Tuning Advice Needed

[Barkett]

Greeting everyone! This is my first post, but I have been reading this website for the last two years.

Quick backstory... About two years ago I started to fix up my grandpa's 1977 Chevy C-10 Cheyenne with 77k miles. He had it parked in the basement for the last 30 years, always meaning to fix it up but never quite getting around to it. With the help of this wonderful site I was able to: replace the bed with an clean 86 and relocate the gas tank, replace both fenders, replace the entire brake system, fix a small transmission leak by replacing the filter and gasket, install new tires and rims, replace the high-pressure power steering line, replace valve cover gaskets, install a new radiator and thermostat, install new fan and clutch (which was missing), tear apart clean and rebuild the 4-barrel quadrajet, and tune the engine well enough to drive it around for the last year (~1000 miles). I just got the truck painted (on the cheap ~ $900), and will be getting a Rhino liner this Friday. So thank you all very much for your detailed posts, I truly appreciate it!

The only issue I have with the truck it during the first start of the day. The engine always turns over and starts, but will stumble and die within 3-5 seconds. I crank again, the same thing. Usually, by the third crank, it will idle well enough to put into drive and head down the road. After a block, it idles and runs perfectly. After the first start of the day, it starts immediately and idles perfectly each time after, even if it has been sitting for 8 hours at work. I have adjusted the choke thermostat per the manual and checked the timing and both are in line with the service manual. What could be the issue here?

I could post pictures or videos this evening if anyone thinks that would be helpful. Thanks!

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[Ricko1966]

Locate the float bowl vent in the air horn, take an old dish soap bottle and fill it with gasoline.Use the dish soap bottle full of gasoline to fill the float bowl through the vent before your next first start of the day.I suspect your float bowl is leaking fuel overnight and your having to refill the float bowl before it runs right.

 

[Matt69olds]

If it starts and dies repeatedly, your probably going to need to play with the choke pull off. It’s purpose is to open the choke just the right amount when the engine first starts.

First,with the engine cold, make sure the choke fully closes and the fast idle screw is on the highest step. Use a rubber band to hold the choke linkage closed, and then apply vacuum to the choke pull off. Note how far the choke pull off opens the choke against the tension of the rubber band. There is a textbook specification on how far the choke blade is suppose to open. You adjust it by either bending linkage, or turning the adjustment screw. If you still have the carb kit overhaul instructions it will probably have the specifications.

Next, remove the rubber band, reconnect the vacuum hose, and start the engine. Hopefully it starts and runs normally. If not, you may need to play around with the choke pull off adjustment. If the choke opens to far, you get the start/stall symptoms. If it doesn’t open enough, the engine will load up, foul plugs, black smoke from the exhaust, etc.


here is a video describing the process.

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[Matt69olds]

If your problem is it immediately starts, dies, and then won’t start again without excessive cranking, then the issue is fuel evaporating from the float bowl. Unfortunately, with the fuel blends we have to deal with today, that’s a problem not easily solved. Those of us driving with carburetors are a tiny fraction of the vehicles on the road today. Cars today have electric fuel pumps and closed fuel systems, fuel evaporating isn’t an issue for the vast majority of people buying gas.

If fuel evaporating is your issue, there are probably 3 solutions. First, live with it. Second, put an electric fuel pump on. That way you can refill the float bowl without cranking excessively. Lastly......as much as I hate to say it, the huge float bowls of the Holley carb are an advantage. It would take ALONG time for that much fuel to evaporate.

Personally, I’d either live with it, or install a electric fuel pump.

 

[Barkett]

Thank you both for your advice. I will try topping off the bowl before cranking tomorrow morning to see if that does the trick. I have been reading today about leaking plugs in quadrajets, it seems Cliff High Performance sells a plug kit. Does anyone have experience with that?

If topping off the bowl doesn't work I will take another look at the choke pull-off. Thank you for the video.

 

[C10MixMaster]

Thank you both for your advice. I will try topping off the bowl before cranking tomorrow morning to see if that does the trick. I have been reading today about leaking plugs in quadrajets, it seems Cliff High Performance sells a plug kit. Does anyone have experience with that?

If topping off the bowl doesn't work I will take another look at the choke pull-off. Thank you for the video.

the leaky fuel plugs are an issue mostly on the early Qjets, gm changed how they installed them and for the most part they dont leak. If you think that's your problem you can pull the carb make sure there's fuel in the float bowl and observe if its leaking. Evaporation is probably your problem, I have the same problem in the summer heat it cranks long the first time then its fine. I just live with it.

 

[Bextreme04]

Mine did this every once in a while. It seemed to go away when I readjusted my idle screws and raised the idle speed. I was running pig rich and the idle was low, when the choke came on it was even richer and would start fine and then the idle would drop until it died.

 

[Snoots]

Cliff Ruggle's kit is gold. Get it and install it.

 

[Ricko1966]

Cliff Ruggle's kit is gold. Get it and install it.

I've always just smeared on jb weld over them.Why is this kit so good?

 

[Dave M]

Side thought. I think people get used to driving newer cars with all the latest technology. They fire up with the push of a button, idle and run without a hiccup. My kids don't understand why l have a procedure, where l always like to go out and warm up my cars, and why it fast idles. Those who don't drive older carburetor have been spoiled.

 

[Swearbody]

When i encountered this it was because the fuel was leaking out of the carb through the bowl. There is a jb weld procedure to fill the bottom of the bowl that worked well for me until i swapped carbs. Just google jb weld quadrajet fix or something like that

 

[Swearbody]

Ill take a pic of my old quad that has this mod if you end up there
If you remove the carb cold and see fuel pooled you most likely have this problem

You can see where the jb weld is on the carb. You have to tear it down to do so its best to do when rebuilding the carb.

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[Swearbody]

well i guess you could pull it off without tearing it down now that im holding it

 

[Matt69olds]

The problem with JB Weld is eventually it cracks and flakes off. The constant heating/cooling cycles loosens the grip and causes it leak again.

The later carbs generally don’t have the leaky well plugs like the early Q-Jets did.

Unfortunately, we have all gotten spoiled with modern vehicles. Old iron has its own personality and quirks. Part of the fun is learning each old cars likes/dislikes. Some old trucks need one pump of the gas pedal, others need 3.

Once again, it’s just part of owning old iron. These trucks were expected to start every time, in any weather, and for the most part they did. You could have the more perfectly tuned, we’ll maintained truck, and still have minor drivability concerns that 99% of today’s drivers would throw a fit about. The problem isn’t the truck or maintenance, today’s fuel is completely different than what was available when these trucks were new. Cars today have closed fuel systems, EFI with electric fuel pumps. The gas that comes from the pumps are formulated for the majority of consumers. We carbureted dinosaurs knuckle dragging gear heads are a tiny minority.

 

[Barkett]

Update: I topped off the bowl this morning before cranking and still had the same issue. I then adjusted the pull-off and idle speed screws, after watching the 5 part video that was recommended, and the truck started on the next crank and idled perfectly. Success! We will see how it starts tomorrow on the first crank.

This is my first carburated vehicle, so I certainly have a lot to learn. I have found that I need to pump the gas pedal more than once in the winter for reliable starting.

That reminds me of a followup question. I have flooded the engine on more than one occasion trying to start in the bitter cold months. I was told by a friend that pushing the gas pedal to the floor will force the choke plate open to help clear the engine. However, when I do that the choke plate doesn't move. At that point, I typically remove the air filter and use a screwdriver to hold open the choke plate which always works.

Was my neighbor correct, should that work of my truck? If so, do I need to adjust something?

Thanks again for everyone's help