Discuss stock fuel pressure 1990 Mustang 5.0 on AllFordMustangs.com, the place for Mustang enthusiasts.
Welcome to our Mustang forums where Mustangers come together to hang out, discuss and enjoy their favorite Mustang hobby with fellow Mustang enthusiasts. We invite everyone to read, post, and enjoy our Mustang forum as well as the many other sections of our site.
You are currently viewing our forums as a guest. By joining our community you gain access to post topics, communicate with members, upload your photos and access many other special features. Registration is fast, simple and free so why wait, join our Mustang community today! If you have any problems with registration or your account login, please contact support.
Stock pressure is usually 39 psi. There's times that lower than stock pressure is good, a stock 5.0 tends to run slightly rich so a couple of psi lower would do some good. But the engine will dictate where the right pressure setting should be based on it's needs.
AFM Site Administrator
Member: Mustang Club of America #82740, White Mustang Registry #362, NMRA, Fun Ford Weekend, Mustangs of Burlington MOOG Certified Technician For mods and sound clips, see profile and gallery.
As Eagle said, lowering the pressure will lean out the mixture. It's just like putting smaller jets in a carb. Also, I agree that there are times to run lower than the spec'd pressure. For instance, my car has a Cobra intake and E303 cam, Edelbrock heads, etc. All the emission systems in place and working. Where I live, we must pass an annual emission inspection. For pre-96 cars, that's a visual for cats and a tailpipe sniffer check. My car won't pass with the tune set up that I normally run. Excess HC. To pass, I retard the timing back to the stock 10 degrees and reduce the fuel pressure to 34 - 35 from the 40 I normally run. Reducing the pressure leans the motor just enough to pass.
Craigfield, Tennessee Member Music City Mustang Club '93 LX Mustang '56 Ford Thunderbird convert '06 Harley Street Glide '01 Harley Softail Custom