actually im using the stock pump and a walboro inline pump, what should the fuel pressure PSI be???

 

i am sure you can find that info on shoebox's site, thanks again shoebox

www.shbox.com

 

At idle, vacuum line off the FPR it should ideally be 43.5psi. GM accepts anything in the 41-47psi range. Reattach the vacuum line, and the pressure should drop proportional to intake manifold vacuum, up to 8psi drop with a stock cam, less with a more aggressive cam. Take it out on the road to max RPM/max engine load and the fuel pressure should hold the pressure it was at without the vacuum line at idle. Anything less than 40psi would be a
problem.

If the PCM injector constant was tuned for a higher injector pressure, you have to run it at that level.