Can someone give me a step by step guide on how to set rocker arm to valve stem clearance in an a15.
The gregory's books I have aren't very clear (not to me anyway) I've done it twice and still theres a tick in the top end.

Dunno a step by step procedure however i do know its 14 thou clearance once the rocker is fully disengaged 9when the piston of that cylinder is at top dead centre.

Take the car for a drive. Get it fully warmed up, so don't just go once around the block.

Pull the rocker cover & the plugs. Turn the engine by hand untill the No. 4 cylinder exhaust valve is just closing, & at the same time, the inlet is just opening. This is described as having the rocker arms 'on the rock' as both are moving during the valve overlap period.

Adjust No 1 cylinder. You will find that No,1 & 4 are linked, as well as No.2 & 3.
Turn the crankshaft over half a turm. You will find that No. 2 cylinder is 'on the rock', so adjust No.3.
Another half turn will put No. 1 cylinder on the rock, so adjust No.4.
Finally another half turn puts No. 3 cylinder 'on the rock'. so adjust No.2

This method guarantees that the lifters for the cylinder that you are adjusting are on the base circle of the cam, which is where you need them to be.
Removing the plugs just makes it easier to turn the engine over.

if you have a rocker arm that is badly worn (a divet where the valve stem contacts the rocker arm) you will not get a true adjustment and maybe cause of noise. you should remove the rocker arm asmembly and replace or reface the rocker arms if needed

Additionally, one key to getting rid of the tap tap tap, is to make sure the gap is correct. The feeler gauge should go in with some drag. It shouldn't feel 'easy' as you pull it out, it should have some drag. But it shouldn't be so tight that you can barely get it in. For the tapping, better to be a bit tight than a bit loose. The spec is 0.35 mm (0.014 inch).

sry double post

Wouldn't be better to have it a bit loose than a bit tight. If its slightly too loose you get noise which is still better than a bit tight which will rapidly kill the valves.

If you can get the feeler gauge between the valve and the rocker, it's not too tight. If it's loose, the tapping sound you hear will eventually wear out the rocker surface area, and the tap will become permanent requiring replacment of parts.

But yes if you get it way too tight you can end up burning a valve. So use a feeler gauge to avoid the problem.

thanks guys Hopefully third time lucky.

Also even though I take the spark plugs out, the engine is still really hard to turn over, I have to get a socket over the bolt in the pulley to turn it over, is this normal?

Take it out of gear ... with the plugs out, it should turn easily by turning the fan. If the fan belt slips that indicates the belt is loose or bad.