I needed to lower my fuel pressure, since the stock regulator was giving me 52psi, and it should be more like 38 at idle, 46 at WOT. There are two types of regulators for the f-body, some are complete replacement units, but most actually require modification of the stock regulator to add adjustability. This is the variety I used, a billet aluminum unit from Metco.

You'll need to pull the fuel rails off the engine to do this. Disconnect the battery negative cable first. There are four screws that hold the rails down to the manifold, remove these. Disconnect the feed and return fuel lines, using standard fuel disconnect tools available at pretty much any auto parts store for about $5 (picture at left). You'll need the 5/16" and 3/8" sizes, and be prepared with a rag to catch fuel leaking out. Disconnect the electrical connectors on all eight injectors, by pushing the metal clip toward the center of the engine and pulling the connector up. Disconnect the vacuum line that connects to the cap of the regulator. At this point, the rails are only held down by the o-rings on the injectors, so just pull the whole thing straight up and out.

Pull the regulator off the fuel rail, and take a look at the instructions for modifying it. I assume most of the regulators are similar, but I've only done this for the Metco unit. Essentially, you grind around the stock regulator cap to remove it (I used a bench grinder - a Dremel would have taken much longer). Then you replace the cap with the new unit, fastening it down with screws around the edge. The directions that come with the unit ought to have better detail, and I won't repeat them here.

Once that's done, reattach the regulator to the fuel rail, and set the adjuster per the instructions such that it will start up the car at a halfway decent pressure, which you'll adjust later.

Carefully reinstall the fuel rails into the car, making sure the injectors are all positioned correctly before you push the rails down into position. Ensure all the o-rings are still there and correctly situated. Attach the fuel lines, electrical connectors, and tighten down the four rail bolts (not too tight, this is aluminum, probably ~10 ft-lbs or so). Re-connect the battery. 

To adjust the pressure, you'll need a pressure gauge mounted in the fuel line, usually at the schrader valve. With the car running, disconnect the vacuum line that connects to the regulator and check the pressure. Turn the threaded fitting in the cap until your pressure reads 46psi. Re-attach the vacuum line, and ensure that the pressure drops to about 38psi. If it doesn't, the regulator isn't functioning correctly, and you may have assembled it wrong.

You're done!

Conclusions

This isn't a particularly fun modification, and I'd only recommend it if you have some reason to change your pressure. Simply raising or lowering your pressure is unlikely to gain horsepower, I'd be doing it to make better use of your fuel injectors or programming only.

Copyright © 1997-2004 David Mills, no part of this site (http://www.go-fast.org/) may be reproduced without permission of the author. The author makes no claims or guarantees as to the quality of the information on this site. I'm an enthusiast just like you, and while everything here is correct as I know it, I'm not responsible if your car breaks.