Distributor caps?

[Dorian]

My Mk 2 PI developed a bit of a misfire over the course of a couple of weeks, and after pulling plug leads off to pick which cylinder I decided it was number 4. I checked the plug and it was clean, and gapped right but I changed it anyway. Then the fault went to cylinder 1! After some faffing (I had a GT6 before and that ate rotor arms, so I thought it was that) I looked in the dizzy cap and found that 4 of the "contacts" inside had been arcing through the bakelite.
       The cap looks fairly new(I haven't had the car long) but it doesn't have any makers marks on it--Are there any known problems with pattern caps like the rotor arm issue?
       I've sent off for a new one so hopefully the car will be a runner again soon.

[Nick Jones]

There are lots of very rubbish rotor arms and caps for the Triumph 6 around - this includes the ones packaged as Lucas.  Back when I still had a distributor I had loads of problems and eventually reclaimed a tatty old cap and rotor arm from a scrappy which worked far better than any of the new ones.

However, recently decent rotor arms at least (not sure about caps) have come to the market and are being sold by Rarebits for Classics and probably others too.  Well worth seeking these out as the others are hopeless, especially when used with electronic ignition.

Nick

[Lord Sorbington]

My dizzy cap was in a Lucas box, bought from Fitchetts a year ago, has been fine, minimal wear after 3000 miles.  Kept the old one as a just in case....  Running on points, not electrickery :)

[heraldcoupe]

I hear about poor caps, but I've not experienced any failures myself.
There have been several failure modes with the older rotor arms, one of which is tracking through the plastic. Carbon is used as a filler in the plastic, so it's little surprise that the insulation can break down! The same is likely to be true of distributor caps, the plastic compound in some types is very similar to that used on cheap rotor arms. The new rotor arms have a nylon body, there is no carbon filler.
Buying Lucas is no guarantee of quality, all of the old-fashioned stuff is bought in and re-branded. If you can find old stock Lucas in the Red packets then that's likely to be of genuine Lucas manufacture - it will generally have the company name moulded in the plastic (not printed) if it's genuine.
I have seen some distributor caps where the contacts are poorly machined, with evidence of swarf. I have never been supplied with any like this, but I inspect incoming stock for this kind of problem. It's a different issue I know, but I see it as an indicator of quality control with the manufacturer,
Cheers,
Bill.

[Dorian]

    Yes, I've had the rotor arm tracking problem before on my GT6, which is why I thought it was that. I ordered a new dizzy cap but I got an email today saying I'm on back order as they're out of stock. So I've ordered another from somewhere else and the delivery drivers can race!