does anyone know how muc you can skim an early x flow head (chambered) head, in order to rais compression, ie can it go down to being flat, i know it might be easier to get a newer head but this one is nicely ported and has an unleaded conversion, thanks in advance,johnq

No, that's absolutely the wrong way to go about it! - either sell that head somewhere like Turbosport and use the (probably decent amount of) money you'll get to buy a good version of the much more common flat head OR keep it and get some flat top lotus twin cam pistons. Skimming it to the extent you're talking about will probably render it worthless

Advice over.......as it happens I have some twin cam pistons I'm never going to use which I'm willing to sell on BUT you will need almost certainly need a rebore to fit them - u2u me if you're interested

He's right you know. To get the info you need check out Wallage and Grommit sorry Peter and John Wallage Rebuilding and tuning X-flows and Pintos. It is however common consensus that the chambered head's aren't much use for tuning. Also you don't know how much if at all your head has already been skimmed so you'd have to do some pretty accurate measurements of squish clearances. I thought about offering to swap ur head for my GT flat head cos I'd rather have lead-free head than the performance initially but I don't think this would do either of us any favours. D. Beddows alternative is an interesting one well worth looking into cos you can keep ur lead free head which isn't cheap. Though we all know the cheapest way for power is just to go Zetec there's just something about crossflows.