what is an LS1's average fuel pressure??
 

exacly how it says.. id post it in fueling but noboby ever answers stuff in there.. what PSI does a LS1 system run at usually???

when we tested mine it was a pretty steady 57 psi

k so i will definately need to upgrade my injectors on my 408 then hehe

Mine measured a steady 60psi.

what kind of pressure tester do you use??

Stock mine was 62 @ idle and would drop to 54 @ WOT
I installed a racetronix and it went up to 64 @ idle and drop to around 61 @ WOT

No matter what, you need to upgrade the injectors. I'm running 42#'s (which most people run) to give me a bit of room to play. Also should upgrade the fuel pump with a walbro 255lph or something of the likes, nothing crazy.

I mounted a gauge to the rail. Take out the shrader valve on driver's side rail. get a 4an to 4an coupling then 4an male to 1/8npt male and 1/8 npt to 1/8npt coupling then fuel pressure gauge 0-100psi with 1/8npt looks nice on rail too.

it's supposed to be a steady 58 psi at all times for what it's worth.

if it's dropping under load then there is a problem somewhere in the fuel system. If it reads a little high or low it's probably just the gauge you are using or a problem with the regulator built into the fuel pump unit (99+). On mine it actually reads about 60psi at all times but I think the gauge just read a little high.

so if i get 42 lb injectors is it going to force me to get a tune before i start it??? will an injector change mess things up really bad??? or will it work the exact same but just be able to flow more??

The GM spec calls for a constant 55-60 psi. This includes the Ignition in the ON position, idle, part throttle and WOT.

It'll definitely need to be tuned, but it will still be able to run and such, just like doing a head/cam swap. It'll run, but not as well as it would tuned.

bringing up a way old thread!! anyways, is it not supposed to drop under load and read the same when ignition is on without running? mine with ignition on when i first hooked it on the rail and turned ignition on it read like around 30. running was around 55-58 and under load it dropped to 50-52 or maybe less. do i need to check my pump out? got a issue im tryin to track down and thought it may be fuel related

Bigger injectors won't increase fuel pressure only a new/better/booster pump will help with that...sometimes an old ass fuel filter that's clogged will reduce pressure as well...I def would upgrade the injectors for a 408 though no doubt...