Technical & General Discussion Area > Tech Torque Pre 1973

Autolite 4300

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66dreama:
Hi all
After some advice please
I am having issues with my 4300 carby sitting on a 302
It is weeping around the top seal
It has been rebuilt and we have tried adjusting the float levels numerous times
 To and below factory specs
I have now checked the fuel pressure
Carby specs state a max pressure of 5.5 psi
My fuel pressure gauge is saying the pump ( correct new replacement ) is putting out 7 psi
Could this be enough to cause the issues I am getting
 Seeing
Each time we remove the top of the carb the fuel bowl is full
Have checked and rechecked needles seats idle-circuit etc
Everything works well except for the high fuel level which we cannot resolve
PS the amount of fuel coming out is minimal just enough to make the immediate area look damp ( no pooling or runs )
Any help appreciated
Thanks
Paul

Chris66pny:
Hi Paul,

I had a similar issue on a Holley 4150, i rebuilt the carb and it fixed the problem but in my research it was fairly common for higher fuel pressures to push fuel past the float needle. 7PSI isn't all that high but it could be for that carb, might be worth throwing in a fuel  pressure reg or even a cheap 30 micron filter between the pump and carb (filter dropped my pressure by 1-1.5PSI).

Hope this helps.

Cheers
Chris

66dreama:
Thanks Chris
Hopefully I can pull the pressure back slightly
I’m curious to know if such minor overs can cause the need for to unseat
Cheers

barnett468:
either the float level is too high or the fuel pressure is too high or the needle and seat is leaking or you have a sunken float.

the stock needle and seat "should" be able to handle 7 psi, but who knows with some of the crummy aftermarket parts they make today.

You can actually remove the top of the carb and run the engine to see exactly what is going on, but be aware that some fuel will squirt out of the needle and seat area, so wear safety glasses and be careful.

You can also remove the top and remove the coil wire and turn the engine over a few times to build fuel pressure, then see if the needle and seat are still letting fuel by.

then push down on the float a tiny bit slowly, and it should squirt gas out the needle showing that there is pressure. be careful when gas shoots out.

i would try these tests with the fuel pressure at 7 psi first, but on a stock engine and carb, slightly less pressure is better

evan:
Years ago, I was told that new pumps have too much pressure. Mine was pumping 7 PSI so I installed a Holley Pressure Regulator & set it to 4 PSI. Never had a problem with my 4100 Carb.

Evan.

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