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MG MGA - DM2 distributor service

I'm cleaning up my DM2 40510 distributor before installing in my rebuilt engine. It worked when it was removed, many years ago however. I have a few questions - 1. The workshop manual states "The base plate components are assembled with a special lubricant..." Does this apply to the DM2 distributor, or the earlier one used? What lubricant, and where would it go? 2. Should the centrifugal timing control be lubed with engine oil or just a light weight oil? 3. I'm replacing the vacuum control unit, how should the adjusting nut be set on the new vacuum control? 4. The cloth insulation is frayed on the small conductor attached to the upper base plate, and connected by a terminal to the lower base plate under the screw head attaching the lower base plate to the distributor body. I think this is a ground lead, should I replace it?

Thanks for any comments!

George G.

1. I use a smear of grease between the 2 plates. It's worth giving the plate a good clean. The post that holds the 2 bits together can wear a fair bit and is worth inspecting. If there is a lot of wear on one side you can sometimes persuade the post to rotate 180 degrees with careful use of needle nose pliers, which may improve things. The base plates can be bought new if needed.

2. Again I just use a lick of grease on the weights.

3. I set the adjuster in the mid position, this gives you the most useful range for adjustment.

4. These wires need to be flexible to allow for plate rotation. The insulation is cloth and is often crappy but this doesn't really matter as they are just an earth. Replacing this can be tricky; best left alone unless it is actually broken.

If you remove the roll pin from the drive dog you will be able to remove the distributor shaft from the body and check, clean and relube the bush. I tend to pop the shaft in my lathe and give it a gentle linish with fine grade wet and dry. If there is a lot of wear in the bush it is worth getting the bush replaced; wear here will significantly affect accuracy of timing.

Final trick you can do is check the total mechanical advance. there will be a number stamped on the cam which gives the distributor's mech advance in degrees. Double this for advance at the crank. If you put the dizzy into a vice you can measure the actual advance with a protractor to ensure it is actually what it says it should be. You don't need to worry about slack in the rotor button as this doesn't affect advance, just your measurement.

A Bowie

George - You might want to send your distributor to Jeff at and have him do a complete overhaul of your distributor - well worth the price. Cheers - Dave
DW DuBois

+1 on what Dave says. Jeff does fantastic work. It will come back looking like new and most likely working better than new,much like Dave's work done to my fuel pump :)
gary starr

Send your distributor to Jeff! Ive had three distributors overhauled by him and its definitely worth it. Its much easier to tune your car when you know the springs on the advance are in good shape.
If you just rebuilt your the ancillaries everything must be working correctly to get good performance from a rebuilt engine.

Just my 2cents!

George, use any kind of lube you think it appropriate, there is no special grease for those parts. As your distributor was known to be working fine before, and I ASSUME it was not stored in the cat's outdoor sandbox, or at the bottom of the salt water fish tank, it should be good after that brief time. If you find after the new engine is running that you need a rebuild on the distributor you can do it yourself or send it off. Why does these sites sound so much like phony questions for replies to allow for advertisements for various services and products?
Sam Coleman

This thread was discussed between 15/08/2016 and 31/08/2016

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