70 C10 resto-mod (was Chevy culture shock)

TIL that they sell APT retro kits for older q-jets. Prolly would have done this had I known, but now it's on the "maybe next time" list
 
guero_gordo said:
Been working way too much, so even though I bolted the q-jet back on weeks ago I didn't get time in to troubleshoot what wasn't working. Bowl wasn't filling, needle valve is stuck closed.
Beast runs fine when the bowl is primed, but shortly leans out and dies. Cracked the filter housing and fuel got that far, so clearly the pump was working, vacuum tested from the filter housing and it proved the valve was closed. Triple T technology (tap-tap-tap) had no effect. Tried with a little air pressure instead, no joy.
I had bench tested this with vacuum (upside down)when I put the valve in the seat after rebushing the throttle rods, but something must have bound up in final assembly.
Gotta pop off the air horn again. This time for sure
Click to expand...
Fuel in the bowl, because my assumption was faulty(and that valve will seal to vacuum when the FLOAT holds it closed, who knew). Accelerator pump was wonky indeed, need to hone the well and get another gasket on there, so she needed to come apart anyway. Going to Chem dip this beast since it's off anyway and blow out the passages best I can. I'm a little stumped as to why fuel ain't getting from the bowl into the manifold, but I'm pretty dense on this topic and most of my assumptions have been bad so far.
 
skipped the Chem Dip, brushed out the passages I knew about and bolted her back on. Accel pump works now, which provides a very useful indication that there's fuel in the bowl
Could not get her to stay running off the bowl, not on idle circuit, primaries, nor with choke, but I'm about 75% sure the carb is functional so I'll dick with the mix on the morrow. Not flooding.
I did remember to recheck the float+valve with vacuum while she was still off the truck and dry.
 
Hopefully all the alcohol jelly and sludge has been cleared out.
I suggest getting this book.
Pierre
 

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Back in my day, it was a necessity to know Rochesters. And if you can't make a Holley run, then you don't really have a feel how cars work. Carter is like a Rochester Lite. Then there's Mikuni and Weber if you ever owned a car from somewhere other than Detroit. I spent so much time on carburetors, but none of the books or parts kits I've amassed are useful now. I pulled the last carburetor out of a vehicle I own this year... because electronic fuel injection is king! Carbs mix the fuel perfectly sometimes, based on the metering circuits idle, main, enrichment, and acceleration, but EFI does it perfect all the time. And don't get me started on distributors. Ahem. That's all I'm gonna say about that.
 
pdentrem said:
Hopefully all the alcohol jelly and sludge has been cleared out.
I suggest getting this book.
Pierre
Click to expand...
Fortunately the carb was running fine before I rebuilt it, so all fault is mine, but she's clean.
I own that book, and keep referring back to it. Lots of information, but sometimes at odds with the way I absorb information. A wealth of "recipes" for tuners and engine builders.
Mostly, I keep coming back to bad assumptions based on inexperience
 
pontiac428 said:
Back in my day, it was a necessity to know Rochesters. And if you can't make a Holley run, then you don't really have a feel how cars work. Carter is like a Rochester Lite. Then there's Mikuni and Weber if you ever owned a car from somewhere other than Detroit. I spent so much time on carburetors, but none of the books or parts kits I've amassed are useful now. I pulled the last carburetor out of a vehicle I own this year... because electronic fuel injection is king! Carbs mix the fuel perfectly sometimes, based on the metering circuits idle, main, enrichment, and acceleration, but EFI does it perfect all the time. And don't get me started on distributors. Ahem. That's all I'm gonna say about that.
Click to expand...
I grew up on EFI, and it's essentially binary in most components, so things are either working or not working. Carbs are analog so two or more pieces kindasorta working seem much harder to diagnose.
 
"The idle tubes are the first restriction in the idle system and hang into the main body well below the fuel level. They should always be removed from the main body for any level of rebuilding since dirt and debris is typically found in and under them."
---Ruggles, Cliff. How to Rebuild & Modify Rochester Quadrajet Carburetors (S-a Design) (p. 26). CarTech Inc.. Kindle Edition.

I'm sure skipping that step won't bite me in the ass at all
 
Finally had a block of time to sit down with the machine, so I tried all the way from 1.5 turns out to 6.5. Primed-> cranked-> lit-> died every time.
Went back to 2.5 turns on the screws, advanced the distributor about an inch and sunumabinch if she didn't stay lit. Idling too fast and throttle response was goofy, but she didn't die. I just let her run, then backed down the dizzy to 4* and let her run some more.
I'll get back out there and dial in the idle mix with the vac gauge tomorrow.
Of course, I also noticed a leak at the intake manifold and the alternator is buzzing like it's a beer can full of murder hornets, BUT hey, she runs.
 
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