I have the early (99) corvette return style stock rails and stock injectors. There is what appears to be a vacuum reference on what appears to be a rail mounted FPR. I have been told these are fuel rail dampers as well? Anyways I have a manifold referenced vacuum line going to the port on it. Is this correct? Or should there be nothing going to it? When I received the engine it had nothing hooked up to it, it was open to ambient. Thanks

 

Those rails were from the 97-98 vettes only. And yes that is an adjustable fuel pressure regulator. You remove the vac line to set the pressure, then with the vac line attached it will lower the pressure. The pressure will vary dependent on the driving conditions or load.

 

Yes then they are from a 97-98. I just was not sure if it needs to have the vacuum line hooked up to maintain a constant pressure differential across the injector (1:1 regulator) or if it should be unhooked. If the vacuum line is left hooked up then wouldnt the Injector Scaling table be a constant value straight across and not increasing with increased manifold pressure like it shows in the calibration files? The regulator should compensate with the vacuum reference at a 1:1 ratio.

 

The 97-98 Corvette FPR is vented to atmosphere with a vacuum hose to the intake duct just ahead of the TB. Probably less chance of dirt/water getting in the FPR then a foam filter like on an old EGR vacuum regulator solenoid.

Also maybe with a severely restricted air fliter, there could be enough vacuum in the intake duct to lower the fuel pressure to help lean out the AFR.

Russ Kemp