I think I misread what was happening. It felt to me as though the rocker arm was slightly sprung so as to tilt it off the pushrod and onto the valve stem. This was because I could easily, with very little finger pressure, push it down onto the pushrod. But I checked more closely, and the rocker arm is actually touching the pushrod, which moves with the rocker arm when I press on it. I think this means the tappet is very soft at the top, and I'm just seeing that internal spring pressure.
Anyway, I had another go at setting the pre-load, idled it fast and filled the radiator and the rest of the cooling system. The fan now comes on when it's hot. I think there's still air in the heater though since it blows cold, but that'll sort itself out on the road I think. By the time I'd finished this the tappets were a lot quieter - still not quite there I think, but I'll take it for a longer drive, then let it cool down and have another go at setting the pre-load.
I took it for a 10 mile drive, and it's driving very nicely. The exhaust sounds different at idle - very slightly deeper I think - but on the road it's the same as it ever was. Pulls smoothly, but I haven't laboured it yet as it should probably be babied a bit for a while.
I haven't yet fitted the oil cooler (didn't want to push my luck), and the oil is getting up to just over 100 degrees when everything is hot. I think it could go higher on a hot day with hard driving. What's normal - do I need to stop everything and fit the oil cooler pronto?
Oil pressure seems ok. I've gone a for 20W50 mineral oil (
Original Heritage from Classic Oils, for it's high ZDDP content (1300ppm), which is good for flat tappets apparently. At 100 degrees I'm getting 2 - 2.5 bar while pootling along at 40mph in top (don't have a tacho, so will have to work out what rpm that was). At the just over 100 degrees and idling at around 1000rpm on my drive I was getting just over 1 bar. So what should I expect at different temperatures/rpms?
Parked it on my drive and checked underneath for leaks - not a single leak of anything, anywhere. You think *you're* surprised. I count 24 hose clips in the engine bay alone, plus various pipe gaskets, o-rings, sensors etc. Must try not to be too smug - pride before a fall etc.....