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MG MGA - Distr. Rotor Question

I'm putting my new distributor and setting static timing. Does the rotor postion have to be in a certain quadrant of it's rotation?

The reason I is if position the slot with rotor at 1:00 then distributor doesnt seat all the way, maybe 1mm from flush. If I spin it 180 degrees to 7:00 in the slot, she slips right in.

Can I use it in this position and just rearrange the plug wires?

Am working on it away from home at the moment so a quick reply is appreciated...
Judd Irland

It must be in the way that lets the distributor go fully home - the slot is offset so it will only go in correctly. The rotor pointing to 7 o'clock means that you are timing it on #4 instead of #1. If you haven't had the drive gear out of the block or already changed wire positions, then the wires will be in the correct positions, leave them.

FR Millmore

Remove valve cover and look at the rocker arms. Rotate crankshaft until the rear two rocker arms are rocking, one going up whole the other is going down. Turn to position where both arms are the same height. This will be Top Dead Center with #4 on exhaust and #1 on compression.

Then remove distributor cap and look at the rotor. If the distributor drive gear is installed in correct orientation, the rotor will be pointing in the direction of #1 spark plug. The drive gear has 9 teeth, so each tooth error would dislocate the rotor by 40 degrees. To properly index the drive gear see here:

When this is correct, position the dizzy body so the vacuum unit will point straight up. Rotate crankshaft to set timing mark at desired static timing (suggest 12 degrees BTDC). Turn dizzy body anti-clockwise until points are closed, then turn dizzy body slowly clockwise until points just start to open (point of spark), and clamp it down.

Look at the distributor cap, and find the HT terminal that will be closest to #1 spark plug when installed. The wire in this HT socket will go to #1 spark plug. Rotor turns anti-clockwise when running, and firing order is 1-3-4-2. So starting with the #1 HT terminal and progressing anti-clockwise around the dizzy cap, install plug wires for #1, #3, #4, and #2 spark plugs in that order.

If the dizzy drive gear is installed wrong, and the rotor points another direction, you can still make it run without fixing the drive gear. Same instructions apply, except the #1 HT terminal will be the one closest to where the rotor happens to be pointing. While you can make it run this way, it is advisable to correct the configuration so it will not fool the next mechanic (who might be you).
Barney Gaylord

Thanks for your help guys. I had watched the valves to find TDC originally. I assumed I was not familiar enough with all this, so I just trusted that the PO had it right before as it was supposedly running when they parked it in 1983. Voila!!! Success!

With your help, I saved a life today, thanks FRM and Barney
Judd Irland

This thread was discussed on 19/12/2010

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