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MG MGA - How Do You Wear Your Dizzy

I am taking advantage of the rainy holiday weekend here in the UK to catch up with a few MGA jobs, number one of which is to install my reconditioned original distributor that has been on the shelf for 9 years. This will replace a modern replica that did not have the knurled vacuum advance adjuster.

I used to have the replica dizzy fitted with the vacuum unit pointing about horizontally to the rear. I offered up the original unit likewise and noted that the adjustment unit was very close to fouling my high positioned starter.

The alternative was to rotate it clockwise 90 degrees so that the vacuum unit was close to the vertical. This seems to give good access to the adjuster.

The one diagram I have seen in the workshop manual shows the vacuum unit towards the vertical. Is this the correct position?

Steve
Steve Gyles

Steve:

By changing the position of the distributor drive gear with respect to the respective cam gear you can orient the unit any way you see fit. The end of the engine side of the drive is threaded 5/16" NFT and a 3" or 4 " long hex head bolt can be used to extract it.

Steve
Steve Brandt

Steve G. When the timing marks are aligned, on the compression stroke of number one engine, were is the rotor terminal pointing? It should be pointing to about the "2 O'clock" position.

If it is, no problems with the distributor drive alignment in the engine. Minor problem with how the distributor was oriented when it was last installed. Quite possible to install the distributor in the "correct" position with the vacuum advance can's nose pointing upwards. Also possible to install the dizzy at the 90 degree out, the 180 degree out and the 270 degree out position, all with the distributor drive oriented correctly.

Look to where the rotor is pointing and, if it is at the correct position, simply rotate your dizzy until the vacuum can is pointing upwards, then time the engine.

Les
Les Bengtson

Les and Steve

I don't have any problems timing the distributor or altering the drive shaft etc. I was just wondering if there was a correct (I hate to use the word Concours) orientation for the distributor.

Steve
Steve Gyles

Just to say all fitted (vacuum pointing vertical) and running well with pertronix electronic ignition.

Steve
Steve Gyles

Steve:
If I remember correctly, the manual says the number 1 firing position should be about 2 o'clock.
I think there's a slight advantage to moving that one drive tooth anti-clockwise so that the vacuum pipe doesn't foul the dip stick.
Fraser
Fraser Cooper

Steve. The factory position was with the nipple on the vacuum advance can pointing upwards (generally speaking--most point upwards and to one side). This makes sense from a production standard as it allows a shorter vacuum hose to be run.

Les
Les Bengtson

This thread was discussed between 25/08/2006 and 27/08/2006

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