Regardless of levels of knowledge or experience, we all need a bit of assistance from time to time, and itʼs good to be reminded that there is an army of specialists just waiting to help keep our steeds performing as they should.
Since the trip to Le Mans, the Vegemite Special has suffered from intermittently poor running: pulling like a (small) train one minute, then stuttering with what felt like pinking or a misfire the next. I had replaced various ignition parts, changed the timing and altered the mixture, but all to no avail, and I needed to begin ruling things out, starting with the distributor. Cue Martin Jay, aka the Distributor Doctor.
Martin tested the Lucas 43D extensively, plotting the advance curve and performance in its as-received state. This immediately threw up several rather obvious issues. First, worn bushings meant that it was over-advancing at the upper end, but he also identified that the low-grade condenser was causing a misfire and that the spring on the contact-breaker points was very poorly profiled, occasionally shorting out on the distributor body.
The 43D was dismantled into its basic parts, cleaned, rebushed, adjusted and reassembled – fitted with consumables of known (and excellent) quality – before it returned to this corner of Berkshire with a much better profile now plotted on the graph. I had high hopes that popping the rejuvenated unit back into the Special would instantly have it running better than ever and, for a brief moment, it was… Until the pinking returned and the car struggled to pull under load.
Martinʼs excellent work did at least mean that I could rule out the distributor, but it was then time to look in another direction. When I removed just one valve early in the build, I noticed considerable carbon build-up on the stem, but I was also aware that the plugs were fouling. This was something Iʼd presumed was down to the rich mixture, although closer inspection revealed that the back plug was wet with oil.
My carʼs era of Reliant cylinder head uses ʻumbrellaʼ stem seals – designed to ride up and down the stem – but they also let more oil get past than a fixed design. I wondered if it was coming down the worn guides and into the combustion chamber. A chat with my mate and local engine guru James Goldstraw resulted in the agreement that we would rebuild the head with some new guides, improved stem seals, a valve and seat cut/reface, and a head skim.
