Fuel pressure is an important ingredient for proper operation of the carburetors on the MG. Too little pressure, and the engine will starve for fuel at high power operation. To much pressure, and the carburetor float chambers will likely overflow. The SU carburetors work well with fuel pressure in the range of 1.5 psi to 3.5 psi at the inlet to the float chamber. Pressure of 5 psi or higher will likely make the fuel overflow. The original SU electric fuel pump has an internal spring on the operating solenoid that effectively limits pressure to the intended range.

Some aftermarket fuel pumps may have higher pressure output, which could cause problems. For this case you may need to install a pressure regulator in line after the fuel pump.

For some competition applications it may be desireable to install a fuel pump with higher pressure output, and also install a fuel pressure regulator in the fuel line close to the carburetors. This arrangement can help to assure a reliable flow of fuel at the carburetors with no worry about pressure loss in the feed line between the fuel pump and the carburetorss at high flow rates.

At 06:12 PM 12/20/2002 -0600, M. Edwin Vaughan wrote:
"I am looking for a source (other than VB) for a fuel pressure regulator."

Any local speed shop should sell you the same Purolator pressure regulator for about half the price (or less). On line you can go here:
www.racerpartswholesale.com
Click on "Complete Catalog Index", then click on "Purolator Products".
Find: Part No. PRO55.

If that doesn't work, try the Google search engine, as the same part is sold by many vendors (under different part numbers). I have often seen this part selling for under $15 (sometimes for less than $10).

Some racing friends have reported a small problem with this particular regulator. Apparently if the car is left to sit unused for an extended period of time the Purolator regulator may sieze or stick internally, which may cause stoppage of fuel flow. The immediate fix for this problem is to turn the pressure adjustment to maximum to use internal spring force to break the relief valve loose, and then to minimum to allow the spring to relax, and then set it to the desired pressure. I have personally used this device for a few years (not recently) on my regularly driven street car and have never experienced this problem (YMMV). If this idea bothers you, there are more expensive fuel pressure regulators available which most likely would not have this problem. Consult you favorite speed shop for recommendations.

The same regulator (made by Arvinmeritor) is privately labeled for Purolator, NAPA, Spectre and others. They are all the same. For the Purolator and NAPA brand parts made during Nov 2001 through August 2002 there was a recall due to the diaphragm not being fuel compatible.

Here is another article about comparison and installation of a Holly fuel pressure regulator.