Cylinder Head & Valves
Sooner or later the cylinder head will need attention. It's a good idea to do some inspection work even if all seems well, especially if you do not now the history of the engine. The A10 rocker box looks like one of those everlasting inventions, as long as the oil supply is right. I've change the tappet adjusting bolts & nuts to some very light allen-type from SRM, as the originals square-headed bolts were quite destroyed & difficult to adjust..
Loosen all 4 tappet adjusting bolts, then loosen the rocker box, 5 screws & 4 nuts. Loosen the 9 head bolts in sequence, a little at a time. Decarb the combustion chamber with a rounded knife, the deposits gets quite soft if left to soak for a while in some degreaser or petrol (keep the plugs in). While the combustion chamber is filled up you can check for leaky valves. If the liquid flows out quickly trough one or several valves remedial work is definitely needed.
Regrinding the valves is the first thing to try. Remove the valve with a suitable valve compressor tool (I use an inexpensive slightly modified car valve tool) then grind it for a short period with a fine grinding paste. Any serious pitting will quickly show. If deep pits are apparent it's better to go for new valves than trying to grind the damage away, as too much grinding will recess the valve into the head. In my case I will have to get a set of new valves, new springs & new guides. May just as well go for a total overhaul with lead-free inserts. For the moment I grind them a little and continue driving while I evaluate what to do & when to do it...
Clean the valve stem and valve guide, scraping
away all carbon deposits. Then insert the valve in the guide & check for play. If
excessive (everything over barely noticeable) new guides and\or new valves are needed.
Worn guides will among other things draw oil from the top into the cylinder. Check the
springs' length. Weakened springs will give trouble at higher rpm. Make 100% sure the
valve locking collets are properly in place, you may not want to find out what happens if
a valve falls into the cylinder while you're doing 80 mph. Check the pushrods for