the starter switch, the terminal going to the starter is only live when the knob is pulled, so you need to go to the other one that also has the brown cable attached for the live feed to the regulator.
dominic clancy

With my light, I found that even after connecting the clip intended for the battery to an alternative feed in the bonnet as Dominic explains, there was still not sufficient cable length to comfortably reach round and under the front of the car to use the timing light, so I extended the cables to make life easier. You may also find you will need to carefully feed the cable from the spark lead along a shorter route, straight down so that it reaches underneath (watch out you dont get it fouled by fan).
More sensible people have turned the engine so the timing marks are lined up, and then painted additional marks at the top. Would recommend that, even though I haven't got around to it myself, so that you can see what is happening as you make small adjustments to the dissy
Graham M V

It never fails to amaze me; sitting in my garage near San Francisco needing a solution to a problem and, within the hour, what I need is provided by a couple helpful souls in Switzerland and the U.K. Just amazing...
Thanks for clearing it up, Dominic.
Graham; yes, the paint marks on the top... With it at TDC, I put them on the part of the timing chain cover that I could see from the top, along with the corresponding pulley mark, the day before yesterday. Try as I could, I couldn't do it properly without removing the generator and upper radiator hose so I could get decent access, but now that it's all together, I'm glad it's done.
Again, thanks...
L.R. deOlazarra

This thread was discussed on 09/09/2010

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