I am in the process of putting a 125 hp nitrous system in my 68 Chevelle. The car is primarily a show car, so I am trying to run solid lines for the whole fuel system. I have most of the lines in place, but have a few questions. I ran a dedicated line for the NOS with a Holley Blue pump and 3/8 line. The NOS system expects a 1/4 line from the regulator to the solenoid. I was told I need to drop the fuel pressure to 4 1/2 lbs to offset the 3/8 line. I was also told this is the lowest you want to go with the regulator (reg came with the pump). This sounds correct to me, I just want to be sure. I was also told at the lower pressure the regulator will have trouble keeping a stable fuel flow because the pump is pumping at 14 or so lbs. Is this also true? Finally, I was told I could use the spring out of a red pump, which would in effect lower the output of the blue pump. This would help to stabilize the fuel flow because of the lower pressure. Any opinions would be appreciated.

I would reccomend energizing the pump only when anticipating nitrous use. Also retain the original spring to keep the GPH at its highest.Ussually pressure fluctuation occurs at initial engagement due to the regulator is not moving fuel.when the selonoid is energized the regulator pressure will drop 1/2 psi or more. To avoid this a by-pass system is needed,I think 4.5 psi may be to lean I would start at 6 psi