I am using an external aeromotive regulator with fabbed up rails and a sumped tank and external pump. I had all the fuel system out to weld in the cage and sfc's and just could'nt bring myself to put plastic fuel lines back.
Stock motor and injectors for now, I just need to be able to crank and move the car around.

What is the base fuel pressure on a stock LT1? Is it set with the vaccum line hooked up or not? How much should the pressure rise/fall under load or vaccum? Thanks in advance. James

 

The fuel pressure, measured without the vacuum line connected, should be 43.5psi. When you reconnect the vacuum line, the fuel pressure will drop in proportion to the intake manifold vacuum.... maybe as much as 8psi drop with a stock cam, a lot less with a radical cam.

 

Oops! I checked my fuel PSI on my new 383 with the vacuum line connected, and it read ~43psi, so I figured it was fine. So you're telling me that my fuel pressure is actually higher?

What should it be on a 383 w/ 42# injectors and a Racetronix fuel pump (Walbro) & harness, the same 43.5psi?

Edit: I have a cc306 cam and LE2 heads

 

A "vacuum compensated" fuel pressure regulator controls the "differential pressure" across the injector, NOT the rail pressure. You want the rail pressure to equal 43.5psi minus the intake manifold vacuum. You accomplish this by setting the fuel pressure to 43.5psi, WITHOUT the vacuum connected.
What did you tell your programmer about the injectors and fuel pressure setting? In order to program for your setup, he had to know the brand of the injectors, the flow rating of the injectors, and the pressure you planned to run the fuel system at. Normally, you fill that info in the programmer's questionaire. If he didn't ask you what fuel pressure you were running, he PROBABLY assumed you were running at 43.5psi. Check with your programmer.

 

Thanks Injuneer

 

Bryan Herter of PCMForLess tuned it. He did not mention anything about fuel pressure, but I did tell him the info on my injectors and fuel pump, etc. I checked the fuel pressure last night, and it was at 50psi!! without the vacuum on the regulator. I tuned that down to ~43.5, and the car ran very well. I will check with Bryan just to make sure the psi is right.