accelerator pump

Well this is why I ask questions.
Just found photo of a BBd with the
2379 casting number...
As a side
I posted a question on another site and the first reply was "why do you want to know". Man has way to much time on his hands. Sometimes fast to ask a question then to try and find the answer In the above case another man gave a partial
correct answer. Again I found a site with the most correct answers...