The Stovebolt Site Forums The Shop Area Engine Shop Fuel Pumps: Riveted Arm or Shaped Arm?

The 235 fuel pumps ride on the cam, with no push rod. However both styles of fuel pump arms are spec'd for the 235. So the arm that's 3 pieces riveted together is intended to ride on the cam? Looks like it would just be digging grooves into the cam surface. Can you really use a riveted arm on a cam just as well as the shaped/single piece arms?

The more important question should be, "When and where was the fuel pump made?"

If you're comparing two new pumps, don't. They're all junk from China and will not function properly regardless of the arm style.

Look for an original pump or a replacement pump built or re-manned before 1990. Have it rebuilt by Then and Now Automotive.

My 216 uses the 3 piece riveted arm.

I should point out that one of the new pumps I installed on the engine failed in about 300 miles. Upon inspection it could be seen that the three metal arms were not riveted together properly and only one of the 1/16th" pieces was actually contacting the cam. I dug out the original pump and rebuilt it over 6000 miles ago.

Concur on the state of replacement parts. My son's 1973 SAAB Sonett still has the original coil and condenser and runs great. My '49 3600 has been through three replacement coils in the last 2 years.

But to the original question: it's fine to have that style arm riding on the cam?

As long as the multi-piece arm contacts the cam across the full width of the face, no problem. I'd use a little Prussian Blue indicator dye to check the cam contact footprint, and correct it with a fine grit belt sander if necessary. Are you smarter that the 12 year old slave laborer who put the pump together in some third world sweatshop?
Jerry

As HRL said, make sure the 3 riveted pieces are in alignment. You can see the wear mark on the cam and pump arm. Only one of the pieces was able to contact the cam. This was a new pump (gold top) that lasted a few hundred miles. It's replacement (silver top) didn't work at all from the get go.

Very instructive guys! Thanks for all that.

I've also noticed that replacement fuel pumps very greatly in the force required to actuate them, like one pump will be 5X as stiff as the next (both new), felt like 60-80lbs of force needed to move the lever. Any guidance on what a reasonable level of force should be to move the arm?

The pressure a pump produces depends on the strength of the return spring. The cam lobe simply creates the suction to pull the gas from the tank to the pump- - - -the tension of the spring determines the fuel pressure the carburetor sees. Those super-stiff springs some manufacturers use will overpower the needle valve in the carburetor by developing 10 PSI or more of fuel pressure, instead ot the 2-5 PSI the carb is desined to get. That's why doing a pressure and vacuum test on the newly installed pump isn't just a good idea- - - -it's something I do just about all the time!
Jerry