According to Bill Piggotts bible to the original TR2/3 the TR3a was fitted with an AC Delco radiator cap at 4lbs pressure.
I had fitted a new cap when I bought the car as the spring on the original had separated from the cap. It worked, but fell apart when you removed it. But this was one of the cheap Moss radiator caps and had a simple galvanised finish.
So I’ve managed to source a NOS cap from Cyprus of all places. Just one more little detail ticked off a very long list.
1959 Triumph TR3A 