Blowing Distributor Rotors

[Scotty]

Are there special distributor rotors that I should be using if I have 'electronic points' in my Lucas Distributor?

I ask this because I have now blown a handful of rotors in a short period of time and it's a downright Scooby Doo mystery. I'm not seeing any difference in voltage anywhere along the line.

My Distributor is eating SS rotors like candy and some NOS German distributor rotors are fairing a little better but are also going that way. I tried some from Amazon and my distributor just laughs at them.

Any idea what is wrong or what I can try? My kit didn't come with a special rotor and I'm leaning on picking one up of some kind to try and see if it works. Ideas?

 

[sunalp]

What type of "electronic points" are you using? I've had mixed results with Pertronix as of late. The magnet ring wouldn't push down
on the distributor shaft and actually put too much pressure on the distributor cap. It was strange as the cap would actually move
as the rotor turned. Never experienced that before. I took the cap off and the brush was completely worn and the rotor was
also. Converted the dizzy back to points, no issues.

Having said that, there have been a bunch of rotors that have been defective. There are many posts about that.

 

[DanR]

Tim R had a video that showed an issue with the rotors.... seems most are coming out of China

 

[Jay Laifman]

I can't imagine how a Pertronix would damage a rotor. What do you mean by "blown"?

On another car, I have Pertronix, and one rotor on the market has too long of a base. So you have to file off some of the bottom.

But also be sure the magnetic ring is fully pushed down. It is a precise fit, and if not done exactly right, it will ride high.

 

[Scotty]

I can't imagine how a Pertronix would damage a rotor. What do you mean by "blown"?

On another car, I have Pertronix, and one rotor on the market has too long of a base. So you have to file off some of the bottom.

But also be sure the magnetic ring is fully pushed down. It is a precise fit, and if not done exactly right, it will ride high.

I will check the ring. That’s a good one.

When I say blown, I’ve had the rotor crack, melted the plastic around the metal arrow point, actually take the coating off of one of the metal points and a few other things. When it goes, the car wont fire up, when I swap it, it fires right up. The cap and wires are new and the coil is proven reliable to this point.

I will definitely check the magnetic ring and make sure it’s actually all the way down. It looked that way but just to make sure.

 

[Jay Laifman]

Measure how high the rotor sits with the ring on and with it off. That might help detect an issue there.

I'd also add that I am a fan of Pertronix. I don't happen to have it on my Alpine merely because I used Lumination on it decades ago and it's still working just fine. I have Pertronix though on other cars. Personally, I found that the quality of points and condensers out there now has suffered so much, that I like the consistency of Pertronix.

 

[absunbeam]

A victim of Lucas boxed rotor from China. Always carry a tow rope JIC for your disabled Harrington and an extra rotor.

 

[Tim R]

It sounds like you are suffering from pattern rotor arms. I now only use distributor caps and rotor arms from The Distributor Doctor in the UK. I use these with electronic ignition but they can be used with standard points. They are very high quality and are much better than anything originally made. The tolerances are correct and it makes a massive difference to the car.


Tim R

 

[greenbeam]

This is happening all over the old car world. It is caused by junk replacement parts from China.

It is recommended to use only rotor and cap from a reputable ignition shop, replace both rotor and cap at the same time. The same hassles are happening with condensors - blowing after a couple of months.

Distributor Doctor in the UK seems to be the go-to place there, Performance Ignition Services in AUS, not sure about the US.

I've had a Pertronix and a 'Flame Thrower' coil on the car for about 20 years now, and it has had no effect on the rotor. I've changed the rotor and cap twice in that time, once when I fitted the Pertronix module, and once recently.
Cheers,
Paul.

 

[Alpine Addict]

I have had two fail in quick succession. The first did not get me off my driveway and the 2nd only just got me around the corner.

 

[Jay Laifman]

It sort of begs the question, when to replace a rotor and how to restore one. I've always been quick to replace them when I do a full tune up. But I remember early on, I would lightly sand the rotor with a crocus cloth and all seemed fine. If not for these physical collapses, when should we even bother? And is a light burnishing a better thing to do?

I can tell you, that stash of used rotors I have (at least I hope I still have them) have now become more valuable to me.

 

[Tim R]

Jay,

Both the electrode in the distributor cap and the tip of the rotor arm erode as they work. That is why they are a service part. You can clean them up if they get tarnished but you actually erode a bit more when you do that. The tolerance between the two tips is important. The pattern parts are shoddily made and have a huge gap, which makes the cars harder to start and can lead to the spark finding different routes.
Your old ones are worth keeping as spares but it is always worth fitting a high quality, correctly dimensioned cap and rotor when you service the car. This is why we use Distributor Doctor. His parts are 100% correct, you will have someone similar in the U.S. I am sure.

Tim R