Noa has a Yamar engine which is serviced different, but we had a Volvo TMD22 on our previous boat. The camshaft cover on the TMD serves as the upper part of the camshaft bearing. When you disassemble it to check the valve clearence, you will either need a special tool (three camshaft moutings which hold down the camshaft) made by Volvo or you find a machine shop/build them by yourself.
In case the clearance is outside the tolerance 0,2-0,4 inlet or 0,3-0,5 outlet, you need to readjust to 0,25-0,35 inlet and 0,35-0,45 outlet. If the clearence is inbetween the first tolerance, you don´t need to readjust.
Walter (Noa, SM2K #436)