Hesitates like running out of gas while under load

I have a 78 Chevy 1/2 ton 4X4 with a 350. The engine has about 78K miles on it. The transmission is brand new. The truck will start fine, idles good, and you can rev it up (while in park) with no
problem...runs nice and smooth. When I drive it, after a couple seconds of accelerating, it starts to hesitate, surge and, if I don't back off the gas, it will eventually stall. It feels as if it is running out of gas. I have replaced cap, rotor, wires, ignition module, coil, carburetor, fuel filter and fuel pump and there is no improvement whatsoever. I checked the timing and it looks good. What next?
TIA,
ngpost1
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if you have a quad4mv carburetor on it, they have an internal filter in the inlet to the carburetor. This will plug up and then a spring in front ot it pushes it back to allow some fuel to enter, then closes again. Results, a surging engine when power is called for. runs like you said. throw the filter and spring away and use an external filter. john

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BETTER YET!!! Replace the filter in the carb with a new one! If you are running an in-line filter AND the in garb filter, throw away the in-line filter. The in carb filter is MORE than adequate! If all the fuel filtering is new, check any soft-lines that are on the truck for deterioration and or kinks. Also check all the hard-lines for kinks. If all is good so far, drop the tank(s) and check for a strainer IN the tank on the inlet line on the sending unit.

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Looks like it was the strainer in the fuel tank. I disconnected the fuel line and blew compressed air through it (don't forget to take off the gas cap) and it seems to be running fine now.
THANKS!!!!

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You may have a cracked valve. Check your cylinder compression. If one's lower than the rest, you have a problem. If a valve is just slightly chipped on a edge, I've seen that exact symptom before, it would only miss under load, unfortunatly for me it was my truck that time. A compression check easily pinpointed the problem, and sure enough when the head was pulled, a chipped valve. Only after I replaced all of the parts you mentioned as well.
Ken
ngpost1 wrote:

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somewhat related question...the 355 (heated right up) in my summer toy will behave as if its starving for fuel when really hot, on high speed runs. When its cold, the car goes like a bat outta hell...I can do several foot-to-the-floor-till-it-runs-outta-power runs with no problems...do it when its hot outside and the engine is hot, forget it!! it'll make power till about halfway thru 2nd gear and then stumble and fall down till you let off....feather the throttle and it comes back!!
any thoughts? the car runs too strong to have any broken parts inside, and this problem is temperature related...and very intermittent.
?
b

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sounds like either fuel filter plugged, or pump is not up to par when it gets hot
if you have a scanner, watch the O2 sensor readings when it starts to stumble, they will go lean

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Try replacing the spark plug wires...worked for me... gk

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