took my car out for a drive today at idle the fuel pressure was 42.5 on( factory regulator) and when i gassed it (wot) i saw no knock on the scanmaster. drove for about 30 miles.. when i restarted it to go home fuel pressure was only at 36 lbs at idle and when i punch it (wot) it startes pulling timing right away i also have the btm turned up to 3 so it's already pulling maximum timing. where did my fuel pressure go? is it starting to knock more because it was at maximum temp? any help would be appreciated thanks

 

I've noticed when I used the factory regulator, ambient air temperature had an effect on the pressure. The colder the weather the higher the pressure. I just assumed that when it's colder, the barometric pressure was greater and that was actually effecting the pressure.

As far as the knock goes, have you watched it before? I've seen problems with solid motor mounts and knock sensors. Could be a shield or header pipe touching something. Maybe the LT4 KM would be a good choice. Look at the signal when the engine is running. Try disconnecting the KS and see if the retard goes away. Also, test the signal from the sensor with KOEO by wrapping on the block with the handle of a screwdriver near the sensor.

 

well thought this was weird also. unhooked battery for night and pulled gas cap off. when i rehooked everything in the morning and restarted it fuel pressure was back at 42.5 again maybe the tank in seeing to much pressure? any way i have a lt4 km and have been monitoring knock before and always and have never seen any i'm still dumbfounded.

 

42 psi is way too high for idle pressure. the book says 41 to 47 psi with line off (wot). Idle(with line on) psi is to be 3 to 10 psi below wot psi(line off).