The B.B. in the title represents that this is from the archive of the late Bill Bently, who ran a flathead Q&A informational site before he passed away. All threads from this source will be titled using the B.B. identifier on this site. We’re archiving some of the threads, so that his work is not lost or forgotten and so they will continue to educate flathead enthusiasts for years to come.
To all fuel pump push rod welders. 1932-1948 models
Many years of Flathead experience taught me that the fuel Pump push rod DOES NOT wear down causing pump operation problems. It does wear but how much would be realistic? .. maybe 1/16″ to 3/32″ for 100,000 miles?, Ive measured them and its not much more than this.
What does wear then?. It’s the fuel pump lever/link system!. Most are a laminated riveted plate style with a very small pressure bearing surface which wears very quickly especially as many owners fitted new units without lubing the linkage. Bolt it on!, she’ll be right mate!. We fitted hundreds of fuel pump kits so you get to know them very well.
OK, the linkage wears & the pump cant deliver the 1 1/2 lbs minimum required, so the owner [or the mechanic] then builds up the rod by brazing or welding an amount that is guessed [or measured] & bolts it altogether again & it works fine—must be the right thing to do cos the pump in hand when checked worked fine!, just not enough rod length right?, problem fixed?, not quite!.
If the rod travel was not carefully measured & its now too long, the pump mount will accommodate this by bending & or cracking near the stud holes. How hard is it to find a pump mount that isn’t bowed or cracked?—very!. We probably had in stock 30-40 units & if you found one that was straight it would most likely have a stripped thread or the guide tube was missing etc!.
[49-54 mounts were beefed up in this area so usually the pump linkage bent & the diaphragm stretched some & the camshaft eccentric suffered too!]
When that pump finally wears out, [after the rod has probably been brazed up once more] a new pump is bolted straight on without checking pump travel, the mount now really has to bow or break & they did. A result of this bow was a big gap between manifold & pump base causing a very oily engine. The little skinny gasket supplied for the base was replaced by a fat homemade job to try to stem the flow!.
The correct fix for pump linkage wear is a cup or flat washer fixed to the pump lever. Better still a new pump with a proper lever system instead of the Mickey Mouse design that caused the problem in the first place. Sometimes I would replace the linkage on a new pump with a used preferred design. Sorry I cant remember the brand with the solid pivot stop lever design.
I remember now that for my own 35 Sedan I once made up an adjustable push
rod for a special application.
A 1/4″ NF nut was welded to a shortened rod, so the end was hollow, the
bolt’s head was rounded off and a lock nut secured it in place. This would
be a good aftermarket replacement item I reckon.
If your pump mount is bowed get it straightened or find another, don’t file it flat as that will disrupt the recess for the baffle tube & the mount will bow again or the legs will crack or break off. When all is flat that skinny gasket does the job fine. Would Dennis Carpenter or others have new mounts?
[part # 48-9415]
The correct rod spacer/length for your pump will be determined by turning the motor till the rod is at the crest, popping the pump/mount assy on top, pushing down hard & making sure the mount just sits flat on the manifold without “floating” above it, if it floats you’re going to bend it!. Check several times to make sure you have the rod in the socket.
Kiwi Brian
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