Pirie593, Just a foot note if you use a good quality gasket cement on all surfaces (both sides gasket + barrel + head) you will have no problems with it leaking.
Also tension head down as well to recomended torque will help.
20 foot pounds is the setting on a 480.
I do this on my 250 Red devils, 480 and CR 500 and have no problem with leaking.
I also just read in the wanted section that a bloke has recomended a (I will stand corrected) silcon type bonder, from my experience these do not work as good as the (brand name) Aviation form-a-gasket which does not set hard and can be used time and time again. Any good automotive store will have it.
Shane