Fuel leak

[fredh]

I have a 73P- T337G. I have had the airplane for 7 months with no fuel leaks. I had a bad rear engine and we overhauled it never leaking fuel for 5 months, fuel almost full. We complete the engine test run many times, test fly, bring to avionics shop for some radio work, fly back home, no leaks, total flight time 3-4hrs since new engine. Fly to different airport for fuel, fly 1hr after fill up put in heated hanger, I'm in Michigan, Radiant tube heater over airplane, fuel leaking from both engines, seams like leaking from strainer but possible from above strainer. Turned off fuel selector both stopped leaking. I turned off furnace, aired out hanger for 6 hrs turned on fuel selectors to proper setting and they both leaked again. I thought maybe expanding fuel from heater but it didn't seem to matter. Any idea's?
Fred