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MG MGA - Help using dwell meter

I'm pursuing a long-overdue tuneup on my 58 and have run into a problem. How do I use the dwell meter? The MGA Tech Session book says that after disconnecting the coil and pulling the plugs, I connect the positive side of the dwell meter to the "distributor side terminal". Is that the nut on the outside edge of the distributor with the two wires that go to the points? Can I connect it to the post on the points? And the negative goes to a ground. What constitutes a decent ground? A bolt on the engine block? Something attached to the frame? I'm getting no reading. It's a used dwell meter with unknown history. Maybe it's not functioning properly? Any simple way to check it? Thanks for any advice you have.

Jim
J Plegue

The dwell meter is not necessary if you set the ponts at the proper opening. However, to answer your question, it depends on the grounding scheme of your car. The proper connection is to the low voltage coil terminal that goes to the distributor. NOT the high voltage wire. This can be done at the coil or at the distributor if you have one with an exposed external connection.

If you have an original POS grounded car, the red meter wire (+) goes to any good ground on the engine or chassis. Head stud, generator bracket or any piece solidly connected. There is little current drawn so it will either work or it will not work. There will be no issue with a reading being accurate. The Black meter wire (-) goes to the low voltage coil terminal marntioned earlier.

If you have a NEG ground car, reverse the colors of the meter leads.

This can be done with the distributor in place and completely enclosed (cap and rotor in situ) to verify the dwell. No internal connections are required. You will, of course have to remove the cap and rotor if your are going to adjust the dwell. In the MG, it is a matter of set- check -reset - recheck - reset - recheck. You get the point (pardon the pun). Setting Dwell instead of point opening distance was a great for GM cars of old when the adjustment was made from outside the distributor with an allen wrench. Not so easily done with the MG setup. It is alos good when the point set is not new and there is metal transfer fron one contact to the other. This made it difficult to use feeler gauges.

With a new set of points or an older set freshly filed flat, the distance method does a pretty good job for a daily driver.

By the way most older analog dwell meters are for 6 and 8 cylinder cars. Use the 8 cyl scale and remember to multiply the 8 cyl angle by 2 to get the 4 cyl reading.

Chuck



Chuck
Chuck Schaefer

Thanks, Chuck. I had the wires crossed. Seems to work fine now. Got the points and timing set and it seems to run fine. Thanks again.
J Plegue

I have a dwell meter but I can't remember the last time I used it. As Chuck mentioned, it was an easy way to set the points on an old Chevy where you could adjust the points with an allen wrench while it was running.

The only good use for the dwell meter is to have a repeatable setting of the points so you may never have to reset the timing. Otherwise the amount of dwell is of very little significance. Set the points gap with your thumbnail, then set the timing. With any amount of dwell from about 15 degrees to 75 degrees it will run okay (as long as the points actually open and close and you get the timing right). You can use the thumb wheel on the original Lucas distributor to make small final adjustment to the timing.

Barney Gaylord

This thread was discussed between 12/05/2007 and 13/05/2007

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