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Old 07-28-2022, 09:05 AM   #18
72c20customcamper
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Join Date: Jul 2018
Location: Catskill Mountains,NY
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Re: 1968 GMC 250 Inline 6 4.1L Chugging

Quote:
Originally Posted by Jason Banks View Post
I've held off commenting, but my 1968 with 250 has basically the same problem.

I've always thought it was a fuel problem. I have HEI and have rebuilt carb a couple times. Truck also has a new fuel sending unit/pickup and the tank doesn't look like it has trash in it.

I loved hearing 72c20customcamper say that it was a fuel line collapsing because the symptoms he was describing is just like mine, slight incline, near WOT trying to go 69-70mph on the highway with 4:10 rear gears. It starts bucking and you have to let off the gas and slow down for it to get better. Doesn't always happen, you can run for miles at about 70 then it just chokes.

Interested to hear what you find out. I'm thinking I'll inspect the rubber lines, but I know I've replaced those in the past. Might try something stiffer, like some PTFE lined AN line. I've been neck deep in my other truck and kind of neglecting the other one...
My truck was giving the classic vapor lock symptoms . One day it did it and I killed the ignition and pulled over . I had a clear filter on it just to see if there was crude in the system . The filter was dry and then it slowly started to fill . The hose was real mushy from oil soak from the outside . Oil and gas line dont mix not made for it I cringe when I see it used on transmission coolers knowing it will fail. Changed it out and never had the problem again .
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72 c20 custom camper Husky edition,
66 SS396 Chevelle 1964 Hawk, 63 Avanti,62 lark
1969 AMX ,
1968 c20 stepside ,85 K20
1977 Suburban sold
68 anniversary.
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