Q-jet runs out of fuel

[Mongoose 79]

I have a 79 corvette with a mild 350 and a 5 speed manual .Im running a Q-jet # 17058204 I did have a750 Holley and switched because the Q-jet just has better street manners not to mention better fuel mileage .My problem is at wot just about the top of third gear the carb runs out of gas .I have rebuilt the carb and installed a edelbrock # 1980 high flow needle and seat and raised the float level to 1/4 inch with very little improvement I have put my Holley back on and it runs fine so I'm pretty sure I have a carb problem. I really would like to make this carb work so any help is very much appreciated

[carmantx]

Get a float and good needle/seat from Cliff.
Do you have a fuel filter in the inlet?  Might remove that and have external filter.

[77cruiser]

Check the fuel pressure at WOT.

[Cliff Ruggles]

The symptoms are fuel delivery if you have the large fuel inlet seat installed.  Even a stock pump and fuel system should be able to keep up with a mild 350 engine provided the fuel inlet seat is at least .135"......Cliff

[Mongoose 79]

Thank everybody for there response
My fuel system consist of a edelbrock electric fuel pump just below the fuel tank and a stock pump on the motor with a fuel regulator and gauge I have a prefilter before the electric pump and another filter between the regulator and the carb I have removed the paper filter in the carb my fuel pressure is set on 7psi the edelbrock 1980 needle and seat is a .145 but it is not a window style seat I don't know if that makes a difference I have checked all my fuel lines back to the tank there is no sock on the fuel pickup I've not checked pressure at wot but like I had mentioned in the original post I can bolt my 750 Holley on and it does fine at wot I'm bound and determined to make this carb work it's so much smoother than the Holley

[73ss]

I'd would guess the holley would do the same thing if you stayed in it long enough. It's gonna take longer because you have 2 bowls to empty instead of 1. Your problem probably has to do with the missing sock. Pusher electric pumps can sometimes cause problems as well. By comparison I have a 68 L-79 vette, which was a healthy small block in the day. Other than a edelbrock q-jet it is 100% stock. Pump, lines, filter all of it. It pulls all day to 6500 and has never hinted at running out of fuel, Other than on a hot day after a heat soak. My tank is bottom feed and your's is top feed? Other than that It's the same setup. One thing I've learned after all these years is the factory knew what they were doing. Look at a LS-6 or a tri-power poncho. Nothing fancy just a single pump.

[77cruiser]

The float isn't being stopped from dropping far enough is it?

[Pat]

Sounds like fuel delivery issues.  Simplifying your fuel system back to stock form should really help.  A good quality mechanical pump that delivers proper fuel volume at NO MORE than 5 psi will save the day.  Avoid any type of fuel line installed filters (they invite air pockets) and go back to the free flowing (no back flow valve) paper filter in the carb.

Go ahead and readjust the float level back to normal.  Raising the float level will only give you a richer mixture and will affect fuel economy.

[Pat]

On another note, it is possible to confuse fuel starvation with an overenriched mixture:  They will both shut off your engine during heavy throttle.  A thick black cloud of smoke just before the engine shuts off is a sign of mixture enrichment.