Mechanical fuel pump modification


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By slumlord444 - 11 Years Ago
I have a factory dual action mechanical fuel pump on my '57 T-Bird. I run an electric pump in addition to the mechanical pump mounted by the gas tank. My concern has been that if the diaphragm in the mechanical pump fails there is a possibility of a lot of gas going into the oil pan which is a bad thing. Is it possible to modify the pump with a bypass tube through the pump to avoid this possibility and still leave the vacuum pump assist part for the wipers working? I could just take the pump apart and play with it but no use reinventing the wheel if someone has already done it. Back in my serious drag racing days I just eliminated the stock pump totally and put a block off plate where the pump went. Worked fine but wipers were less than ideal. Could do that and go with electric wipers but not crazy about that. Sort of want to keep it looking stock but not be stock. That is sort of a thing with me.   
By Ted - 11 Years Ago

Sounds like you simply need to make a dummy banjo fitting that will allow the fuel to bypass the pump internals completely.  If you simply use only one of the existing ports to support the new fitting, I doubt anyone is going to notice only one port being used.  And if they do notice, not a big deal.
By 2721955meteor - 11 Years Ago
have electric on ranchero,just for long storage ,to eliminate long cranking.it is activated by a push buton so would only be used short birsts.meckanical pump sucks threw the electric and elect is close to tank. have made this conversion on several tbirds verry helpful with tpot carbs. the question of fuel delusion re failed meckanical diaphram is posible.so useing bothe is not wise
By slumlord444 - 11 Years Ago
I have the electric pump for two reasons. The dual quads tend to run out of fuel if it sits for a while. Second reason is that the stock mechanical pump could not keep up with the dual quads. Best bet may be to leave the stock pump in place to provide vacuum assist to the wipers and bypass it totally for the gas supply. A plus to this is that when I am going to let it sit for a while I can turn off the electric pump and let the carbs run dry. No chance for gas to leak into the crankcase and no fuel in the carbs to gum up and cause problems with the crap gas we have today. 
By slumlord444 - 10 Years Ago
I finally got around to taking the fuel pump apart. This was actually fairly simple once I got it apart. I removed the pivot pin for the pump arm and the diaphragm for the fuel side fell out. Removed the two check valves in the bottom of the fuel side of the pump which leaves an empty lower pump housing. Cut the center out of the fuel diaphragm. Used it for one gasket and as a pattern for a second gasket and a thin metal block off plate. Re installed the block off plate with a gasket on both sides where the diaphragm was. This seals off the fuel part so no fuel can possibly get in the crankcase and leaves the lower half of the pump as an empty chamber for fuel to simply pass through. The second diaphragm for the vacuum assist for the windshield wipers is left in tact and working. Simple. Looks stock. Still have vacuum assist for the wipers and if you don't know where the switch for the electric pump is hidden under the dash, no one is going far with the car. Now I am wondering that if I have a problem with low vacuum with my new cam  causing a problem with the power brakes if I can tap in to the outlet side of the vacuum from the fuel pump for vacuum to the power brakes?  
By Ted - 10 Years Ago
slumlord444 (3/29/2015)

.....Now I am wondering that if I have a problem with low vacuum with my new cam  causing a problem with the power brakes if I can tap in to the outlet side of the vacuum from the fuel pump for vacuum to the power brakes?

That’s a No for hooking up the vacuum assist pump on top of the fuel pump to the power brakes.  You’ll either need a vacuum can with check valves to store the engine generated vacuum or a separate vacuum pump for the amount of vacuum required for power brakes.  Vacuum pumps from diesel engine applications work well for power brakes.  They come in either electric or mechanical versions.
By DryLakesRacer - 10 Years Ago
Dual quad guys, remember the fuel line is a 5/16" and is a contributing factor in the lack of fuel. An electric pump definatly helps but is not a cure all. Even tho we pick on them the 270's and fuel injected 57's had 3/8" fuel feed lines. I am not sure what Ford did for the " E & F" Birds and full size 57's. Our stock fuel pumps also use 1/4" pipe fittings which are also a restriction.
By slumlord444 - 10 Years Ago
I definitely have a concern with the fuel line size. Have any of you guys with 350 to 450+ horsepower engines had to go to bigger fuel lines? As I stared in the first post, I had fuel problems with the stock engine when I first installed the factory dual quads back in 1966. It literally ran out of gas and shut down when I hit third gear. Added an electric pump in addition to the mechanical pump and the problem was fixed. When I built the first race motor back in 1968 I kept the electric pump removed the mechanical pump. No fuel problems. With the new rebuild I hope to be pulling 400 horsepower + or -. I am thinking this may be a problem. The factory high performance Fords in the 1960's used larger fuel lines as I recall. I will find out for sure once I get it running and all sorted out.