Fuel Pressure Regulator Vacuum Boost Port Hookup

[65coupei6]

I just installed a Mallory 4309 regulator to my Holley 7448 350cfm carb. Should I hook up the vacuum/boost port on the regulator or leave it open :

Here are the instructions from Mallory:

VACUUM/BOOST COMPENSATION PORT
While it is not necessary to connect a hose to the
vacuum/boost compensation port, it may be beneficial
in some cases. The vacuum/boost compensation
port can be used to momentarily decrease fuel
pressure (vacuum compensation) at idle and part
throttle, or increase fuel pressure under blower boost
(boost compensation). Connect a hose between the
vacuum/boost compensation port and a carburetor
or intake manifold vacuum port to vacuum index the
regulator. The set pressure of the regulator decreases
about 1 PSI for every 2 inches Hg (2 inches on
the vacuum gauge). Connect a hose between the
vacuum/boost compensation port and an intake
manifold boost port to boost index the regulator. The
set pressure of the regulator increases 1 PSI for
every 1 PSI of boost.
NOTE: DONOT exceed the fuel pump manufacturer’s maximum
recommended operating pressures. This could damage
the fuel pump.

 

[Junk-Falcon]

from reading it looks like its for a blower? you got one of them hookedup?if so i would thinkso but im bettin it realy only would work worth a crap if you got a elc pump ,, a ford pump only puts out from 3 to 6psi

 

[65coupei6]

I do have an electric pump that is putting out 6 psi. No blower or turbo.

 

[Junk-Falcon]

the only thing that would realy be needed for is if when you runing it hard it is running out of gas

i dont think you will realy need it

and i dont think it would work to do anything coz theres no boost in the intake so it would only see vac to none ,, but no boost ,, so it wont chang it

 

[addo]

Modern cars have this feature. It's simple, and free to hook up. If it makes the car run worse when fitted, unhook it.

 

[65ShelbyClone]

A regulator referenced to manifold pressure is necessary with EFI in order to keep the pressure differential injector inlet and outlet constant. Blowthrough carbs need it for a similar reason. Not so with a normally aspirated carb; they only need a constant pressure. If the fuel pressure drops at high load, then something in the fuel system is not flowing enough.

 

[powerband]

Simple vacuum needle valve usually larger lines and return cutout are integral to it's operstion as noted. Simple mechanical inexpensive part can wreak havoc on computer engine controls..

( Error codes 3 thru 337 :roll: )

Is the Mallory regulator calibrated or adjustable?. I had a Mr. Gasket fuel regulator rupture the diaphragm and pump gas over the engine till I shut it down. Pretty scary...

Not familiar with Turbo requirements but experimented with 350 CFM 2300's . On the 170 the 350 Holley 2bbl worked well but my eyes watered from the unburned gas at other than WOT. On the built 250 the 350 was smooth and powerful. I used it on OFFY manifold with outer carbs blocked. I believe it would outperform the 3X1 Holleys until maximum flow (redline ?) advantage of outer carbs at intake ports. 'Picked up a 4412 - 500 CFM version to try...

'Picked up a 5412 500 CFM version to try...

I suggest adding a guage to the line near the carb. I was surprised that as the RPM went up the output of the mechanical pump leveled off or fell as the fuel demand also rose (?) . @4-5 lbs at idle seemed high but at accel went to 3- 4 with 3 Holley 1904's 185/215/185 CFM progressive. I installed regulator because popular info on 5200 H/W says the float needles don't tolerate fluctuating pressure.