Lester

Did any one in this forum ever base line their 502 MPI motor with the later cool fuel system for fuel pressure at the rail ? Read a lot of post but didn't see the witnessed test pressure from a stock regulator..........Thanx

alter ego

I HAVE A 502 MPI TOO..I AM NOT SURE WHAT THE EXACTS ARE. MOST GM PORT FI SYSTEMS ARE BETWEEN 30 AND 40 PSI ON THE RAIL. I HAD A MOTOR RUNNING 36 PSI STOCK AT IDLE.

liquid asset

mine was 36, I think I have a adjustable regulator if interested

Ric232

The latest 502MPI's were actually 43 psi. I don't know when that started.

blownboat

The mercruiser service manual lists 2 differant fuel pressures. It depends on wich computer you have. MEF1 MEF2=34-38 psi MEF3=41-45 psi

ursus

36 psi if you have the earlier Vapour Seperation Tank system, 43 on the later cool fuel models

FBRONCO

What is it on a 454 mag with a VST?

Ric232

Same as the 502. 36psi.

Lester

Are all these pressures at Idle? Both of my motors idle in the 40-42 range but under a load at 3500 both drop to 36 psi. Mine is a 99 cool fuel set up. One pump is new the other is 3 years old. I'm trying to determine if it's worth putting the adjustable reg on, if I already have a pressure drop when the injectors are under a load then adjustable regs will only boost press at idle which is where it's not needed? Built both motors and had ECUs remapped over winter......test and tune time