I have a Mallory 140 pump.their web site says I must run a return at least 3/8 back to the tank.iused to have it dead headed and it worked ok as long as the engine was runnin.Anyhoo, now with it hooked up like their instr. when im going down the road and push on the gas my pressure goes down.if I keep accelerating it will go to zero.will it hurt anything just to keep dead headed.when it was deadheaded it was a little noisy but with the return its very quite

never bypassed a 140

When running it with a bypass, they have a solid spacer you put where the bypass spring inside the pump goes

they told me to just take the spring out and snug the set screw against the little solid rod that's in there.i cant seem to get a hold of any one,ill just put the spring back in but im not shure of the adjustment.they had the instr. on their website but now I can seem to find them.

Never knew a 140 to be anything but deadheaded............I bypassed the Aeromotive hot-rod pump and same thing, pressure drops and didn`t pull well from the 1/8th mi. on......Get a Magnafuel 300 and be done w/it..........

Due to vapor locking issues....I recently swapped from a deadheaded setup to a bypass with a 140. Unreal the reduction in noise from the pump and regulator....

I didn't do anything to the pump? Don't have a fulltime gauge on it, but it seems to work fine. Im running same size feed and return, -8. RobbMc used to work for Mallory and told me (and plenty others) that your return is supposed to be one size bigger than feed.

I run a 140 pump with bypass spacer and a 4309 bypass regulator. -8 feed line and -8 return line to cell. Rock solid pressure. If deadheading, should use a spring in pump and deadhead style reg

http://static.summitracing.com/global/im...urnstyle430.pdf 4309 bypass reg. shows bypass spacer vs. spring info

http://static.summitracing.com/global/im...10_140_0003.pdf

Learn sumptin new everyday...........

that's what im missin is the spacer.Dosnt look like to big a deal to make one.

Should be easy.. screw in the by pass plug..
see how much material on the screw you have.. make
it long enough to get the nut on... based on the
pic it looks fairly short.. like a 1/4" to 3/8"

Worst advise ever. Lol

Did a little reading...and based on what i read,fwiw... there is no reason to use the spacer. Gonna track down Robb and see what he says
..

FWIW Mallory 140's used to be sold 2 different ways. Some were sold regulated down to about 6psi - others were sold with a by-pass regulator in the box - those pumps would dead-head about 18psi. I have used both, with pros and cons to each. The by-pass regulator is nice because the fuel to the carbs does not go through the needle/seat in the regulator - the by-pass fuel does.

I ran a comp 140 pump for years both bypassed and non bypassed and yes it made a lot less noise when bypassed,I ran a -08 line to the carb fuel log and then bypassed after to bleed off un needed fuel and ran a -08 line back to the tank, don't make the mistake of using a smaller return line as you probably won't be able to adjust the pressure down far enough because of back pressure from the smaller line. damhik

Come on Ray go easy on me and I stepped out of the "toy" pumps years ago and went FASTER........

You were about the only one...

I used a bypassed 140 as well. Like has been stated make the return big. Low pressure was never an issue. Too much was another story.
Doug