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MG MGB Technical - Side-Plug Distributor Cap

The PO put a Beck Arnley distributor cap on the car which has the top mount leads. I'm thinking that a Lucas cap with the side mount leads would make for a cleaner set up. The Lucas side mount type seems to have no way to keep moisture out of the cap. Am I right? Is this a problem with this distributor cap?
Neal Zick

Actually, the wires fit very tight into the cap, so moisture intrusion is not a problem. Go ahead and do it, but you need to buy the wires specifically made for the cap. A carbon-core wire will deteriorate quickly if you can even get a good contact in the first place.
Jeff Schlemmer

What about silicone core leads? Can they be used instead of the copper core leads?
Neal Zick

Silicon is the insulating jacket of the wire and does not convey electricity. Standard "performance" silicon wires are not going to be the solid core type that work best with the side entry cap. Wire sets such as Moss's 171-628 are best for this application.
Jeff Schlemmer

Neal
My experience with the side entry cap when the water control valve started to leak, was that water did enter one plug wire and I developed a misfire and had to replace the valve and the distributor cap. I have had problems using the carbon wires with that cap. However, with a carbon wire from coil to cap and the rest copper wires with 7mm hi quality insulation (and a new heater valve) I've been maintenance free for several thousand miles.

Barry
Barry Parkinson

Water or even condensation does get in, and is responsible for most cap death. Put a gob of silicon grease in the hole, then push the wire in - be sure it's bottomed - and tighten the screw. Pull moderately on the wire to be positive the screw has gone through the side. Wipe off any excess silicon grease, No water can get in now. Even carbon string wires will work, but not a good choice. Neil is correct - there are silicon conductive core wires, better than carbon string. Solid copper or magnetosuppressive wire-wound conductors are best.
FRM
FR Millmore

Magnetosuppressive wire-wound conductors? What are they? What makes them the "best"? Who makes them?
Neal Zick

Bosch make a nice set of "universal" solid core wires. They all have right angle plug leads attached, but no distributor cap ends. Part numbers 09-985 4-cylinder, 09-986 and 09-987 6, and 8, respectively. They are a good value, and product. Peter
Peter Caldwell

They have a tensile core like fiberglass, with a small diameter wire, usually a nickle alloy, wrapped around it from end to end, like a guitar or piano string. The magnetic field generated by any current moving along a conductor generates and radiates Radio Frequency Interference, which screws up communications equipment. The resistance wire - carbon string or silicone - is a cheap way to reduce this. In the magnetosuppressive type, the fields around the wound wire interfere with each other, stopping the RFI, without introducing as much resistance. Since they have actual wire, and are in effect a very long spring, they are more robust than the resistor types. Many high end wire manufacturers make them, usually their "best".
FRM
FR Millmore

Does Lucas make them? If not Lucas, Then who does?
Neal Zick

Neal,
The Lucas "side entry" had an optional "Glove" which fitted over the cap and the five wires (hence the name "Glove" ) to provide an extra measure of water resistance.
The original Mini and many other Lucas equipped cars had them as standard fitting.
Perhaps Moss or Vivky Brit may be able to help?

Sorry but not living in the US I am not able to help much further.

Cheers , Pete.
Peter Thomas

Neal-
For all practical purposes, Lucas does not exist anymore, just a brand; it's been sold off so many times that it is irrelevant, although there is an industrial segment that is still valid. Maybe why so much "Lucas" stuff is now garbage.
Google MSW wires.
The wires were first made by MSW, which means "magneto-suppressive wire"! A number of manufacturers make them, probably under license; the last ones I got came from JC Whitney at about the price of midrange silicone wires. I've seen them in many parts stores under different names. Only trouble is, they tend to be hideous colors.
The protective boot seemed like a good idea, but while it was good for heavy rain on the transverse cars, it tended to get condensation under it in damp weather, leading to tracking and dead caps; it was very difficult to clean and dry off the cap. I took all mine off and had less problems.
FRM
FR Millmore

Neal,

if you ask for clear transparent copper core wires at the BOSCH service, they should be able to order this for you. Straight spark plug sockets of 1 Kohm resistance are also offered in their range.
These combination helps you to see immediately wether there is something wrong with these items.

The old style of distributer cap for the D25 with the little screws to fix the wires, this setup has never given me trouble within decades. The more modern caps with the light alloy points are more prone to contact corrosion due to the mix af materials there.
It is also a good Idea to keep the bonnet open, when the car is parked in the garage.
When you are used to store it this way, you will allways have a look upon your engine before after driving the car and can see mecanical problems as a leeking heater valve or other, more essential falts long before they will bring you into trouble.

Ralph
Ralph

Are the Crane Firewire leads of the Magnetosuppressive type?
Neal Zick

The Crane wires probably are such, and may be the same wire as MSW, or a cheaper version thereof. For more than you ever wanted to know, and a splendid treatise on marketing BS:
http://www.magnecor.com/magnecor1/main.htm
Read all the documents provided in the menu to the left.
Note that EMI is a more general term than RFI (which applies mostly to comm equipment)
Note also that you don't have to worry about EMI other than the RFI part for MGB.
And, remember that for the side entry cap you need 7mm wire, since the bigger and more sophisticated wires won't go in the holes.
FRM
FR Millmore

Magnecor makes the following claim-

"unlike all other performance wires, can safely be installed into the original 7mm size spark plug wire retainers despite the larger 8.5mm (Magnecor KV85) cable size."

Does this mean that they will fit the Lucas side entry distributor cap?
Neal Zick

No, that reference is to the little notched holders the wires go into on many engines, to keep them from flopping about all over the engine.
FRM
FR Millmore

I have the side entry cap on my '64 and found the yellow bumble bee wire to work very well.

The reason -- the wire are held in place by a screw, which makes the newer "high teck" wire prone to faliure at the connections.

Bumble bee wire is readily available.

glg
glg

I have the side-plug cap. I purchased it before MG '96 so I would have the "authentic" cap. I have had a few problems with individual wires, but the cap is still doing well. The wire problems had to do with the wire coming apart where the screw pierces the insulation. The quick fix is to snip off the end of the wire and reconnect.

That said, when I replace the cap, I plan to use the later cap so I can use off-the-shelf wires.

I have not tried the bumble bee wire -- just using whatever Moss sold at the time.
Bill Barge

How big a lead can the later cap take?
Neal Zick

When I purchased the car, it had the later cap. I purchased plug wires at the auto parts store, so whatever you could get there is what I used. That setup worked great. I switched the cap for looks.
Bill Barge

I'm surprised that nobody seems to know the answer, so I am sending this thread back to the top for another try at finding out. How big a diameter spark plug lead can the top mount distributor cap take? 8mm? 8.5mm?



Neal Zick

8mm fits a bit snug in aftermarket 25d top plug caps. I use 7mm suppressor silicone wires. They still will "chirp" alarms on some cars as I drive by (stray RFI), but they keep the motor noise at a resonable level even with my MSD 6A Electronic ign , Accel Super coil and pertronix breakerless set up. The slightest amount of condensation in my cap and she wont start. But a quick spray of WD-40 directly into the cap always fix's it immediatly.
D.A. Abbott

What brand spark plug leads do you use?
Neal Zick

This thread was discussed between 02/09/2006 and 11/09/2006

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