Practically Classics Forum

After 20/30 mins running our Vauxhall PA engine begins to faulter, eventually stall & finally becomes impossible to restart until cooled down, although engine temp is normal. We've been told the problem is the contact breaker plastic heel melts, & softens thus closing the points gap because the dizzy is low down & to the rear of the engine bay away from cooling airflow. Have you ever heard of such a problem?

Yes, but only in cases where the foam pad that carries the oil for the cam has been left out during fitting, or where the heel was made from modern, synthetic plastics rather than Urea or similar resins. Is this a Delco Distributor? If so, there's a guy on the Saab Club board who rebuilds nothing else and he's very good at it, even making his own resins. Can't bring the name to mind just now but I'll have a look over the weekend if it'll help.

All that said; what makes the plastic heel reform when the engine has cooled down? Original resin wouldn't melt in the first place and modern plastic can melt but couldn't reform itself under the pressure of the spring.
So is there any chance this could be fuel vapourisation and that your mechanic is wrong?

Or possibly the coil failing when it is hot. I have had that before, eventually failing to work at all.

could you fit an electronic ignition?

Agree with John's post above - get a decent quality set of points (and condensor and rotor arm while you're at it) and make sure the cam is lubricated and it'll be fine.

As above, and if there is an interference suppressor on the coil, try disconnecting that.

Thank you, people, its good to have your support. I've already fitted a new coil and on stationary running alone it seems it may have helped, though still concerned about taking the car far. Have bought a set of genuine new old stock points for the Delco dizzy. The heel seems a kind of composite material, brown & appears a little more robust than the newer plastic/nylon ones. Does this sound like "fibre" to anyone?

By the way JPB, I think you're correct - I can't believe even a slightly melted heel would reform itself under pressure. Could the heel I've described be the resins you mention?

I too have wondered about fuel vaporisation - thanks for that. Meanwhile, I would be grateful to be able to contact this Saab Club guy. Many thanks for that also.

Hope I can let you all know soon about the results of all this.

Yes, your description of the heel and the fact that the contact set is a proper, old stock one would suggest to me that it's some sort of resin such as Bakelite, or as you suggest; perhaps a fibrous material like Presspahn or Paxolin, in any case not the sort of plastic that would suffer as a result of the temperature inside the distributor being - possibly - slightly higher than the temperature inside a distributor located further from a source of heat.

I shall now go off and try to find the Saab bloke. I should be able to find some old email from him as we have communicated within the past few years, so my first job is to open Thunderbird Mail and click on "Import all", then see what happens.

TerryG wrote:Or possibly the coil failing when it is hot. I have had that before, eventually failing to work at all.

Totally agree, had this issue on my old Scimitar SE6a

I had very similar problems on my singer a few weeks back.
Starting fine. Ok until hot when it would start to splutter and stop, restarting after a few mins.
Had to be a fuel issue?
Changed the coil as it was an old one anyways. The car was already running a period lucas electronic ignition system.

Whilst running checks on the car (in my cosy garage) the ignition failed completely.
As a stop gap, I bought a brand new Accuspark distributor. It took about 10 mins to fit and adjust. It has made a huge difference to the car overall and whilst I have since bought a NOS lucas distribuor, I am torn whether to fit it or not!.
I wold definitely be looking at the ignition side of things.

Kev