I am going to be installing 42# Racetronix injectors in my 95 LT1. I have tunercats. What do I need to modify? What constants should I use? FP is about 38-40 psi @ idle.

Part Number Delphi 01D030B (Lucas old 5208009, Lucas New 621031, Delphi old D3181AA)
Static Flow Rate: 42.29 lb/hr @ 43.5PSI (300kPa) or 320gm/min
Static Flow Rate: 48.83 lb/hr @ 58.0PSI (300kPa) or 370gm/min
Dynamic Flow Rate: 9.96 gm/pulse - 2.5ms pulse width and 10ms repetition rate @ 43.5PSI
Coil Resistance: 15.9 Ohms / High Impedance / High-Z (No ECM driver modifications required)

 

I would basically change the injector constant to 42, assuming the FP is 43-44 PSI with no vacuum applied to the FP regulator.

If you have a wideband you can fine tune the results of this major change by adjusting the injector offsets (affects mainly idle BLM's) and/or small changes to the injector constant to get the blms to slightly neg. values all over the operating range.

 

Agreed. Assuming the rest of the tune is dialed in (MAF calibration, etc), you may need to play with the injector constant until you get a good BLM (e.g. around 128). For WOT, you will need a wideband to get your PE tables dialed in.