Learn English – Feel like doing something

“Let’s make like a bakery truck and haul buns” is jokingly said when one wants to leave a party. Our buns (buttocks) are compared to a bakery truck, that is, they are as heavy and big as a bakery truck which hauls (drags) heavily.

On the other hand a bakery truck also sells buns (small, sometimes sweet breads) having a shape that resembles to a curvy contour of a girls gluteus maximus muscles as seen from behind: "Margie's buns look nice and tight now that she's working out.”

In other words buns sold by the bakery truck are compared to the slang word of ass, cheeks, buttocks. There is a pun which mixes our buns with the buns sold by a bakery truck.

As a result we can understand the pun this way: “let’s move our asses out of here” or “let’s get out of here”.

“Let’s blow this clambake” it’s a very silly way to say “Let’s get a move on”, where blow is the slang word for “ to go, leave, exit” or “leave this less than an interesting place”.

In very generalized terms, it means:

If you meet the stated requirements, I will let you proceed. If you clearly do not meet the stated requirements and are attempting to convince me that I should let you proceed anyway, I will force you to leave.

Most commonly, the "stated requirements" are "can you pay the amount I am demanding", i.e. "do you have enough money". For a literal application of the phrase, consider a couple of poor college students trying to get into a party for which there is a $25 entrance fee. If they show up without enough money, and instead of paying they attempt to convince the gatekeeper that they are friends of the band, he might well tell them "Money talks, BS walks" as he refuses them entry.