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MG TD TF 1500 - Distributer Cam

Am about to purchase electronic points for my TD. I have two distributers I can use. One out of my blown engine and one out of the new engine. Engines are only about 3000 apart. Distributer for old engine (4144) is DKY4A 40046D DA34 --->9 48. New distributer(eng. 7205) is DKY4A 40162A DA37 ---> 11 50.

There is a difference in the cams of the two. First problem is trying to figure out exactly what cam I have in each. It appears the 40046D has a High Lift and the 4016A has an Asymmetric but it is very difficult to tell.


Is there a way of telling which cam by measuring with a micrometer?

Is one better than the other as far as performance?

Does the distributer cam have to be matched to the type of camshaft (19 thousanth vs 12 thousanth)?
Bruce Cunha

The high lift cam is alomost square with slightly rounded corners. The other two look almost alike. The cam shape varies the rate of points opening/closing, and the duration that they are closed or open (the dwell angle). This alters the time the field builds up in the coil, and when the points open it collapses and causes the spark. The electronic ignitions don't care what cam you have, either they cover it up and use a rotating magnet (Hall effect), or and LED with a "chopper" disk (the old Pirhana/Crane). The electronics take care of the duration issues rather than the dwell angle. Someone please correct me if I'm off somewhere in this- it has been a while since points! George
George Butz

Thanks George

So, the reason you need to give the type of cam is so they send you a magnet that will fit over the specific cam. That would make sense.

I found pictures of the three different cams on Skip Kelsey's web page, but even with those, it is difficult to tell which one is which.

Can anyone tell me about the 40048D Distributor? According to Moss they have kits for the TC that go for the 40162A Distributor, and they have another kit for the TD/TF with a distributor number of 40367D
Bruce Cunha

Took some pictures of the distributors.
Bruce Cunha

Bruce - If you have the shop manual, they have a picture of all three cams in it. At first glance, it looks like there is no way to tell the difference between the two of them, but if you look at the picture, it shows the slot in the top for the rotor arm locating key to fit in and it is at a different location on the two look alike cams. From there is is easy to identify your cam. Cheers - Dave
David DuBois

A telephone call to Moss { technical I think} will provide you with the dimensions of the three. Decifering between an Asymetrical and Symetrical is not easy by eye ball alone.
Terry O'Brien

Bruce, you'll get a lot better technical advice and save yourself a bunch of bucks if you use Skip Kelsey as your source for the pertronix. Usual disclaimers, just a very satisfied customer.
Bud Krueger


In the East, I've dealt with Joe Curto for my Pertronics and found his advice and support excellent.


Gord Clark
Rockburn, Qué.
Gordon A. Clark

Got to agree with Bud & Gord...either Skip or Joe will also know to ask if your "poss or neg" ground first! The $5 or $10 more you would save from some discount place will go up in smoke in a hurry if that's not right!
Once you let the "smoke" out of a Pertronix they are not much good for anything. (new "smoke" is co$tly!)
David 55 TF1500 #7427
David Sheward

Why the sudden interest in cigar lighters???
John James

I have one in the pannel I mounted under my dash...(GPS/Cell phone)....the one on ebay has a really nice MG logo on it...but the price is pretty high!
David Sheward

Hi All

Thanks for the great advise as usual.

I called Skip (old TD friend from way back). he is currently not able to take calls or fill orders. Verna, his wife said he had some back surgery recently.

I sent him an e-mail telling him once he is up and around to get back to me. As he also has the 8mm x 1.0 Helicoil. Figured I will get the two items together from him.

Bruce Cunha

Check with NAPA. I purchased some from them about a year ago. It was not in stock but they located them for me.
Sandy sanders
Hudson Florida
conrad sanders

The 40048 (not 40046) distributor was fitted to the TC and TB, and was superseded by the 40162 distributor, which was also fitted to the YT and the TD (and Mark II) up to engine 20941. The advance curves of both distributors are the same and all such cars used the MG862/171 camshaft, although any camshaft will, in fact, fit.
Regarding the points cam, both the early symmetric cam (square with round corners) and the later high lift cam (convex faces) were used in both distributors. However, the suffix A, B or C after the number indicate that a symmetric cam was originally fitted, and the suffix D and onwards indicate that a high lift cam was originally fitted. The cams are interchangeable, so later owners may have swapped cams. As other people have indicated, with electronic ignition, the type of cam does not matter, although there should be no excess bearing movement at the points cam, or along the main distributor shaft. For normal ignition, I prefer the high lift cam.
Both the above distributors were designed to be used in the early oval water hole blocks, as the later round water hole blocks had distributors with shorter stems; thus the 40048/40162 distributors will fit the later blocks, but a spacer will be needed along the shaft.
Roger Wilson

This thread was discussed between 07/01/2005 and 14/01/2005

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