Fuel Filters & Pressure Regulators updated by FB 09.09.04

The need to regulate fuel pressure on carburettor cars

1) The SU carburettor in particular does not need high fuel pressures, indeed too HIGH a fuel pressure could force open the needle valve in the carburettor (held shut ONLY by the float pressure) leading to flooding/over rich fuelling, as too much fuel gets into the float chamber (to escape out of the jet hole and/or the overflow)

.. I personally consider more than maybe 2psi is probably excessive for an SU carburettor, maybe 3psi if the carburettor is fitted with a new higher performance VITON needle valve, maybe less if it has a worn DELRIN valve? .....if you get fuel overflow flooding with your new pump consider using a pressure regulator.

2) What SU equipped engines need is enough VOLUME to deal with the requirements of a tuned lump NO MORE pressure than standard!

The combination of low pressure and large volume needs to be arrived at via the use of a high performance (higher volume AND pressure) pump that can deliver the volume AND a pressure regulator that can limit the pressure that larger VOLUME can bedelivered at....

High psi fuel injection pumps for use on carburettored are TOTAL overkill and you increase the fire risk with a leak from a high pressure fuel line, you also over stress the fuel lines and fittings, indeed exposure of bare skin to escaping high pressure liquids can be dangerous in itself!

Location

1) In the engine bay

Pros: VERY easy to access, easier to fit, you can easily see if they are full or if fuel is pumping

Cons: near all the hot stuff!!! Leaks might catch fire!!! proximity of HOT THINGS

2) under the rear subframe

Pros: Out of harms way / leaks fall on road or worst on exhaust

Cons: get dirty/corroded/potential for unseen damage/malfunction

3) In the boot

Pros: PRETTY easy to access

Cons: might get disturbed/damaged by day-to-day doings unless boxed in or protected

GENERALLY

THESE MUST be well secured away from rotating/sharp/hot things if you can get it right put it in the engine bay

PRESSURE REGULATORS

IF YOU CHANGE THE FUEL PUMP TO AN UPRATED ONE you might only need a pressure regulator without a guage unless you are showing off or uncertain of the accuracy of the pressure regulator

They Are best located near the carbs HOWEVER think carefully about fitting a high pressure pump to a carburettored car, you DON'T need pressure you need VOLUME so 10PSI into an SU is TOO MUCH you only need 2-3 psi as far as I understand it otherwise the needle valve blows out of the float bowl and you get flooding ... go for a low pressure high volume pump with TUNED engines running SUs or WEBERS

AND

IMAGINE YOUR NIGHTMARE.... a punctured fuel line... oh how petrol at 50psi sprays compared with only 5psi!!!!

REGULATOR / FILTER TYPES

1) GLASS / METAL

FILTERS though fragile in reation to plastic/metal to impact damage are less likely to melt than plastic and are easier to see through

DITTO glass bowled pressure regulators

PLASTIC - NOT APPLICABLE to PRESSURE REGULATORS

Cheap, less likely to leak if impacted MORE likely to leak if exposed to HEAT

PRESSURE GAUGE & REGULATOR + FILTER

Filters with built in pressure regulators and/or fuel pressure gauges are overkill unless you are uprating your pump or suspect a failure

MY LEARNED RECOMMENDATION

REGULATOR:

Bulkhead mounting: MALPASSI FILTER KING

In-line: PUROLATOR dial pressure regulator

FILTER: A well secured PUROLATOR glass and metal in line filter

PRESSURE REG & FILTER? bulkhead mounted Malpassi Filter King with glass bowl and pressure gauge

TAKE GREAT CARE WHEN FITTING FUEL LINE ACCESSORIES IF IN ANY DOUBT SEEK PROFESSIONAL ADVICE YOUR LIFE AND CAR RELY ON GETTING IT 100%