Now carb woes.

F

FordCustom

Senior Member
Slowly but surely bringing this truck back from the dead. 8BA with a Holley 94(Ford version). Well, I got it to start and idle a little without using gas poured down the carb, but.... One start it idled well, but died. The next time it had an odd idle like a race car, real lopey. Then third and fourth starts the engine idle went up and died, then tried to run away on me. I did the only thing I could think of in that split second, and clapped my palm over the carb. WOW, that thing had some vacuum! So now I am thinking I didn't do so hot on the carb. It emptied a half quart of gasoline from my gravity feed fuel source.

Bad float level?
Needle on the float sticking open?

That's the two I think of right off hand. Any more thoughts? It was awesome to hear it crank and idle so smoothly the first time. Hopefully I can get this narrowed down, and be able to do a little tuning on it.
 
Did you rebuild the carb yourself? Some of the kits don't have the right parts , at least they aren't made right. I would be looking where JWL said as a bad float will usually just flood out and kill the engine because it dumps so much gas in it. When I first tried rebuildin mine it was doing what yours is and it was an incorrect power valve and would not seal. Fill the bowl with gas and let it sit then take off the bottom of the carb and see if gas is leaking out the power valve.
 
The rpm should not have much of a rise to it off idle unles the throttle plates are opened up. If fuel is leaking from a stuck float, improperly adjusted float, or a leaky powere valve then it should just get an extremely rich mixture. The mixture range for internal combustion engines is between 12:1 and around 18:1. Much above or below those ratios and it won't run. Check for any signs of internal fuel leakage or air leakage below the throttle plates and make certain your throttle body is rigged correctly for idle and rpm control.

A leaky vacuum diaphagm in the old Load-A-Matic distributor can give you problems too.
 
When you rebuilt it did you check the float for a crack or leak? Bring water to boil set the flat in it if you see bubbles you have a leak, what rotorwrench said also would be my guess.
 
rotorwrench said:
The rpm should not have much of a rise to it off idle unles the throttle plates are opened up. If fuel is leaking from a stuck float, improperly adjusted float, or a leaky powere valve then it should just get an extremely rich mixture. The mixture range for internal combustion engines is between 12:1 and around 18:1. Much above or below those ratios and it won't run. Check for any signs of internal fuel leakage or air leakage below the throttle plates and make certain your throttle body is rigged correctly for idle and rpm control.

A leaky vacuum diaphagm in the old Load-A-Matic distributor can give you problems too.
Click to expand...

Mine was leaking out the power valve and thru the power valve control passage which I believe is under the throttle plates and that's why I was having idle problems as well. I could be wrong but the power valve is an easy check that could be done while checking for other leaks around the carburetor base.
 
The puzzling part is that it idled fine at first, then went nuts. I never noticed any sign of the throttle plates sticking. You pull it back, and it snaps all the way forward when released. There could possibly be a big air leak I guess, but it idled fine, then it did kind of a "brumpbrump....brumpbrump... then the next time it started the rpms steadily increased smoothly from normal until I got nervous and clamped my hand over the open carb.
 
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Could there be a massive intake gasket leak? A few of the bolts were actually loose before I started all this. I tightened them back down and hoped for the best. A new intake gasket wouldn't hurt, and certainly might help. In addition to more carb work of course. If I can't iron it out on my own, the carb master is here in town.

Edit, current.

Well, It just ran the longest it ever has, but unfortunately with my hand over the carb with only a small open slit. Another quart of fuel, vanished in starting attempts and idling 2 minutes. I am almost afraid to run it, given how much fuel is dumping into the engine. Is there any possibility at all, that the gravity feed is running too much pressure to the carb? It's sitting on the cowl. Also, once the block warms up the intake might not be sealing correctly. It idles nice at first, then goes crazy after idling a while. That makes me think heat related problem.

Side note: Both radiator pipes started to get warm, so the thermostats are opening at least?
 
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Spray a little starter fluid around the base while the engine is running and see if the idle picks up. But a vacuum leak shouldn't cause it to run away like you said it did.
 
When I went out earlier and started it, I realized the carb base port was open, and plugged it. It didn't change much of anything. It must be just freely dumping fuel to go through that much just idling.

With that said, I will be pulling the carb off to recheck the power valve and float level, etc etc..
 
When you block flow of air into the air intake, you are in effect choking things. This would indicate a very lean mixture since decreasing air intake will richen the mixture.

Rebuildiing a carb requires an understanding of how the instrument delivers fuel and air. Blocked passages will lean the mix way out to the critical point where the choke valve will restore some function although not very efficiently. Leaks will make the mixture very rich to the point it runns rough and black smoke from unburned fuel is passed out the exhaust. Choking would make the mixture even more rich and kill the engine.

If you clean every passage thoroughly and seal up every air or fuel leak, the carb should deliver fuel mixture well enough that adjustments of the idle needles will normally affect the way the engine performs at idle without any choking as long as you start out with nominal mixture screw adjustments.

The old Holley two barrels for flatheads are a little more complex than the Stromberg design but not by a lot. They just use a different metering bar system than Stromberg did.
 
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Don't worry about how much gas your pouring down the carb. It's not metering the gas properly, to the amount of air being sucked in somewhere.......
 
In your first post, you stated that the engine tried to run away on you. The only way that can happen is it was getting more air. Then you said you had to hold your hand over the carb to get it to run. Again there has to be too much air. Where are your idle screws set? Also if you would be using too much fuel, your exhaust should be blowing black smoke. Perhaps you need to take the intake manifold off for inspection.
 
Well, the project is on hold for the foreseeable future. Meanwhile I am completely disgusted to the point where I don't even want to hear the word carburetor right now. I opened the carb and the bowl was empty,but nothing else seemed out of order. I replaced the power valve and got it all back together, when it proceeded to fall off the bench onto the floor, breaking the throttle plate belcrank completely off of the shaft. In a few days when I get over this, I will get going on it again. Thanks for the help, but for now I am taking a break on it.
 
Sad thing is I don't drink much of anything. I might have a beer a month. I had enough of it in my first 20 years of "adulthood" for three people, lol. I kind of take it easy now. I am watching highly improbable kung fu/swordfight movies for the time being, and NBA finals are going in the other room. I amthinking I might give DaVinci a call, and see if they will work on a 94. They're a block away from my work, and close an hour after I punch out. It's worth a shot.


https://www.facebook.com/Davincicarb
 
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