I'm about to surrender !

[1tonson]

I have a 83' c-10 350 auto. this truck runs top notch, except when its in a pull, or after the 4 barrel kicks in, it runs hard until it feels like its running out of gas, let up, and stay at part throttle runs great. above 60 mph it starts cutting out. change the distributor, spark plugs, wires, 3 differnt carbs, the fuel pump shows 17 in. vac, has a new gas tank, but old sending unit. all this and it doesn't change a thing what gives ? Any help would appreciated.

[VileZambonie]

Check for kinked fuel lines

[1tonson]

yea, i blew back through the line at the pump. but the tank was full. coudn't really tell if alot of air come through. what a plug exhaust, converter, symptoms be ?

[TexasRed]

Did you replace the fuel filter in the carb?

[VileZambonie]

Just trace the fuel lines back. Make sure no rubber hoses are kinked or that they can kink.

If you think you have plugged exhaust hook up your vacuum gauge and tape it to the windshield. When it acts up observe the vacuum reading. If it's at zero your exhaust is plugged.

[1tonson]

humm. i guess its not "plugged exhaust" its  quick to return to 15 and steady, after wide open throttle . This truck has 3 line sending unit. but only 2 are hooked up. I'll keep trying-thanks

[gmtech2]

i had an 84 that did almost exactly what your talking about when i was in highschool. didnt know much then so kept trying diffrent things and couldnt figure it out. eventually i found that the dual tank switching valve was stuck part way between tanks. this causing a restricted fuel line and couldnt find it by checking with air or with a pressure gauge. it will restrict fuel to much and cause it to misfire or cut out at higher loads and upper rpm where you need more fuel. to prove this i just bypassed the switching valve and went straight off of the left tank feed and it cured it. replaced the valve and it never acted up again. might try that

[Cowboy_Customs]

I know you said distributor was replaced, but what about the timing advance? I had a 78 350, good vacuum lines, good vaccum, holly single feed 600CFM 4 BBL. Ran good, but no power on top end, or when the 4 bbl was wideopen. Found out the vacuum advance was bad.

[1tonson]

Yep, "kinked line' actually "twisted" i had looked just in passing(lazy) but really got up close and noticed shiny mark under the bottom of the cab (driver side) looked like maybe a stick. the line had twisted almost shut.  "thanks for the advice" I always appreciate helpful criticism.