75 petcock leak

[Dom]

I'm trying to solve a leak on my left hand petcock, it coming from the oval o ring I believe. I have cleaned up the mating faces and replaced the o ring with a new one, from what i can see the o ring itself which I think is from Yambits is too small in profile so isn't compressing enough before the petcock body comes into contact with the tank. Does anyone have any suggestions?

 

[Jan_P]

I have never replaced that oval O -ring . but every winter remove the petcock on my 1980.
I keep the O -ring and smear some liquid gasket on it
The one I have had good results with is plastic padding liquid gasket.
Perhaps not available in UK but that seems to be god.
I had a friend with leaking Cadillac radiator hoses. On the verge to a breakdown
I saved him to.
Other brands might be a replacement but I have that.

 

[Dom]

I'll try that or at least something similar if I can find one that isn't destroyed by petrol or ethanol, its fine with 1/2 a tank of fuel but as soon as I brim it the pressure becomes to much for it.