I agree with Tim, either b/f flop or bet/3bet.
A b/f looks very weak, but a bet/3bet is a thin play (we might be in pretty bad shape vs a flush a lot of the time) so even though I would rather 3bet it's also ok to fold imo.
Still, the following is kind of a worst-case-range and we're still not crushed:
Board: Th 8h 4h
Dead:
equity win tie pots won pots tied
Hand 0: 66.940% 66.94% 00.00% 33798 0.00 { TT, 88, 44, AhKh, AhQh, AhJh, Ah9h, Ah7h, Ah6h, Ah5h, Ah3h, Ah2h, KhQh, KhJh, Kh9h, Kh7h, Kh6h, Kh5h, Kh3h, Kh2h, QhJh, Qh9h, Qh7h, Qh6h, Qh5h, Qh3h, Qh2h, Jh9h, Jh7h, Jh6h, Jh5h, 9h7h, 9h6h, 9h5h, 7h6h, 7h5h, 7h3h, 6h3h, 5h3h, 3h2h, AhKc, AhKd, AhKs, AhQc, AhQd, AhQs, AhJc, AhJd, AhJs, Ah9c, Ah9d, Ah9s, Ah7c, Ah7d, Ah7s }
Hand 1: 33.060% 33.06% 00.00% 16692 0.00 { KcKh }
So if he sometimes spazzes out with a TP type hand or even a lower FD we're actually in pretty good shape.
Calling the flopraise brings the problem that we don't know how to continue on the turn.
If we lead out we isolate ourselves against stronger hands (mostly flushes), but if we check and he bets we're not really in a better spot - he might be inclined to check back all FDs and only bet flushes.
So we can still just continue due to odds and outs, mostly we end up check/folding because even our flush-outs aren't clean.
