So - what exactly is a 4180? It looks like a 4160 but with two "normal" boosters and two annular ones. Rebuild kit comes with a two-stage power valve, too.
Any idea how many CFM it's rated for... and if stock, what jetting/metering plate should it have? From the size of the butterflies I would assume at least 500. If so, I may use it on my mild truck 390 project
