The Stovebolt Site Forums The Shop Area Engine Shop Rochester B Flooding Issue

I am having a flooding problem ...
Rochester Model B flooding after only changing mechanical fuel pump (classicpart.com) which looks like-for-like for what i pulled off. It for sure has better flow and pressure.
The only way i know is that it is keeping inline filter full where the old pump was not.
I have stripped the carb, cleaned and re-assy. No change.
Float level looks pretty close. Slightly over 1-9/32" when air horn upside down. When i blow thru it the needle holds ... by mouth, not compressed air. So i think seat is reasonable.

But ... i do not know how to measure the pressure the pump is putting to the carb. Do i need an inline gauge or something?

When you did the vacuum pump test ... was vacuum pump connected to fuel inlet on the air horn? that is similar ... but more refined than me blowing on the fuel inlet right?

i have not replace the float needle and seat .... that might be what is needed. Was good enough for the low pressure from the worn fuel pump but not good enough for better / correct pressure.

A combination fuel pressure / vacuum gauge can be purchased at any chain auto parts store for $20. Disconnect the fuel line from the carburetor and attach the fuel pressure gauge with a "T" to the fuel line and carburetor and crank/run the engine. The fuel pressure should be 2-4 psi. My truck runs at 2.5psi.

Don't pay any attention to the fuel inside clear, inline fuel filters. Some run normally full of fuel, some run at full throttle with nearly no visible fuel in them at all, and some look like a coffee pot percolator with fuel spurting and bubbling.

thanks ... got the gauge ... yep. >9psi to the carb
is it bad idea to put regulator before the carb?
I though Classic Parts was safe place to get parts. I even ask for pressure and flow rate before i bought it but they said they had no info on it. I should have known from that comment. I went to NAPA and saw the one they have in stock ... looks the same and feels the same force to operate the pump lever.
How do i find one set up for 2-4 psi?

smsvo, This pump from RockAuto, Carter M751 is rated for 4 psi output, and would work on a 1951 216 or 235. Head over to RockAuto and search under your year and engine and it should come up with some options. If you want to buy locally, get the part #'s from RockAuto that have the correct specs and ask for that at your parts store.

The output pressure of a mechanical fuel pump is determined by the strength of the spring that is incorporated into the linkage. The camshaft lobe moves the diaphragm and creates the suction that the pump develops- - - -the spring pushes the diaphragm down as the cam lobe releases the lift, and the stronger the spring, the higher the deadhead pressure against the needle valve in the carburetor will be. A rebuilder such as "Then and Now" knows this, and they will install the correct spring for the application. A good pressure regulator between the pump and the carb will bypass part of the fuel flow back to the inlet side of the pump and control pressure that way.
Jerry

If it were me, I would take the spring out of the old pump and put it in the new pump and test test what pressure the new pump puts out.
(I hate returning parts. That's just me I guess.)

thanks
i am working on 1959 chevy pickup 235 ... so looks like Carter M2999
and a fraction of the price i paid at classic parts ...

Isn't the base on that thicker than the original, requiring slightly longer (1/4" longer) bolts to attach it? That's what I'm going through right now with my 1958. The one that I've seen at Jim Carter and some other sites with the thinner base have the wrong orientation for the inlet and outlet (180 degrees) for my fuel lines (120 degrees).

9 lbs is way too much and would account for the flooding. I would buy one from Rock Auto and return the one from Classic Parts. They do have a good return policy so that is what I would be doing.