Ok, I have some questions. Car is a 91' 350 tpi, I am trying to understand some things here. Ok, so one can datalog and see the logs and determine that car is running rich down low or lean up high . How does base timing and fuel pressure come into play here? and i am talking from the mechanical side of things? I mean ,for example, i can adjust the cars timing and fuel pressure manually of course, and that would make it run a lot different too. So, where should my TIMING AND FUEL PRESSURE BE PRIOR TO DATALOGGING? and prior to making changes?? Say i have my fuel pressure set lower to like 42.5 psi and timing feels better at 2 degrees btdc now, then would that throw the datalogging off? at 6 degrees btdc my car doesn't ping ,but it is sluggish and it feels like way too much timing. It runs better at 2 degrees. So, what i am asking is: Should i leave fuel pressure regulator and distributor timing alone and then datalog and then determine what changes need to be made in the prom?

 

Yes.

 

There are two things to consider.
In the Prom there is a setting for "Injector Constant".
This sets the calculations for fuel based on what is thought to be there.
Lowering the fuel pressure makes the injectors "smaller" than what is programmed.

There is a "Base Timing" constant to indicate where the distributor is physically located.

If you change timing, the indication will be off by that amount and the fuel calculations will need to be tweaked by the correction routines (BLM) to be at the correct response output on the O2 sensor.

Its best to get those two to match what is programmed so things are not skewed.
While it won't make things worse, the mental games of remembering will drive you nuts after a while.

Check the values that are programmed in the stock bin file.
Should be 19# injectors at 43 psi and 8* BTDC on timing IIRC.
Double check your exact bin to be sure.
Jp