Blackroc86

I have a Holley blue pump that puts out 14psi. I have one race left this season and wondered if I put a half inch line from the fuel pump up to the regulator would I get any more volumn to the carb.

five7kid

iTrader: (14)

Do you need more volume?

Blackroc86

My fuel pressure guage is dropping from 8psi to under 5psi during a run. Sometimes as low a 4 psi.

AM Racer

It would have the potential to deliver more if the fuel system is up to par.
Has it always had this problem or is this something that just started?
It could be the old line or the pump losing efficiency or an obstruction at the pickup.
Several variables to think about.
It may even be a voltage issue supplying the pump not allowing it ro run to it's full potential.

Blackroc86

The problem may have been there before when I was using the TPI pump. I recently removed that pump and put a fresh tube in its place. Then put on the Holley Blue and added a fuel pressure guage outside the windshield so I can see what is happening. We have checked the voltage at the pump and it is within spec.

IHI

iTrader: (1)

I'm running -10 aka 5/8" line from my tank to the carb. When I had to install the Holley red as a back up, I had 8 psi at an idle, and 3psi at WOT right out of the gate and it ran terribly. Got a pressure relief spring from a Holley black pump and installed it in the red pump, cured the pressure problem. Idled at 8 psi, went down the track at 7 psi, then it quite the sputtering/surging at the top of the gears. The bigger line will generally allow more volume, but with the smaller fuel pumps not the pressure, and you have to have the pressure to get volume in these big lines

Blackroc86

IHI do you remember how long the spring was in the Holley Black? I got one supposedly from a black pump from the local speed shop and it was half as long as the one that was in the Blue. About 1.25 inches compared to 2.25 inches in the Blue.

IHI

iTrader: (1)

If memory serves correctly, the springs were the same length between the red and black pumps. Spring pressure was much tighter with the black spring though. If there was a difference it was not anywhere near an inch because we all would have seen that, but all we all noticed was the tighter feel of the black spring.

Blackroc86

I assumed it should have been a stiffer spring but this is what the guy at the speed shop gave me. Oh well the quest continues.

IHI

iTrader: (1)

If it's that short I dont see anyways for it even seal to build pressure, the passage way in the pump is longer than that. I dont know how excited you are about trying it out, but it does'nt take much to change it. Helps if you have pliable lines so you can clamp the hose on the inlet side of your pump so gas loss is minimal, then it only takes like 1 minute to swap them out if that.

Blackroc86

I did try the shorter spring the shop gave me and the fuel pressure drop was worse as I suspected. I will see if I can find a Holley Black pump for next weekend and try that.

IHI

iTrader: (1)

If it dropped that bad then obviously the spring was not right. Weather you can get the whole pump to bolt on and try, or just borrow the spring from it for a few passes my money is that it'll make the car a whole lot better. I think alot of the ney-sayers about overkilling the fuel system have never had a guage on their car going down track to see the amount of drop depending how it's set up. Sometimes they claim a gain of .1-.2, with mine using the red pump and then installing the black spring I picked up .2 personally, so that shows something. Good luck and let us know the results.