I measured 33.7mm this morning in a very quick check before work but will measure it properly tonight. Ian reminded me we've fitted bigger valves and I had opened up and equalised the chambers ages ago but this is the first time I have had the engine together enough to actually try the valves on the cam. It seems to be hitting in one place only as far as I can tell but I will mark it up tonight to make sure. Shouldn't be hard to fix I think. With the head just sitting loose it only lifts up a fraction so the contact seems slight.
Simon
Simon