Fuel float struggle

Hi trever

can you help me understand the operation of a choke? I have a Holley 4150 heat choke 4bbl 425cfm vac secondary.

If I can get the engine running properly. And the engine is up to temperature.. If I dial the large back choke cap on the side of the carb loosen or tighten. Would that change the idle speed of the motor?


I'm about ready to tow out the car to a mechanic

my friend tells me it an air problem not fuel. Since we got the engine running at high again ( its only base speed) and forced the choke place completely closed. It continued to run. No change in high idle.


Thx
lawrence
 
The black dial on these carbs houses a bi-metallic spring which reacts to heat supplied either through electricity when the ignition is switched on, or in older models via heated air plumbed through a tube attached to the exhaust manifold (hot air choke). When the spring is cold, the tension created tends to force the choke butterfly plate closed. As heat is applied to the spring, opposite tension allows the plate to open at a slow and steady pace until it reaches full vertical. This is a timed event that takes roughly five minutes from start to finish. As long as the heat source remains, the plate will stay open. The dial is what allows one to adjust the spring tension which controls how Rich or lean the choke setting is and thus the overall duration from fully closed to fully open. The base setting is smack in the middle of the adjustment range. In the dead of winter, it is a common practice to adjust the dial one or more notches towards the Rich direction as engines tend to require longer warm up time in extreme cold. The adjustment often goes back to center or even a notch lean in the middle of summer.

The dial has little if any influence on the applied choke fast idle speed. There should be a small set screw on the same side of the carb as the dial, but behind it and facing down at a slight angle. It can be difficult to see with the carb on the engine and without some head contorting. Anyway, this screw sets the tension applied to the graduated fast idle cam. The general idea is to set it so that it holds the engine speed at roughly 1600 rpms on initial cold start up, which helps keep a cold engine from stalling out. The fast idle cam is graduated, so that as the choke plate opens, the fast idle speed can automatically step down roughly 200 rpms per notch. The fast idle speed can also be cancelled manually ahead of schedule by blipping the throttle, which should instantly drop the engine down to a curb idle speed of roughly 7 or 800 rpms.

A closed choke plate should snuff out all but the coldest of engines. If a warm engine continues to run on with a closed choke, then it is sucking air in from another other location...aka vacuum leak. This jives quite well with the direction our conversation has been going in for the past x number of months, as also evidenced by your wildly erratic vacuum needle. Now the source of this vacuum leak could be outside of the carb ie power brake booster, ruptured vacuum line etc...or it could be part of the carb, ie leaky gasket, incorrect gasket, internal orifice that should be plugged remaining open to the atmosphere etc...or both!!! So the problem could conceivably still be within the carb.
 
Hi "scoutboy74"

thanks so much for the explanation on the choke idle repairs. I have e-mailed my todays 'findings' with a friend and immediately received a computer 'on vacation' response that the "tech" will not be back to work until 11/11/2013. Ug!

Okay so I will wait a week to see if they can find what I think was a mistake by the parts store in giving the wrong kit. I dunno? I will post what I expect their brief reply to be. I'm glad I'm not working on this car for a customer!

Warmly
lawrence:smile5:




http://www.Holley.com/data/products/technical/199r10013rev.pdf





Hi guys



to follow up. I had friend come over and help diagnose my problem. After running the engine he seems to fell that there is a gas problem. Mainly a constant "idle" flow not existing in the carburetor. Who you please look at the following you tube video of my engine and help answer a question



post carb rebuild loping engine - youtube



As you can see the engine will run without intervention on high idle. But my buddy seems to think that as we used starter fluid in spurts to keep the engine from dying. It was actually running on gas from the occasional throttle pump I would give the engine.



So can you help me buy the correct metering block gasket? In my first rebuild attempt I failed: why. I reopened the carb to find I had used the wrong gasket in the kit. And replaced it with what should be a functioning gasket





if you go to the forum site and scroll all the way to the bottom you can see photos of how I learned of my mistake and what I did to in my gasket selection.



http://forums.IHPartsAmerica.com/basic-tech-questions/9019-fuel-float-struggle-2.html





Yet now with the photo graphed gasket in place. I think I did things right and should not have the idle problem I have!. I have cleaned the carb very well and find strong flow on all ports and jets, openings etc. So, would you look and see if I have been given the correct gasket by the auto parts shop? Is it possible to flip the gasket incorrectly?



Because there are ports on the metering block that seem blocked by this gasket. But I think that this is intentional by design? Or am I wrong?







Warmly,





lawrence
b.a. M.a.
 
Hi trever


my reply from Holley.com techs

the proper metering block gasket number is 108-89-2. One of the metering block dowel pins would not line up if the gasket was reversed . The sound of the engine in the video would still indicate a vacuum leak or a restricted / blocked idle feed. I am assuming the timing is correct. . the metering block you have uses an idle feed tube in the main well . if it is contaminated it can be a little difficult to clean and or confirm that it is clean . make 4 tubular spacers that will allow you to bolt the metering block to the main body with the bowl off . use the small plastic tube on a can of carb cleaner and spray cleaner in the idle discharge ports in the base plate with the mixture screws out about 2.5 turns and see if you get a consistent discharge from the main well with the jets removed . [/I ]



well I did not really like the reply given to my question from Holley techs at Holley.com . I did not get a second reply why I should build spacers and not just hold the metering block in my hand .
so I went one better and just took the carb apart and did a youtube video to show that all of the holes are clear .

https://www.youtube.com/watch?v=78d...ks labor thanks. Warmly, laurence frazee
 
Have some keep the truck running while you adjust the float level using the big nut on top of the bowl. Turn the screw in until you get now flow out of the over flow unless the the vehicle is shaken.

Until the float level is set correctly all the other adjustments are a waste of time. Start with the big nut loose and the screw in the middle tightened down by about 1 full turn.
 
Thanks

okay help me with theory. If the fuel level in the bowl is set perfectly. The accelerator diaphragm will pump fuel into the bowl, the excess pressure will force fuel into the jets and into the carb/pistons.

Can the heavy foot pumping of the throttle over flow the fuel bowl level too high? Or will it just escape.

Thanks
lawrence
 
The fuel pump fills the bowl with the level controlled by the float needle. The accel pump does not add fuel to the bowl. It forces fuel from the bowl through the nozzle squirters and into the combustion chamber. Excessive throttle pumping prior to the engine being started will flood the combustion chamber and the engine will start poorly if at all.
 
To expand on what scoutboy said, the accelerator pump pumps additional fuel into the air stream above the venturi's and throttle plates. Fuel is drawn out of the fuel bowl through the jets by the venturi effect.

To simulate the venturi effect imagine having your mouth just above a straw and sucking a mixture of coke and air into your mouth from a full cup. Now imagine the cup is almost empty. It takes more suction to lift the coke farther up the straw right? What does this do to your coke to air ratio. This why having the correct fuel level in the carb is so important.
 
Okay guys


thanks for the help I think will take "fd"s advice that my loping May be caused by the float level. And excess fuel is a no brainer as well. I will empty the fuel bowl by syringe engine off. And then dial down the needle severely. Then crank the engine to fill the bowl and maybe start.

Then site check the level. Repeat the process until I can get it running or get a proper level. Which I thought I was at anyway. ( setting by eye with bowl off )

it will take me time in my schedule to do this maybe next week

thanks!!!
Lawrence
 
Hi guys


well I broke down and took the carb to the local carburetor shop here in concord. CA. To a professional business mechanic specializing / working on carburetor's for 30 years he claims. He placed my carb on a shop engine and sounded like he reproduced my problems exactly. In his quote for work he mentioned the problems I was a having with my engine.



So I am confident that my engine and it's vacuum system is not at fault. Yet for the cost of 299.00 dollars he would set the seeking idle both high and low idles. Clean the bowls. Repair the choke assembly. Etc.. Now at the choke assembly comment. I think he was just rambling. Maybe adjust the screw.


The assembly has been virgin since purchase and not at all damaged. So for that high a cost I could place my investment in a new replacement right off the shelf. For 371 bucks


Holley 0 1848 1 4 barrel carburetor | ebay



Now of course when I stopped by I talked to assistant and dropped the carb. So I don't know what I'm into the carb for the initial look-see also.


He mentioned that a new carb off the shelf would not be plug and play and need adjustments.... Well I remember this carb at purchase was pretty easy years ago.

He did mention he could get the work done in a day. Which makes me wonder how difficult the problem is!
So what is the recommendation for the guys on the forum site. Sell my junk carb on ebay for pennies and re purchase or.... Spend the dough on this one with a six month guarantee.



Ouch
lawrence
 
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Well it looks like it's down to spend the dough or learn how to do it your self. On the bright side, you will be all set with alcohol resistant components.
 
Man that seems like a lot of cabbage for a pro carb overhaul. Likewise it goes against the grain to shelve a carb that is almost certainly repairable. I get that you're feeling boxed into one of these two options. I know you took a stab at rebuilding it once yourself and it didn't turn out right. I just can't see paying someone else that much money to work on a used carb. I guess if the gun was pointing at my head and I had to choose either option a or option b and there was no other earthly alternative, I'd have to pop for the new carb.
 
Well guys


I went for the rebuild on the carb instead of a new carb from Holley. Bad decision I know.

But putting that aside. I get the carb back from the carb service rebuilder and it looks good as a visual inspection. I put the unit back on the engine and I get the same problems I had before.

The exceptions are that it will start without priming the pump. And its levels are all set. Says the mechanic on his shop engine.

It starts with the choke plate closed and I get the engine water temp running up to hot but the engine heat just barely up to hot to the touch. The choke is obviously not opening yet,. My problem is that the idle revs up and down again as before. I have to stomp on the pedal to keep the engine from stalling at the low point.



I gave up after three minutes out of concern and would like to ask for input

it is more sensitive now but I need help to guess the problems before I call the rebuilder for help/advice or a return.

I wonder if this could be related to the timing. In the last 12 years I have not touched the timing. I started this problem when I open the unit. I have made no these changes since then. I replaced the rear tank which means new gas . The current filter is amber but clean and new. The fuel pump gives me 4-6 pound s psi measured by meter gauge. Measured from a splice point after the filter before the carb. Pulling from a gas can at the bottom of the engine. This filter is only partly filled with gas and remains that way. I was told that was not really a problem.


Could this be related to the new gas or does this sound like a vacuum problem? I have had the same distributor on the car in the last 12 years and its been rebuilt long ago.

Any help is appreciated.

Warmly

lawrence
 
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You say the rebuilder has a test engine? The begged questions in shouting from the rooftop loud all cap letters are: did he run the carb on the test mule after servicing before he sent it back to you? That would be a natural no-brainer if he was set up for it. If so, how did his test mule run with your freshly serviced carb on it? If it ran crappy on his engine, he wouldn't then send it back with his blessing as if it was as good as new if it in fact wasn't, would he? For that much money, it should be as good...no better than new.
As for your timing, while it May not be dialed right to the gnats ass, if the engine fires up quickly without excessive starter-cranking, then the timing is reasonably close and therefore not far enough off to be causing these issues.
 
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