I've got a an 8ba with a Holly 4 barrel. All at once it started running rough. I think it's getting too much gas, if I unhook the electric fuel pump it smooths out, until the gas is used up then if I plug the fuel pump in soon enuf it smooths out. Till it gets too much gas again what do I do?
What size carburetor do you have? and are you using a fuel pressure regulator? 500 cfm is what I used on my Flathead.
With the crappy gas today I would not be surprised if the filter was eaten away, thus increasing the fuel.
this is normally a sticking/leaking needle valve, or in rare cases, the float could be sinking, there is a very remote chance that the relief valve is not working in the fuel pump, causing very high pressure, .
checked the needle valve and replaced the float. put it back together and it still does the same thing. next step is the fuel pump, but I can't remember the correct pressure rating for my engine/carb. I think it should be lower than normal. anyone have any advice?
I'd thinkF&J and rer_239 are on the right track. Something is letting or causing fuel to leak past the needle valve. We are assuming it is running rough at an idle and not at 60mph down the road.
We should have had you look down the carb throat to see if there is gas leaking in there. If it stays dry with the electric pump on, then the needle is not leaking, and the pump pressure is not high enough to lift the needle. so I would look in there you'd be looking for gas dribbling, or some sort of gas leaking steady, not just damp looking. .
On a four barrel, you need to look in the back barrels too. That also has a float and needle to cause the same issue .
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