Head Gasket ??

The info that I have says torque to 12-15 foot pounds in an 'X' pattern. And I would buy a gasket for it rather than make one because the ones for heads are partially metal rather than all asbestos. I don't claim to be an expert so before you do anything see what everyone else has to say

You need a torque wrench.
Should anyway.
You could make one out of copper plate.
Prolly should change the base gasket.
My 1 motor acts the same way when the base gasket is gone.

Your the torque wrench! all the bolts are 10mm so never use anything bigger than a 1/4 ratchet or a 10mm spanner and dont jump on em

If the gasket looks OK just heat it up with a blowtorch and let it air cool, then reassemble it, if the gasket is not cracked then its not the problem. A little leakage out of the head is almost normal with these things.

If you really want to get rid of the leakage you should sand the mating surfaces smooth on a piece of glass covered in sandpaper.

BTW i wouldn't advise buying a new base gasket, just make one out of a roll of gasket paper. The whole roll will cost you about the same as one gasket will, and you can use it for all your gasket needs.