ferguson t20 valve timing

i wonder if anyone can help me,how can i check valve timing on the 85mm standard petrol engine,i think the crankshaft and camshaft sprockets have been changed sometime as there are no marks on them,i have changed the chain.thanks

I found this in the archives. I hope this may help you. Please read it well to make sure this is what you need.
valve timing

To check the valve timing, first you need to find
the TDC (top dead center) position for the #1 and
4 cylinder (they run together, so for now work
with the #1 cylinder).

If you can't find a mark on the flywheel or front
pulley, remove the #1 spark plug, reach in the
plug hole with a thin screw driver or piece of
wire, hand turn the engine until the piston comes
to the top. Carefully monitor the position of the
piston as you very slowly rock the crank back and
forth until you find TDC as best you can. Put an
obvious mark on the pulley or flywheel where you
can find TDC again. This won't be an exact TDC,
but close enough for checking the valve timing.

Now, with the valve cover off, look at the
position of the #1 rockers and the #4 rockers. If
timed properly the rockers on #1 OR #4 will be in
"overlap" position. Again rock the crank back and
forth, watch the rockers on #1 and #4. One set
will teeter back and forth as you rock the crank
forward and backward.

Find the place, when turning the crank clockwise
that the exhaust just closes, and the intake just
begins to open. Recheck the TDC mark. If it is
aligned, or within 3 to 4 degrees, the valve
timing is correct.

If the engine is not fully assembled, you can do the same thing by watching the position of the lifters. Hold them against the cam and feel when the exhaust just runs off the lobe and the intake just begins to rise.