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Fuel pressure issues

padam

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I'm getting involved in drag racing again after about 20 years on the sidelines.

My car is a 73 Charger that was originally a 318 auto car I bought in 1981. In the 80's I modified it quite a bit:
413 with 906 heads, MP 484 lift cam.
Holley 750 vac sec, Torker intake, Holley blue pump.
MP orange box and distributer. Timing is about 38 total, no vacuum advance.
4-speed, 8-3/4 sure grip 4.30 ratio.

This combo worked pretty good before,
Used to run 12.50 at ,105 mph.
8:20 1/8. With slicks and open headers.

I took it out a couple times this year, running through the mufflers and on dot Hoosier tires.
It ran pretty crappy, sounded just as bad.

So I'm trying to fix a misfire condition at wide open throttle / high speed.
So far I have replaced plugs, wires, cap, and rotor.
Compression test was decent most 160psi, lowest 150 hi 170.

I finally installed a fuel pressure gauge I've had on the shelf for 20 years, and the pressure is good at 6 psi until I floor it then drops to under 3.
I disconnected the fuel line to change the Mallory filter, and the fuel just trickled out of the line.
I have fuel cell and some bits of the foam were in the filter.
It also looks like the foam was jamming up the outlet. See pic.
I pulled the foam out and it didn't look horrible, but obviously starting to degrade.
So I'd say 25 years is pushing the limits on fuel cell safety foam.

IMG_20200813_160239389.jpg
 
The foam can get everywhere. Take the pump, regulator and, carb apart. Clean them all. Then either replace the foam or leave it out.
Doug
 
The foam in a fuel cell is there for a reason. It keeps the tank too rich to blow up. Replace it and your good to go.
 
I'll probably replace it, although I see they sell new cells with or without foam.
I hate to remove a safety feature, especially related to fire.
 
The foam is for slosh and to disperse return fuel flow preventing aeration. Baffling could do the same job but foam is cheaper. If it related to volume/fire a stock tank would have foam.
Doug
 
The foam is for slosh and to disperse return fuel flow preventing aeration. Baffling could do the same job but foam is cheaper. If it related to volume/fire a stock tank would have foam.
Doug

Incorrect. If you take the foam out of a fuel cell it becomes a gas tank. The slosh part is a benefit but not the reason its in there
 
Definition & Description
Fuel Cell Foam is a special, sponge-like material that is installed inside a racing fuel cell.

Fuel_Cell_Foam.jpg


The foam is mostly air, so it doesn’t reduce the capacity of the cell. However, it provides a few key benefits:

  • It reduces sloshing.
    • This reduces fuel aeration and improves fuel delivery.
    • It also helps with weight distribution and vehicle handling.
  • It occupies the free space inside the cell.
    • This prevents fuel vapor and air from concentrating.
    • In the event of a fire, this reduces the risk of an explosion.
  • In cells with a bladder, the foam holds its shape.
There is always fuel vapor in a tank. So in theory the foam takes up space that could be holding vapor. But there's way more room for vapor in a normal 30 gallon tank than there will ever be in a 5 gallon cell. Does that stop you from driving your pick up?
Doug
 
Last edited:
Doesn't matter much to me now, pretty sure I trashed the motor yesterday.
 
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