Truck carbs, FPRs, high fuel pressure HELP!!

[Blue250X]

Ok, I just swapped a carbed 350 into my 1993 Chevy truck. It has an in tank electric fuel pump. I heard this makes too much pressure for the quadrajet carb, so we put a holley fuel pressure regulator on it. It runs, but not good or smooth, I'm not blaming it on the fuel pressure but the carb leaks a bit, but the last 2 quadrajets did also. Could this be from too high of a fuel pressure, or using a carb out of a buddies junk yard? I just ordered a demon carb but I don't want to ruin it with too high of fuel pressure. Will it hurt the new carb? Also does anyone know how to adjust the FPR? I see the screw but do not know which way to turn to lower pressure. Thanks guys!

[trailrider1156]

in tank pumps can easily run 40 lbs pressure. carbs like 5-7 lbs. maybe email holley about how to adjust the regulator. i have a pressure guage inline on my V8 S-10. yes, running too high pressure will hurt the carb. get the pressure right before you put the demon on.

[Blue250X]

Alright, thanks, the pump is from a TBI engine which i read only run like 12-15. I will also contact holley (or try) before i start adjusting.

[trailrider1156]

i checked out the holley website and if you go into the products and find the FPR's they have the instructions for them and it will show how to adjust. BTW, the holley FPR should have been adjusted pretty close when you got it.

[Blue250X]

Originally posted by trailrider1156
i checked out the holley website and if you go into the products and find the FPR's they have the instructions for them and it will show how to adjust. BTW, the holley FPR should have been adjusted pretty close when you got it.

Alright, thanks for the info, and I got it from a buddy who got it with his car, so I have no idea what has been going on with it haha.

[Blue250X]

Alright, I got on the website and it says screw out for less pressure, sweet!!! Thanks alot trailrider!

[Striker49]

Yea, the TBI pumps run low pressure, around 11-13ish I believe but don't hold me to that.

From my understanding, Carbs run pretty low, EFI run high and TBI/TPI run in between.

[Blue250X]

Originally posted by Striker49
Yea, the TBI pumps run low pressure, around 11-13ish I believe but don't hold me to that.

From my understanding, Carbs run pretty low, EFI run high and TBI/TPI run in between.

TBI/TPI = EFI :confused: I think maybe you mean a multi-port fuel injection (MPFI) which do run higher, maybe around 30-50. The carbs I think run 5-7? But yes the TBI does run higher than carb, but lower than MPFI.