RADustin
Full Access Member
- Joined
- Mar 27, 2017
- Posts
- 111
- Reaction score
- 8
- Location
- New Orleans
- First Name
- Dustin
- Truck Year
- 1976
- Truck Model
- C20 Crewcab
- Engine Size
- 454
Hi,
I recently purchased a '76 c20 CCLB with a non original 454(3rd digit L) and a granny 4spd. I haven't pulled the numbers off the engine but I have bought all the ignition parts and a coolant temp sensor for a '76 c20 with a 454 and everything has worked thus far. Engine 'looks' original, but I know it isn't.
Pic-
I'm having some problems with a random stumble here and there, where the cure is to throttle the pedal a little on and off(mostly off) and the engine will come back smooth and I can continue. Heat and/or runtime definitely effect how often it will stumble. Also, under more load vs less load makes a difference(fuel consumption). All the ignition is new and I have moderate confidence it is good. I may change the HEI module again to experiment.
I'm going to rebuild the carb with the edelbrock 1921 rebuild kit and see how that works out. The truck is a dog on power, so I am hopeful this will wake it up a little. None the less, when I do call on the power it usually stumbles anyways. Entering the freeway has become a chore.
My concern is in fuel delivery. I have a bastardized system, so I know I may not be able to get definitive answers here but maybe I can bounce some ideas around as I investigate further.
My eventually goal is to shortbed the truck with a factory shortbed tank setup from a later model truck with a drivers side tank and fuel door. I plan to remove all the current mess and probably run some new hardlines up to the front of the truck.
In the meantime, before I shortbed the truck, I'd like to ensure the fuel system is as 'correct' as I can manage- at least cure the stumble
My questions are-
I'm interested in any conversation I can generate, I appreciate any help or ideas. I'm going to mess with the truck again in the next few days and play with some more ideas.
I'm going to try to inject propane in the carb when it stumbles, see if it cure it to ensure it is a lean stumble. I'll also rebuild the carb and see how that does. I'll report back my findings.
Thanks!
I recently purchased a '76 c20 CCLB with a non original 454(3rd digit L) and a granny 4spd. I haven't pulled the numbers off the engine but I have bought all the ignition parts and a coolant temp sensor for a '76 c20 with a 454 and everything has worked thus far. Engine 'looks' original, but I know it isn't.
Pic-
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I'm having some problems with a random stumble here and there, where the cure is to throttle the pedal a little on and off(mostly off) and the engine will come back smooth and I can continue. Heat and/or runtime definitely effect how often it will stumble. Also, under more load vs less load makes a difference(fuel consumption). All the ignition is new and I have moderate confidence it is good. I may change the HEI module again to experiment.
I'm going to rebuild the carb with the edelbrock 1921 rebuild kit and see how that works out. The truck is a dog on power, so I am hopeful this will wake it up a little. None the less, when I do call on the power it usually stumbles anyways. Entering the freeway has become a chore.
My concern is in fuel delivery. I have a bastardized system, so I know I may not be able to get definitive answers here but maybe I can bounce some ideas around as I investigate further.
- The carb is an Edelbrock Q-jet 1906. Brand new in-carb filter. No other filters present except maybe the socks in the tanks.
- The fuel pump has a return line, but it is capped off.
- The truck has both fuel tanks, but only a single fuel line goes to either tank. Then on the outboard side of the tanks I can see the fill hose and maybe a vent line? No return line, no wire for the sender on either tank. Fuel gauge does not work. I believe it is stuck past full(sender goes 0 or 90 at full?)
- A mechanical 3 way valve is mounted on the drivers floor board that switches the 2 gas tanks to the single pump feed. It seems to work as I have switched back and forth across the tanks several times with success.
- The fuel lines are kind of a mess of some original looking metal lines and some 'custom' rubber lines/clamps.
- The line from the pump to carb is metal from the pump up to behind the alt of the passenger head. Then it goes to rubber to the carb(I replaced this). I made the rubber line kind of too long so it bends out over the valve cover and goes straight into the carb, instead of laying on the intake mani. My idea was to reduce fuel temps, encase fuel vapor was the problem.
- everything on the HEI is new except the vac advance. I'm changing that this weekend. New plugs/wires. When I initially put the new HEI parts in it, a clutch out right off idle stumble cured, but returned. I may put another module in it to see if it cures this. Maybe the truck is eatting HEI modules?
My eventually goal is to shortbed the truck with a factory shortbed tank setup from a later model truck with a drivers side tank and fuel door. I plan to remove all the current mess and probably run some new hardlines up to the front of the truck.
In the meantime, before I shortbed the truck, I'd like to ensure the fuel system is as 'correct' as I can manage- at least cure the stumble
My questions are-
- Is the fuel pump return OK to be capped off?
- Is the return needed?
- could no return cause my stumble?
- could maybe no tank vent cause the stumble? Is the cap vented?
- engine has got harder to start now that the truck is in a much hotter environment. (bought truck in NJ, I'm in south LA) Everything kind of sounds like a sort of vapor lock?
- Does anyone have a diagram for a standard short bed truck setup? I'd like to get an idea of how I will run it in the future.
I'm interested in any conversation I can generate, I appreciate any help or ideas. I'm going to mess with the truck again in the next few days and play with some more ideas.
I'm going to try to inject propane in the carb when it stumbles, see if it cure it to ensure it is a lean stumble. I'll also rebuild the carb and see how that does. I'll report back my findings.
Thanks!
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