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TR6 TR-6 red distributor rotors

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J

JC1

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Like I'm sure many of you, I ran out and purchased several
"red" distributor rotors when they first became available.
Hearing horror stories of "cars off road" due to low resistance/shorting out of the black distributor rotors that have been in use for decades.

At this point I'm skeptical regarding whether the change over was really a solution to a non-existent problem, or are there actual problems with the black rotors?

I'm eliminating from the discussion obviously defective rotors, as evidenced by a crack that should be detected by casual inspection. I would appreciate your comments and perspective.

Thanks.
 
It's not so much the color of the rotors. IIRC, it's more a factor of a number of recent Lucas-branded (and perhaps others) that were riveted together, said rivet sometimes resulting in the failure. (Someone please correct me if I'm wrong here!)
 
I have also heard about the rivet issue (although I also have some very old rotors with a rivet and they seemed to work fine).

But I think there is another factor at work here as well. Many people have installed various kinds of ignition system upgrade (eg Lucas Sports coil, Pertronix ignition module, etc) followed by either deliberately increasing spark plug gap, or running the same set of plugs longer (so the gap erodes larger). This allows the voltage to go higher (before the spark happens) than was possible using the original coil & points setup; and the higher voltage puts more strain on the wires and rotor.

I have seen a new "black" rotor that was ruined within just a hundred miles of operation, which I believe was due to a Lucas Sports coil combined with a bad plug boot. The rotor looked mechanically perfect, even when I knew it had to be bad. Later examination under a magnifying lens showed a tiny patch of plastic inside the cavity that was less shiny than the rest, which I believe to be the only indication of a carbon track through the center of the rotor, which would shunt the spark voltage to ground (through the distributor shaft).

At any rate, the engine would not even try to run with that rotor installed, but fired right up and ran at least the next 800 miles once we installed a replacement rotor (and removed the bad plug boot).

Maybe (hopefully) the red plastic is a better dielectric and hence better able to withstand increased spark voltage than the plastic used in the black replacement rotors.

BTW, I believe the original rotors were made with Bakelite, which is a very good dielectric. But Bakelite is basically illegal to make now (it releases a toxic chemical), as well as expensive, so I'm certain that the black replacements are made from something else; which apparently is not as good a high voltage dielectric.
 
My TR6 crank was damaged by detonation caused by the junk black riveted rotor. The loose rivet allowed the brass conductor to index out and chopped the distributor cap contacts. The resulting metal to metal contact made a halo of conductive dust inside the cap and consequently the timing was affected. Unfortunately, I was cruising 75 on the Interstate and wearing ear plugs so a change in engine note was not noticed. The increased temperature and drop in oil pressure were finally noticed but the damage was done. No more ear plugs or riveted rotors for me!
 
Randall is right about the originals, which were fine and then the lack of bakelite used today, which surprises me, as the Chinese really could care less about enviro issues to the workers. So I guess that we can just chalk up the bad ones to terrible quality control. In any event, they were junk and left many an owner stranded.
 
High voltage does funny things to the rotor for sure, but a high voltage coil will melt the plastic that runs on the cam. The surprise was how long it took, about 10 seconds. I didn't notice the big high performance American coil until the second time I set the points.


Wayne
 
I have learned with my TR6 that when addressing the ignition system it is important to replace one item at a time and to make sure that the engine runs before moving to the next item. Last year when doing a tune up on my stock '74 with points and no sport coil I found that my brand new rotor from one of the big three was bad right from the box. After replacing the rotor the engine would not run. Put the old one back in and it fired right up. I tried another new rotor and that one was fine. I found that the offending rotor had a crack under the rivet so that the spark went directly to ground. Don't throw out any of your old parts until you are certain that the replacements are functioning as they should.
 
RomanH said:
Don't throw out any of your old parts until you are certain that the replacements are functioning as they should.
Click to expand...
Even then they are worth hanging onto as "known good" spares, IMO. Bad things sometimes do happen while out on the road; and that's not a good time to discover that your new part is bad as well. Instead, carry some "known good" parts for roadside service and then install new when you get home.
 
TR3driver said:
...[C]arry some "known good" parts for roadside service and then install new when you get home.
Click to expand...
Amen to that! I've done more than one <span style="font-style: italic">rescue</span> with rotors that were pushing 50+ years old but still giving excellent service. I learned years ago never to throw something like that away!
 
When I travel. I got no room for spare parts

AWellStockedBoot-1.jpg
 
Bakelite is made from phenol and formaldehyde and is considered the first successful plastic. Its still in use, but mostly in China and India.
 
Don, you do have your priorities in order. A spacer saver spare will give you even more room in the well and it can hold a 10 pack with ice if you line it in plastic.
 
I had a black rotor fail on my 74 TR6. It had more than a few thousand miles on it, with the stock coil and points ignition system. The previous week I had returned from a quick trip from Texas to Pennsylvania and it was running fine. Running an evening errand, I stopped at a red light and ended up being towed home. The part looked perfectly normal. I had to swap it back and forth numerous times before I could believe all I had was a bad rotor. A few weeks after replacing it (with another black one), it failed again. This time I had a spare spark plug on a wire and could test it quickly.

I have a red one in there now, and it's been fine for a few years. I have at least one known good spare rotor in the trunk, and always carry a plug on a wire.

I think heat effects them eventually, and there was a batch of rotors that failed early.
 
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