[Formulas]

The primary problem nowadays with new mechanical pumps is incorrect pressure, ... To high, ... Some reportedly around 9psi if i remember right, .... You would hope a true blue Carter pump is correct

[Shiny]

That's consistent with my experience and understanding.

If gtobird wants to fully characterize his pump, then agree he needs a flow vs pressure plot across the full range. But as Formulas says, and what I've seen on this forum, the typical concern for a stock carb application is overpressure, which is likely highest with zero flow. The typical concern for a performance application is sufficient flow.

gtobird - What carb are you feeding?

Are you trying to solve a problem or avoid one?

I looked up a bunch of aftermarket mechanical pump listings a while back and found some of the "tall can" pumps are actually "spec'd" (at least listed) to deliver 9 or 10 psi. The "short can" pumps are typically spec'd lower, around 6 psi max. And neither of these "spec" values guarantee that's what you actually get. It wouldn't surprise us to see a pump spec'd 6 psi max delivering 8 or more psi.... which may be why gtobird is trying to avoid a rat-hole ???

Forgive me if I'm wrong, but my notes say a Carter M6122 (tall can) was spec'd at 9 psi max. Carter's short can pumps for similar vintage (M4868, M4690, M4885) were spec'd for 6.5 psi max (again, what I find in my old notes). I have no idea what they actually deliver.

Mike