I replaced the head gasket on the old engine and it is quite easy. Get yourself to Halfords, they have a set of feeler gauges for not too much. Adjustment is simply a case of loosening the lock nut on the tappet (10mm I think) and then turning the threaded tappet to adjust the clearance, then you tighten up the lock nut whilst holding the tappet steady so as not to disturb the settings. It can take several tries to get it right but as there's only 2 it is no biggy. Make a note of which pushrod is inlet and outlet as well. Also if you have a leak on the head gaket check around the cylinder base gasket as well, both of mine had gone together for some reason though it was only a slight weep of oil on the outside and so I changed them both.
I actually still have the old engine handy so I might take that apart and have a little look about before I try it on my current one thanks anyway I think I will do the important gaskets while I'm there it actually looks like the gasket below the head gasket that is leaking. Thanks for all the replys
Little tip when doing the tappets, to avoid the adjustment going out when tightening the lock nut, adjust the tappet tight then back off to the correct setting this takes up any slack in the thread of the adjuster before tightening the lock nut.
