being as you are going to use the valvola,
start with a pipe length of 8 1/4 to 8 3/8 inches measured alng side the motor starting dead even with the glow plug to teh high point of the plug.
head clearance as per the instructions i wrote earlier in this thread.
you will need the 18 degree header from Ian Folkson
www.iansboats.co.uk
start fat on the needle and let the motor slowly break in. put a small wheel collar on the water pipe just above the nipple on the rudder blade. adjust it so that you can just barely blow thru it. the 21's need HEAT to work properly.
if there is anything elsee i can help you with, please feel free to write.
[email protected]
carl