Fuel Pressure Woes

Guys I need the power of the HAMB on this one!! I have a 351w with a 6-71 blower 2 Holley 600 vac. sec. Holley Blue Fuel pump, Holley regulator and 1/2 aluminum line from the cell to the carbs. I have the fuel pressure set 6psi and after the car runs for a few minutes the fuel pressure drops 2-3psi. All the lines are protected from the exhaust heat and the pump seems to be pumping just fine. Any ideas??????

 

Non vented fuel cap? Try running it with the cap off and see it that helps.

 

Fuel cell is vented. Tried running it with the cap off, but it does not seem to make a difference.

 

My gut is saying its the pump. Holley Blue pumps are junk. I went through 3 in the span of 18 months before I found one that was consistent. I'd test the pump.

 

Is there a voltage drop?

 

No voltage drop that I can find. I am running a liquid filled pressure gauge, starting to think that could be the issue.

 

Funny to come across your post as I've recently ran into the same problem. I run a SBC with two port Hilborn injectors on a 6:71 blower. My car is streetable and normally runs well. One day for no reason, it started to pop so I pulled over and noticed the fuel pressure gauge on the regulator was about 2 pounds so I turned the reg. in but nothing happened so I thought bad regulator. I changed the regulator and gauge but same thing - no reading. I then changed the fuel filter but same thing. I run a Holley "red" pump and it seems to be putting out.
It'd be interesting to see what's going on as I'm still on a witch hunt - sorry, didn't mean to hijack your post.

 

a Holley Black pump would be a good upgrade.

you didn't mention fuel filter. is your filter between the tank and the pump (wrong) or between the pump and the carb (correct)? electric pumps are designed to push fuel, not pull it. you can use a screen style filter before the pump, or use a filter sock on the pickup in the tank, but anything less than 80 microns can be a restriction.

 

check that liquid filled guage. We went through the same shit with D.W."s blown coupe and it was the liquid filled guages. I think we tried three before we threw them away and said to hell with um

 

forgot to say, we also had to lock the advance in the distributor and set initial timing at 34 degrees to get it to run consistent. The initial problem,acted like it was extremely rich one time and lean the next. It was the timing in the distributor centrifugal advance that would bounce around.

 

I have heard the liquid filled gauges have issues (when exposed to underhood heat I think). Try a regular "dry" one.

 

I have a 40 micron filter between the fuel cell and the tank. It would have been nice of Holley to tell me not to use that style of filter when I ordered the pump.

 

the instruction manual will tell you to use a coarse filter between the pump and tank, but not tell you what micron level is considered coarse. keep it above 80 and you should be fine. you can run a finer filter after the pump.
you also want to make sure the inlet and outlet of the pump are below the lowest point of your tank.
i'd also ditch the liquid filled gauge.
http://www.holley.com/data/Products/Technical/199R7914-3.pdf

 

Set the regulator at desired pressure while the motor is running

 

Well the liquid filled gauge was definetly the problem. I am no redoing the fuel filter situation. I am putting a 85 micron filter between the fuel cell and the pump and a 40 micron filter after the pump. Is there any reason I can't just screw the filter right into the fuel pump?