Hello T J ,
Y Blockhead was right on the money. I had the same issue with the zenith leaking nanno amounts past the float valve. The firewall valve on my 31 roadster leaked enough to pressure it through the float valve. Put in a new one with the new viton seat and it still leaked. Finally I installed a positive in line shutoff and my issue was over. Been four years now and no issues at all and yes it will leak as you say when you face it uphill and park it. Just remember to shut the in line off and you're all set. Think my in line came from Brattons for about 50.00 Good luck Dutie
