Valve Springs

Hi All
After sorting a fuel starvation problem on my 1st run last sunday ,i set off again, ran fine for a few miles so started a return to base ,pulled into drive and she cut out ,a quick push and nothing ,up on ramp to find exhaust valves (yes both) stuck in the open position . So a strip down reveals both exhaust valve springs to be shorter than the inlet ! Im sure this cant be correct ? can anybody point me in the right direction to order some new ones ? And length etc .I have the sopwith rockers so might make a difference on tension .And think to replace the inlet ones as well .(new valve guides being made with more tolerance ).

Thanks for your help in advance 

what history do you know about your springs, i had two set made at a firm  advetising in the vmcc journal, they both collapsed very quickly, i comlpained had some replacments and they did the same, i put the old ones back in. I have some made by terrys in now they are ok but bradshaw commented about vavle springs getting too hot and collapsing. the other thing i suppose is how
hot is your engine getting

Thanks Keith , interesting that valve failures are noted , I don't know if the engine is getting too hot it was only a short run out but could be , you mention 'terrys ' for springs , I will look them up if that's the name of the company? 

cheers Tony 

the ones i had were from a batch david hales had made sometime ago they have all been used know, i think they were specially made and i dont know if terrys still exist

Ok Keith thanks