I picked up a used VS57 unit yesterday for my 331 stroker build and I'm still a bit confused on the fuel pump issue. In looking at some schematics in PDF fles for the original VS57 set-ups, it shows an electrical and mechanical fuel pump. In talking to others, I'm told that all you need to use is a mechanical fuel pump with a drilled and tapped hole in the top of the pump (in the correct location) to run a vacuum line from the pump to the S/C unit. Can someone explain the method they use for providing more fuel at higher RPM's and less fuel at lower RPM's?

Thanks,

Rono.

  Ron Lane,  Meridian, ID

Let’s see if I can make this sound simple.

 

Running a separate line from the carb hat to the fuel pump diaphragm allows the pump to sense the amount of boost pressure being supplied at the carb.  This makes the fuel pump 'boost referenced'.  In essence, if the fuel pump is putting out 6 psi pressure under normal circumstances, then by being boost referenced it will maintain this 6 psi fuel pressure over the amount of boost being supplied.  Under normal driving conditions where no boost is being generated, then fuel pressure is normal at 6 psi.  As the throttle opening is increased, then boost pressure goes up and the fuel pump automatically senses the amount of boost over atmospheric and maintains the 6 psi fuel pump pressure above the amount of boost being supplied.

 

Stated differently, if the boost pressure at the carb is 6½ psi, then the fuel pump will be putting out 12½ psi assuming the fuel pump delivers 6 psi at atmospheric.  The 6½ psi boost pressure at the carb is also being seen at the fuel pump diaphragm by use of the connecting line and the fuel pump automatically puts out its normal 6 psi above this.  If the pump is not ‘boost referenced’, then the pump is putting out only 6 psi all the time which is in essence a ½ psi short of being able to keep up with the fuel needs of the carb when pressure at the hat is 6½ psi.

Lorena, Texas (South of Waco)

Ted;

Thanks for your reponse. I understand the principle, but I'm still confused on the mechanics (sorry). First, can you give me a year or model fuel pump you would modify? I have heard that the earlier fuel pumps with the vacuum ports on top won't work because they are not located in the correct place. Also, when you say that the line would run to the "carb hat", where would that be on a 4bbl? I haven't decided on a particular 4bbl yet, (*any suggestins) but Iknow that most of them will have a vacuum port for the dizzy avance and another or the PCV valve.

The VS-57 unit I bought was set-up for a Kaiser 226 and came with the carb and pressure box that sill had the selenoid atached to the linkage. Can I use this selenoid on a 4bbl set-up as the secondaries kick in?

Thanks again.

Rono.

  Ron Lane,  Meridian, ID

the line that he is referencing to is to be plugged in anywhere before the carb. like in the intake piping from the blower to the carb hat.

What about the hose fitting on the blower housing? I thought that was what it was for. Takes pressure direct at the source. Chuck in NH

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

A fuel pump for a 390/427/428 Ford FE would be a good place to start.  Preferably a pump that can be taken apart and a pump with the larger inlet/outlet fuel ports.  The 427/428 CJ pumps are already a higher volume rated pump so these would be ideal to start with. 

 

As Eric and Chuck both mention, the pressure pickup for ‘boost referencing’ can be taken anywhere after the blower discharge exit, not just at the carb ‘hat’.  Here are some pics of carb hats with some having the boost reference line located at the hat and others at some point before that.

 

 

 

 

Lorena, Texas (South of Waco)

Ted;

THANKS!! A picture (or 2 or 3) is worth a thousand words. Thanks also for the fuel pump recommendations.

Rono.

  Ron Lane,  Meridian, ID

Rono:

One other thing.  I have found two rebuilt fuel pumps with no diaphragm stem seal.  Without that seal, it is impossible to pressurize the back side of the diaphragm.  So now I always check my pressurized pumps with shop air and a regulator to make sure they can contain at least blower boost pressure.  Moonshadow had one a few years ago at Columbus that couldn't be pressurized, caused him all kinds of headaches.  I believe it was an FE pump.  Chuck?

John - "The Hoosier Hurricane"

You are right John! It was a 427 HiPo pump from Holley. Never did cure it, replaced it! Now I run an inline electric pump with a switch on the dash. I turn it on only when making a "hard" run. Eliminated any sign of starvation. Chuck

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Chuck;

I run a Holly Red Top electric fuel pump in my Customline now. Is this the type of pump you had set-up with a switch for hard runs? Also, what ype of pressure does your mechanical pump put out? I'm still trying t figure out the right type of pump (single or dual diaphram). Do you use one of those overflow fuel filters that sends extra fuel back to the tank? I know...ls of questions

Thanks,

Rono.

  Ron Lane,  Meridian, ID