how much fuel pressure?

[a_turbo_stang]

Hey all I just got a adjustable fuel pressre regulator. Now I need to know how much pressure should I have it set at?
Here are my mods:
GT40 heads Cobra intake 24# inj, 255 fuel pump
1.7 RR
Those are the main things so where Should I set it? 38 psi? Thanks for the help.

 

[jaidedeye]

my engine is no where near stock but i run 38 psi with vaccum at WOT

 

[stangbear427]

Stock is 38psi @0"vac, and you should be fine with it. I'm running 40psi with intake and cam, stock heads, and it's fine. I may be a little richer than I have to be, but it's where I want it for my powerband. Stock setting is actually a bit richer than it has to be, so usually you can pick up a little HP on a bone stocker with an AFPR by leaning it out a bit. I'd start with stock with your set up, and work your way up from there to what it runs best with... you will probably find that you won't need more than 40psi at the most, and 38psi will probably be best.

 

[jrichker]

Use the SOP meter...

Get one of your buddies to ride along with you. Find a level stretch of road where you can do some testing. Don't choose a speed range that will make you shift gears, the shift quality & speed will affect your results. Use 2nd or 3rd gear and do a run from 2000 RPM to 5800 RPM. Call out the RPM as it increases and have you buddy record it and the elapsed time. If you have one of those cheap digital watches like I do, a stop watch is built in. Start the fuel pressure at 36 PSI, vacuum off and make a run. Turn it up to 37 and make another. Be sure to reconnect the vacuum every time you set the pressure. Keep turning up the pressure and making runs until you notice a drop off in time. If your bud was careful to record the results, you'll have a nice chart to use to find the optimum pressure.

 

[a_turbo_stang]

Use the SOP meter...

Get one of your buddies to ride along with you. Find a level stretch of road where you can do some testing. Don't choose a speed range that will make you shift gears, the shift quality & speed will affect your results. Use 2nd or 3rd gear and do a run from 2000 RPM to 5800 RPM. Call out the RPM as it increases and have you buddy record it and the elapsed time. If you have one of those cheap digital watches like I do, a stop watch is built in. Start the fuel pressure at 36 PSI, vacuum off and make a run. Turn it up to 37 and make another. Be sure to reconnect the vacuum every time you set the pressure. Keep turning up the pressure and making runs until you notice a drop off in time. If your bud was careful to record the results, you'll have a nice chart to use to find the optimum pressure.

Ok thanks I will give this a try this evening and see what will work the best. Thanks!

 

[a_turbo_stang]

Ok I have the fuel pressure at 39, it seems to like it there the best.
Now when I plug the vacuum line back on it drops to about 32 is this normal? Also when I just turn the key on it only gives about 30psi. Is this correct or is something wrong?