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Can't seem to find a replacement distr. cap like the one on my TR4

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dixonh2 Avatar
dixonh2 Silver Member dixon harris
wellington, FL, USA   USA
1951 MG TD "N/a"
I intend to replace all ignition parts on my TR4 engine. Obviously I am nonmechanical.

The photos show my distr, cap.It loads the coil wire and sparkplug wires from the side. But it has a U shaped cut-out on the side to accommodate a wire that I cannot identify.

Any idea where I can find a replacement cap like this?

What is the function of that wire connection that the U shaped aperture accommodates?

Thanks from Clueless



Dixon H Harris
Wellington Florida

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dixonh2 Avatar
dixonh2 Silver Member dixon harris
wellington, FL, USA   USA
1951 MG TD "N/a"
Rut; That was it
Thanks

Still have no clue what that 6th wire connects to. Leads to my dash. Will have to trace it.



Dixon H Harris
Wellington Florida

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
It should lead to the ignition coil (which in turn has a wire to the ignition switch on the dash).

Briefly, the ignition points inside the distributor control the low tension (12v) current through the ignition coil primary winding. When they are closed, current flows and builds up a magnetic field in the magnetic core inside the coil housing. At the appropriate moment, the points open, interrupting the primary current through the coil. That causes the magnetic field to collapse very quickly, which causes a high voltage in the secondary winding. This goes out the tower on top and into the center of the distributor cap, where it is directed by the rotor to the spark plug for the correct cylinder. There, it jumps the gap at the end of the spark plug, creating a spark, which in turn ignites the fuel/air mixture.

A very clever system, especially considering it was invented around 1900. Used almost exclusively for over 100 years (tho of course the points were quickly replaced by transistors once solid state electronics became reliable and cheap). Distributors are long gone, of course, but chances are that your modern car still uses the same inductive method of generating spark voltage. (Generally, most modern cars have an coil for each cylinder or each pair of cylinders, so the distributor is no longer needed.)



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

Vila Avatar
Vila Robert Beers
Mechanicsburg, PA, USA   USA
1933 Chevrolet Master "The 33"
1962 Triumph TR4 "The TR4"
1964 Vespa VNB 125 "The Old Vespa"
1984 BMW 633CSi "The 633"    & more
Yes, that smaller wire with the red insulated connector should go directly to the Coil.

You should be able to get that style distributor Cap at, BP Northwest, Moss Motors, The Roadster Factory, Little British Car Company, and others.



Vila

Visit my personal website at: www.jakegingervila.wixsite.com/bobs-vintage-cars-

dixonh2 Avatar
dixonh2 Silver Member dixon harris
wellington, FL, USA   USA
1951 MG TD "N/a"
Randall I appreciate your extensive comments. Very instructive and useful.

Yes, that wire I asked about does lead from the distr. to one side of the coil.

Sent to MossM for the appropriate distr,cap.

Sent also for a rotor. Hope it's the correct one.

Now,Randall, what parts do I send for to properly rebuild the distributor which has a lot of miles on it. Got a MossM number for me?

I have NGK plugs already Moss Number 117-261. Are these okay?

Thanks very much.



Dixon H Harris
Wellington Florida

dixonh2 Avatar
dixonh2 Silver Member dixon harris
wellington, FL, USA   USA
1951 MG TD "N/a"
Robert.

What a great website, beautiful

DIxon

wellington, fl



Dixon H Harris
Wellington Florida

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Doing the distributor is probably not a DIY job. Takes special tools, etc. Unfortunately, I can't think of the man's name offhand, but I'm sure someone else does.

I've no idea what Moss 117-261 is, so I'm no help there. But NGK makes good plugs, and I'm sure Moss wouldn't sell something too badly unsuitable. Plus you've already got them, so give them a try. Run them awhile, then inspect the tips. In general, the problems revealed will indicate something else wrong (poor mixture, burning oil, etc), but sometimes going one range hotter or colder on the plugs can help compensate.

Or, if they fail early or you're not happy with them, you can try Champion L87YC (which is what I'm using these days after too many failures with the Bosch Platinum plugs). They are usually readily available at local auto parts stores; or I think I bought my last batch from RockAuto https://www.rockauto.com/en/catalog/triumph,1963,tr4,2.1l+l4,1491602,ignition,spark+plug,7212



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

tr4head Avatar
tr4head Rob B
Atlanta, GA, USA   USA
First, congrats on getting the best TR out there! That is a standard design with screw in wires. Yours is ok aftermarket type, the OEM will be Lucas and say so on the top of cap. Either is fine, are easily available thru Moss Motors, Roadster factory and others. I have and use both. The lead out of the top in the "u shape" area is the HT (high tension) lead that goes to your distributor terminal.

Geo Hahn Avatar
Mt Lemmon, AZ, USA   USA
I have always had good luck with NOS (or nearly new) caps from eBay sellers. Brass instead of aluminum, possibly better made, scarcely more than the Intermotor replacement and anyway i like the look.



Copper core wires (my opinion) are a better choice with these caps as you are relying on the contact made by that piercing screw.

Edited for clarity



Edited 1 time(s). Last edit at 2019-01-18 12:43 PM by Geo Hahn.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
It's been a few years back, but ISTR the last one I got from TRF had the Lucas logo and brass terminals.

In reply to # 1590116 by Geo Hahn Soild core wires (my opinion) are a better choice with these caps as you are relying on the contact made by that piercing screw.

I definitely agree, assuming that by "solid core" you mean stranded copper. The carbon in "carbon core" wires tends to burn out around those piercing screws where you can't see it.



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

Savannah dog Gold Member Julian Carter
Lincolnton, GA, USA   USA
Don't forget to get Red rotor. Several members have had trouble using the Black rotor.

Never mind, wrong car, Was thinking of my 48' TC



Edited 1 time(s). Last edit at 2019-01-18 10:01 AM by Savannah dog.

sdebaker Silver Member Paul Rollins
Vancouver, WA, USA   USA
In reply to # 1589973 by dixonh2 I intend to replace all ignition parts on my TR4 engine. Obviously I am nonmechanical.

The photos show my distr, cap.It loads the coil wire and sparkplug wires from the side. But it has a U shaped cut-out on the side to accommodate a wire that I cannot identify.

Any idea where I can find a replacement cap like this?

What is the function of that wire connection that the U shaped aperture accommodates?

Thanks from Clueless
This probably sounds too thrifty, but I hate to throw away something that is still quite usable.

If a distributor cap is still physically sound, no short tracks, and the interior contacts are only lightly burned, I service it and reuse it. My process is simple. Using a Dremel (R) type tool with a small, wire wheel, I clean the burned deposit off the contacts. At the least, I may replace the cap on the engine and keep the refreshed one in the car as a spare.

Similarly, I will dress used points that are not too far gone and keep them in the car for roadside replacement of a failed set.

Condensers I usually don't change. Older ones are generally better than current (pardon the pun) ones. Some new ones are junk right out of the box, or become junk too soon after replacement. Always keep a proven spare in the car.

I also re-use rotors, by dressing the tips and cleaning the center-contact point with steel wool. Same story as condensers -- old ones are typically better. New, black ones with a rivet are very unreliable. I have had a few short, on one trip it was two of them. I've learned that lesson. Always keep spares of these. Red seem to be better, but I have seen quality differences among these, too..

tirnipgreen Avatar
tirnipgreen Silver Member Ryals Cheek
Ellijay, GA, USA   USA
1965 Triumph TR4 "YANG"
Get one from Advanced Distributors....in Minnesota (?)

Sienna 73 Mike Sullivan
Whitmore lake, MI, USA   USA
You can get a Beck Arnley cap on Amazon. Beck Arnley sources the closest thing to an oem part and markets the part under their name. I purchased the cap on my tr6 and a friend purchased one for his tr4.(made in England) We are happy with our purchase and best of all, the price is right. You can got to the Beck Arnley web site, input your car and see all parts available. I also picked up a spare slave for my clutch for a very reasonable price.

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