Darinm

Hi all, question on an issue i'm pursuing right now with my fuel delivery.

1980 with new 383. I've been trying to get my fuel pressure up to 6psi which is what the carb builder recommended.

I'm using a mechanical fuel pump and a holley regulator with bypass. I'm using the factory hard fuel lines for the inlet to the regulator and the return line for the bypass on the regulator. From the regulator, i'm using all -6 AN fuel lines and fittings which next go to an inline fuel filter, then to the fuel log and to the dual fuel inlets on the carb.

I've replaced the fuel pump which is rated for 6.5 to 8 PSI. I've put in place a new regulator and with the engine running the max fuel pressure i can get is 5psi.

First, i'm starting to suspect my fuel tank may be dirty since across 2 carbs i've had my float stick due to trash in the bowl. Each time, i've pulled the fuel filter and didnt find anything so that parts still a mystery.

Second, could it be the diameter of my fuel lines ? Could it be the hard line and -6 AN lines are not able to deliver enough fuel to get 6psi of pressure ?

If i end up pulling the tank and replacing it, i may just switch to an electric pump and run new fuel lines.

Any ideas where to look next ?

Big2Bird

No where. 5 lbs is fine. Does it run Okay without starving for fuel?

REELAV8R

5 psi should be plenty. If it should starve for fuel I would check the size of the line from the pump to the regulator. Is it 3/8" or better?

Big2Bird

Has the in tank filter sock ever been changed?

Darinm

So far as i can tell yes. Carb has clear fuel bowls and it seems to be consistently full.

Darinm

Not as long as I've owned it. I wish there was a way to get a camera inside the filler neck to have a look around. Not sure if mine has a bladder or just a plastic liner in the tank to view the condition.

Darinm

Correct. From the hard line it's 3/8" ID ending in a -6AN fitting.

Big2Bird

Yes. You can look with a borescope type camera.
I actually changed the sender and sock via the fuel door. Rubber lines too. Just have to be patient.
The sock was collapsed.

george2066

cheat sheet for AN
6AN is 6/16 or 3/8
5AN is 5/16
4AN is 4/16 or 1/4
just put 16 behind the AN number

3/8 from tank to fuel pump then to carb, 5/16 return

MN80Vette

I have an '80 also and worked inside the tank when I switched to EFI. Your tank is lined, no bladder.

I had my tank out of the car because I modified the lines in and out, but I am pretty sure you can replace the sock filter from the top without removing the tank from the car.

Darinm

Thanks for the info. Tank removal doesn't seem too difficult. So it might be worth the effort to remove it, replace the sock and inspect/replace the lines while i'm at it.

Street Rat

You can remove the sending unit while the tank is in the car. You can get to it from under the fuel filler cover.

MelWff

have you tried reversing part of your set up, the fuel filter comes before the regulator.