Help wanted for power loss under load...

[C10Silverado79]

I have a 350 with a Q-jet 4bbl. I rebuild the Q-jet a couple of weeks ago and the truck has been running very smoothly. I haven't noticed any issues at all till Friday when I went to pickup a new Pontoon boat. Aside from having the aerodynamics of a brick, the boat and trailer only weight about 2000 lbs. The truck ran fine when with the boat attached until I started hitting some lengthy hills. Even though the hills were not real steep, the best I could do with the trailer was 50-55 mph. The big concern was when I hit WOT or close to it. The motor would stutter and surge like it was starved for fuel. If I backed off the throttle a bit it would calm down a little but would start acting up again if the speed dropped too low and I tried to accelerate. It even did this to me once on a slight down grade. Just lost power all of a sudden then smoothed out and was ok. The motor never stalled but a couple of time it literally would act like it stalled, the would surge, the 'pause' then surge then 'pause'. Over the past couple of months I put new plugs, wires, rotor, cap, fuel pump, water pump, hoses, belts, brakes, rebuild carb, vacumn hoses.

I'm not really sure where to look for the problem. I have no issues when not towing a load except that the I don't think the motor is as strong as it should be. Any ideas will be appreciated.

Thanks
Steve

[cableguy0]

Do you have any rubber hoses in the fuel system? have you replaced the pickup sock in the tank? Have you checked the fuel filters? Is the filter in the carb facing the right direction? Where is your timing set at?

[C10Silverado79]

The fuel filter in the carb was replaced in the past 2 months. IIRC, it's in correctly. I would think it wouldn't run right at all if it was backwards. I replaced the 2 rubber fuel lines that connect to the fuel pump when I replace the pump. The timing was on when I checked it after the carb rebuild, 8 BTDC according to the info under the hood. I have not done anything to the fuel tank.

[cableguy0]

The issues that your describing hauling weight while pulling hills sounds like a fuel issue. Thats when your gonna burn the most fuel. I would double check everything. Pull the plugs out and see what color they are. The absolute best time to pull the plugs would be while out driving on the highway with the boat. Just pull over and yank a plug or two. It will be the sure fire indicator of whether its going lean or not.

[powerdriver 1958]

Running outta fuel, single tank or dual??

[C10Silverado79]

Originally Posted by powerdriver 1958

Running outta fuel, single tank or dual??

The truck has a secondary aftermarket tank but it's empty and I don't use it. I had plenty of fuel in the main tank at at the time.

[powerdriver 1958]

If the valve is still in line it maybe a point of restriction also seen them part switch or suck air from the empty tank.just bypass it and that will eliminate it from the equation

[C10Silverado79]

Originally Posted by powerdriver 1958

If the valve is still in line it maybe a point of restriction also seen them part switch or suck air from the empty tank.just bypass it and that will eliminate it from the equation

Makes sense and I'd just as soon take the extra tank out of the truck anyway. How do you bypass the tank selector switch?

[C10Silverado79]

anyone have any other ideas to throw into the mix?

[C10Silverado79]

bump

[ChevyC102007]

Only thing I can think of is the float lvl, but Im not sure if that would be a factor in the case of a QJet. But you said you just rebuilt the carb so if ya followed the directions closely the float should be set close to factory specs.

I have to agree that you have air entering the system somewhere, have ya checked the base gasket to see if it sealed correctly?

[grinch4om]

this is a fuel delivery issue...all of the mentioned things to look at are good, float to low, sock in tank, sucking air from auxilary tank, hoses collapsed. I have run into similar things in the past. If you are able to, and safely, when it noses over badly, shut it off and pull to the side of the road. Pull the air cleaner lid, grab the throttle and stroke the lever, the accelerator pump will most likely not squirt fuel, an indication of a delivery problem. There are tests for volume measurements and pressures. Another fix I have done in the past has been a low pressure electric pump at the tank. This was necessary on drag vehicles due to inertia etc...

[C10Silverado79]

I'm resurrecting this to get some more input. I recently replaced the rubber fuel lines at the tank and took the extra tank and switch out of the system. It has not resolved the issue although the truck is running better. Today I could recreate the problem with just the truck. Got out on the highway, kicked the trans down and opened all 4 barrels. Between 60-65 mph the motor would buck and start to die. I can run 70+ with no problem if I'm light footed and only use the 2 primary barrels.

The sock in the tank is always a possibility but I'm hoping against it.

[westie 666]

Don't discount the coil, that can break down under load and give the same result