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MG MGA - More Pertronic, Also ignition wires

Thanks to all for your ongoing help!

Dominic and Les's advice on polarity worked perfectly.

Jeff Zorn did know what I should be buying (how's you know Les?)

Here are some follow-ups:

1) The Pertronic kit came with a clear piece of plastic about 1 1/4" long and 3/8" wide with no reference on what its for in the instructions. What's it for?

2) I got an ignition wire kit for this project. Its the one with the long wire that you are supposed to cut up and screw on the plug adaptors. I also want to replace the high tension wire from the distributor to the coil. On the existing wire into the coil body there is a copper cap that has some sharp prongs that go into the wire body, presumably to improve conductivity. I can't find a replacement cap in the kit?????? Did I not order the right part number?
Tysen

Tysen. As I mentioned on the previous thread, while you were posting, Jeff is "a friend of a very valued friend". Plus, he is an MGA owner himself and I have never heard a bad word about him.

As to your follow up questions:

1. I do not know. Call the tech support at Petronix and ask them. I do not remember this piece from the three kits I have helped to install (two I-H Scout IIs and a 75 B). Let us see--i.e. report back to us, on how good their tech support is.

2. I am not sure what you received. For the MGA, with the original coil, there should be a stranded wire from the coil to the distributor cap. On the coil end of wire, you remove about 1/8" of the insultion, poke the wire through the screw in cap, install the special washer, spread the strands of the wire to lie parallel to the surface of the washer and screw the cap piece into the coil. All of the MGAs, and MGBs up until 1967 used this type of coil. The other end of the wire was put into the central terminal of the distributor cap and secured with a set screw which punched through the insulation and made contact with the wires in the core. The spark plug wires were supplied with a cap to fit over the spark plug terminal and the other end to be fitted to the dizzy cap and secured with set screws. If you have a coil with a push in style nose, or a distributor cap for the push in style connectors, the system you have may not be appropriate. Without seeing what you have, it is hard to make such a determination.

Les
Les Bengtson

Here is a link to a photo of what I presently have. You will see the end of the wire that goes into the end of the coil, Next to it you will see the cap I was refering to. Note that one "leg" of the cap has broken off, however you can get a sense of how it would work.

Just for what its worth these are the codes on the coil

C1Z
12 Volt
309
9E
http://i53.photobucket.com/albums/g64/tbm66/IMG_0364.jpg

Tysen

Jeff and his group are indeed a pleasure to work with and I have the benefit of being able to stop by to pick up my parts on the way home from work........
Tysen

Tysen. The wire and connector seem to be the push in style which was used on the later, Lucas 25D4 distributor caps and the later model coils. I do not have an MGA coil immediately to hand, so cannot say for certain. Look at the "nose" of the coil and see if the internal part is treaded. If it is, the coil needs a stranded wire, the special washer and a screw in cap. If, as I suspect, you have a later model coil, the one with the push in connection, you will see no threads and a metal piece to receive the push in style of connection.

The distributor cap for the DM 2 distributor is identical to the later (68 to 74) Lucas 25D4 distributor cap. This has the push in connections whereas the earlier model DM 2 and 25D4 caps had the screw type connections (a set screw that had to be backed out, the wire pushed into the hole in the cap, and the screw tightened until it penetrated the wire through the insulation).

I have used the later style "wires", the ones with the carbon strand cores, in such distributor caps without problem. However, connection to the original style, screw in, coils was a significant problem.

Please be so kind as to post a photo of your coil nose and distributor cap. That would make things easier to diagnose.

Les
Les Bengtson

Les,

Thanks for your patience and help.

Here's a photo of the coil, clearly no threads inside the nose.

http://i53.photobucket.com/albums/g64/tbm66/IMG_0366.jpg

Here is a photo of the distributor cap. Near as I can tell the screws have a sharp point that penetrates the wire.

http://i53.photobucket.com/albums/g64/tbm66/IMG_0368.jpg

Tysen

Tysen. You have a later model coil, prpbably a Lucas, which uses the more modern style of wire connectors i.e. the push in style.

I would replace the distributor cap with the later model (1968-74) and get myself a good quality set of wires to fit it.

I have been using the Robert Bosch wires for a number of years with very good results.

Please keep us informed.

Les
Les Bengtson

I would suggest that you read the instructions again - they are quite good.

The clear piece of plastic is for setting the gap between the sender (which fits over the distributor shaft underneath the rotor arm) and the receiver which fits in place of the contact breaker (aka points).

You set the space between the sender and receiver using the plastic like a feeler gauge. If the gap is bigger that the plastic, the system will not work.

I had to file the hole in the plate to get a big enough range in the adjustment to get the gap small enough.


The coil connection should be a standard push fit HT lead at the coil end. Normally, one cable in the kit will have these both ends for fitting between a coil and a distributor cap (most mfrs used a push fit cap after they gave up on the screw fittings for the cap and coils) You can just go and buy one of these at the local motor store, and then cut down to length for connecting to the distributor cap you have. Take the coil with you and test fit the lead in the end of it. The picture you post shows the fitting has been broken on the wire, I have never seen these fitting available individually, as they need a special tool to crimp them onto the HT lead.
dominic clancy

Thanks for the feed back.

Where would one find the Bosch wires?

Jeff doesn't appear to carry them..

Should they be suppressed or unsuppressed?

Is there a performance difference?

I tend to like the appearance of original unless there is a noticable performance difference.
Tysen

Tysen. I purchase them at my local BAP (British Auto Parts) store. The manager used to be an MGB GT owner and keeps a good stock of MG parts on hand. What he does not keep in stock may be ordered from their warehouse for next day delivery. But, any good quality brand of "1968-1980" wires will work fine with the proper distributor cap.

Les
Les Bengtson

Dominic,

I was worried that was the case. The adaptor plate for the pertronics fits no less than three different posts and screw holes perfectly, however the sending and receiving units aren't even close if that is indeed the distance they are supposed to be apart.
Tysen

Tysen, some of the pertronix kits are adjustable while others are not. The 25D and DM2 distributor kits are non-adjustable, but all the kits come with the plastic "feeler."

Wear to the central pivot of the points plate can cause the gap to increase between your Pertronix trigger wheel and module. If there is significant play it will cause ignition problems.
Jeff
Jeff Schlemmer

Jeff

Although the DM2 version is "non adjustable" I had problems with mine until I "adjusted" he fitting so that the gap between sensor and sender was the same as the thickness of the plastic. After that it worked just fine.
dominic clancy

I spoke to Pertronix tech support. Apparently the system should work fine up to 70 thousandths of an inch! That's like three thicknesses of plastic!

Tysen

70 thou is 1.778mm. The Plastic in my kit measures 1.5mm with a quick wave through the micrometer, and to me the extra .3mm is a rather narrow margin of error. Without modifying the mounting, the gap was more than 4mm in my case, so that's why it wouldn't work until fettled.
dominic clancy

Dominic, thanks for the explanation. I know there are many oportunities for different (and worn) points plates to be installed, so I could see where the gap can become an issue. I've installed dozens of these kits, but haven't come across one that's "out of spec" yet, although I did have one module that had the holes drilled slightly offset. One had to be opened up to slip it onto their adapter plate.

Compared to other brand kits I've installed, Pertronix are by far the most fool proof!
Jeff
Jeff Schlemmer

This thread was discussed between 29/06/2006 and 01/07/2006

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