Lean mixture at high revs.

[Z-linkCobra]

FWB... you need to buy some new needle and seats...lol. We run 8.5 to 9 psi on the race car all day long with no flooding problems.


Fatboy... FWB is right...3/8 o.d. is too small. You need to step it up to 1/2. Pressure is not the biggest factor its volume that you need. With a 750dp your going to run out of fuel with the small line and the restriction of the mechanical pump. Ever taken the line off of a mechanical pump and cranked the motor over...huge pulses in the fuel flow..not a steadt supply. Perfectly ok for cruising and pulling the CObra to the show...but not for going fast.

[FWB]

8.5-9 psi....i would bet not with regular stock neoprene needles. the solid needles will take that much.

i don't think the filter before the pump is a good idea either. the pump should be below any possible fuel level in the tank.

[FatBoy]

If I by-pass the mechanical fuel pump, can I just disconnect both pipes and join the ends together or do I also need to remove the pump and fit a balnking plate over the hole?

The base of the pump is level with the bottom of the chassis rails, so it is as low as it can go and is below the fuel level in the tank.

Many thanks for your input and the benefit of your experience.

Paul

[RICK LAKE]

FatBoy Paul Try the simplest way first. Take the mechanial pump out of the loop. road test the car and do the same test for fuel pressure. Have the pressure at 6 psi. If the car doesn't change and the pressure is still dropping more than 3 psi we need to look at the supply system and pickup in the tank.
I know that most cobras came with a 3/8" and 5/16" supply line for a carb car and mechanical fuel pumnp on the motor. The carb was only about 750-780cfm. Today 1,100- 1,300 cfm carbs are out there. Unless you are running a pump in the fuel tank, I see a couple of problems,
Under hard accel the fuel is being pushed to the back wall of the tank. If you are around or under 1/2" a tank of fuel the pickup may be sucking air/fuel combo. This doesn't work to well for a motor and lean condition happens. If under normal driving this is not happening, fill the tank to 3/4 full and try again the hard accel. If no problem happens the issue is the pickup in the tank. I have had to change my tank and rework the baffles. I can't run lower than half a tank of gas without having the same problem as you in high "G" turns or accelleration. If there is no change the next thing is to look at the fuel filter for possible clogging and partial flow. The newer gas out with 10% ethenol is eating any rubber hoses you have on the car. Very small pieces of the rubber are clogging up, filters jets, needles and seats of the carbs. This has happened to a couple of guys here this year.
If the electrical pump is not getting the job done, I doubt the mechanical will fair and better. The next thing would be to run a larger line from the pump in the back to the tank and repeat the drive. If car gets better you have your answer. If not start looking at the carb. Ps I run 1/2 line to my all my cars and 3/8" return line with a good fuel pressure regulator at 6.0-6.3 psi. This system never drops more than 1 psi at WOT. The other idea I have is the fuel is cooking in the lines. I would rap the supply line with a deflector tape and foam insulator. Last Question Does this problem happen only when the car is hot? and not when cold or warming up?? Rick L.

[Z-linkCobra]

Originally Posted by FWB

8.5-9 psi....i would bet not with regular stock neoprene needles. the solid needles will take that much.

i don't think the filter before the pump is a good idea either. the pump should be below any possible fuel level in the tank.

Of course....who runs stock anything on these cars....lol.