CAMSHAFT CONTRADICTION
Bryan Moore raised a pertinent point in reference to my Triumph 3T rebuild. A while back, he wrote in about the excessive cam wear his 1937 Norton ES2 suffered after having had the cam followers reprofiled. I suggested that the problem could be the kind of paper/ scissors/stone effect you can get from mixing different sorts of hardening.
Ha! Bryan now quietly reminds me of this after I glibly announced recently that I was fitting later stelllite-faced followers to replace worn out case-hardened ones in the 3T engine.
Fair point, Bryan; if I’m honest, that didn’t cross my mind – but in my defence, I think it’s OK. With the Triumph, casehardened followers were used on all models up until 1951, when they were superseded by stellite. There’s no indication that the cams changed at the same time, I think it was just a running change and if you ordered new followers after 1951 they would have been stellite, so they must be compatible with the original cams.
But funnily enough, having just pulled apart my crashed Sunbeam engine, I found a problem of my own. Twenty years ago, I had the cams skimmed and re-hardened (possibly tuftrided) and the followers built up with weld (stellite, I assume) and reshaped. The cams still look great, but one – just one – of the followers has completely worn away. Why? If it’s incompatible with the cam hardening, why not both? Did one follower get too hot during regrinding? I don’t think so, as stellite is very heat resistant. It’s a mystery – the only sure thig is that, after 20 years, it’s too late to go back and complain.
Lucky I had that crash last year or I’d never have discovered that problem!