OK I've made a start. I decided to replace all the exhaust valves which makes life a little easier but the seats are pitted enough that there's no way I could get them done by hand this side of Christmas. Even using a drill I'm having to reach a compromise and leave a degree of pitting. The aim is to get a few more miles out of this engine before fitting another which I'm currently rebuilding. It was unfortunate when it decided to burn two valves at just the wrong time. My P4 is a 1958 90 which should have a 2.6 litre straight size, inlet over exhaust engine. However someone in the past had fitted a 1954 75 engine of 2103cc which is now rather tired - hence the current work. I bought a 1961 100 2.6 engine plus overdrive gearbox to replace it and bring the car back closer to original spec but with a small but significant improvement. The 100 engine has a 7 bearing crank and roller tappets but without the higher compression of the 110 or 3 litre engines. In my view this makes it the best version for everyday use. Mine is fairly unworn needing just a hone of the bores and new rings, shells, etc. Unfortunately, parts are seriously expensive with specialists asking £260 for a set of std (and therefore rare) main bearing shells, for example! On the positive side, the 2103 engine is now pretty rare so I should be able to recoup some costs when I make the swap.