1-2 NL flush and straight draw all-in call

[gworm]

9 handed, Live game. Hero is in 6th position. 3 players limp to Hero. Hero limps with A-3 hearts. Button limps, small blind limps, big blind bumps to $10. All 3 limpers call, Hero calls, button and small blind call. Flop comes 2-4-7 with two hearts. Big Blind shoves all-in for $90 into the $70 pot. Action folds to hero. Read on big blind is that he would only do this with a pair- he wouldn't c-bet two over cards. Only other read is that the button has been pretty loose and has a monster stack.

P.S. I allready hear the "I wouldn't call pre-flop" argument. More interested in the flop thinking here...