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MG MGA - Dizzy drive gear
|Hey all, can thew dizzy drive gear engage 2 ways, 180 degrees apart? It sure looks that way. Thanks, Tom|
|Tom. Yes it can. In fact, it can be engaged in even more than two ways--one position for each tooth on the gear. That is why you have to put it in so that it points to the two O'clock position with the larger section of the offset uppermost.|
|The drive unit will rotate counter clockwise as it engages its drive gear on the cam shaft. If memory serves, I believe that it starts out with the slot horizontal (larger section of the offset uppermost) and #1 cylinder on TDC on compression. Fully engaged the slot should be on the 2 o'clock/ 8 o'clock axis(and the rotor pointing at #1 cylinder). Check out Barney Gaylord's site for complete directions. Based on personal experience, if you are off a tooth, the distributor body will have to be rotated significantly to achieve correct ignition timing which will be readily apparant to you. Good luck.|
|Careful not to drop the drive into the sump as I have done on my spare engine (must get it out sometime). At least it's not rusting where it is.|
Barney explains all: http://www.mgaguru.com/mgtech/ignition/ig103.htm
|The reason for the "standard" 2 o'clock position is so that the low tension terminal and the high tension leads present themselves for easy connection. It also ensures that the cap retaining clips have room to move. When I bought my car, the dizzy drive had been badly set, so that one of the cap retaining clips was prevented from disengaging properly by the starter body and I had the devil's own job to get the cap off.|
This thread was discussed on 15/10/2012
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