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  #16 (permalink)  
Old 06-12-2016, 09:38 AM
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Before anything on carb tuning always double check that your timing is correct for your engine build and that timing is not coming in to quick or not having enough initial timing at idle as it will cause tuning issues as well. Also make sure you ignition system is up to code as any issues there can cause tuning issues as well. I go by the one two three method.

1. Check and correct timing
2. Check ignition system from distributor to plug wires and spark plugs.
3. Set carb for initial start up with a note book at hand with your starting settings written down. Write down what any changes does.


You should never have to use the black spring in order to not have a bog when hitting the throttle. From my tuning experience the yellow and purple springs give the best results and just about work on any vehicle type. That like mentioned above is a accelerator pump circuit issue that needs tuned. When looking at the charts it can be kind of confusing at least it was for me when I first learned how to tune a holley. First thing before anything only tune one area of a carb at a time and make notes where you started and jot down what affect the change had and if it does not work then you can go back to your notes to start over if need be.

On the shooters they have number sizes and if say you have a number .028 shooter it will give lesser of a shot while having a longer duration during throttle travel. Now any time you change shooters you always need to go up about three sizes to notice any difference.

For example going up to the .031 shooter it will give a bigger shot when opening up the throttle but less duration across throttle travel. On the pump cams for example the pump cams function in a similar way the pink cam for instance will give a lesser shot while opening the throttle and have a longer duration across throttle travel.

Going up to a mid range pump cam such as the orange one for example it will give a bigger shot while opening the throttle but less duration across throttle travel. Then on the pump cam on the side of the throttle there is a number 1 and 2. On the number one setting it gives the shot instantly and on the number two position it delays it just a hair while gas is still shooting out the shooters.

I start with shooters first and if going up in size does not change anything then I go back down as you don't want a big shot just to cover up a bog and be pig rich as that is only a band aid tune. Then if going up does not work I go back down to the size I started with and then go to a middle ground pump cam such as the orange one and then try again and see how it feels and does. What your looking for is a nice quick lean snapping of the throttle with out any lag or bog. If it seems kind of on the heavy side and not as fast but yet still no bog then its a little to rich.

It takes time and the best way to tune a holley is first tune the idle circuit such as the mixture settings and also making sure you have the correct butterfly position for a good idle without having the transfer slot opened up to much or to little which can cause bogging as well. After adjustments are done there then take for a test drive and see how part throttle acts and tune the accelerator pump circuit from there.

After getting part throttle with a clean shot then move on to wide opening of the throttle and see how the shot works then and make sure there is no bogs. After that is done then proceed to normal cruising and driving to see how your jetting is doing by looking at the spark plugs. Wide open tuning for secondary jets is a little more tricky if you can't take to a track but I just go by plug reading and I get within the ball park.

Below is a good link to help you understand how a carb works with each circuit. What you want is to go from each circuit to another with a smooth transition.
Carburetor Tuning the Scientific Way

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Rodder steve (07-01-2016)
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  #17 (permalink)  
Old 07-01-2016, 05:56 PM
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Rebuilt the carb... It runs good at higher rpm but cannot get it to idle now. Float level is good, all vac lines blocked. Thinking...thinking. I'll check the board posts for more info.
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Old 07-01-2016, 06:05 PM
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Let's see, things to check....
Check balls in the accelerator pump?
Does the idle circuit work? Is it adjustable (does the idle quality change with the screws?
Does it surge or run smooth at cruise speeds?
Does it accelerate well from a stop? How about from road to highway speeds?
Proper gaskets used in and under it?
Is it possessed? (Demon carburetor)
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Old 07-01-2016, 08:04 PM
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Quote:
Originally Posted by OldTech View Post
Let's see, things to check....
Check balls in the accelerator pump?

It has no balls, just a little rubber thingy.

Does the idle circuit work? Is it adjustable (does the idle quality change with the screws?

Nope.

Does it surge or run smooth at cruise speeds?

Have not tried to run it down the road, does not idle well enough to get it out of the garage.

Does it accelerate well from a stop? How about from road to highway speeds?

Same as above answer.

Proper gaskets used in and under it?

Rebuild kit from Autozone.

Is it possessed? (Demon carburetor)
Probably.

...

Last edited by Rodder steve; 07-01-2016 at 08:10 PM.
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Old 07-02-2016, 09:49 AM
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Does run smoothly at high idle. Removed idle screws and blowing carb cleaner and compressed air through and it blows out into carb.
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Old 07-02-2016, 12:20 PM
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It could be the idle air bleeds. What did you use to clean the carb when building it and did you use air to blow out passages?
Using a generic rebuild kit? Did the gaskets match properly? (and exactly?)
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Old 07-02-2016, 04:26 PM
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Quote:
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It could be the idle air bleeds. What did you use to clean the carb when building it and did you use air to blow out passages?
Using a generic rebuild kit? Did the gaskets match properly? (and exactly?)
Just put back together after another cleaning, rough idle now, will kill when put in gear. Noticed at idle gas coming from right side nozzle only till I give it some gas. Used carb cleaner to squirt through the passages and used compressor to blow em out. Gaskets all seem to line up hole for hole. Carb kit was for 4160 holley. Ran better before I put the kit in.
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Old 07-02-2016, 05:02 PM
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Are you meaning that you have fuel dripping out the shooter only on one side while not giving it any gas and once you do then you have it coming out both sides as normal? I have read somewhere before to where a guy had gas dripping out just one nozzle at idle on his holley carb and putting new gaskets in it along with cleaning it up still did not fix anything. I can't remember what it was but he did get it fixed. To me the primary metering block has a lot of different things that can go wrong if the casting itself goes bad inside from years of corrosion or just plain porosity issues can wreck havoc on trying to fix weird not normal carburetor things that can happen from time to time.

I had an issue before to where on a quick fuel carb by putting the choke on it would pull fuel from the primary boosters when engaging the choke but when it gets any air its supposed to stop and only be pulling from the transfer slot well mine would just keep on pulling fuel even when opening up the choke all the way. I messed with it and messed with it and could never get it to work right. I finally sent it back to quick fuel and they never did tell me of what they found and they replaced the primary metering block and such but I never did hook it back up to see if it was a block issue with some type of fuel siphon issue. My holley's and other quick fuel brand carbs never gave me any issues like that. I know that is not what is wrong with your carb but its just an example of how weird things can happen and changing things never fixes it. Also maybe your carb base gasket might not be right or leaking somewhere and not sealing right and its causing some of your issues and it to not run right. If you have another metering block you could try maybe do that and see how it does. I have had issues in the past with a holley that had a bad primary block out of the box to where the thing would never run right unless you kept giving it gas all the time and when not doing so it would just fall on its head and always want to quit and when I put a different carb on my engine ran just fine. It was a brand new one too. Hope you get it running.
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  #24 (permalink)  
Old 07-02-2016, 05:50 PM
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My metering block looks brand spanking new. I have another base gasket, think that's the next thing I'll try.
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Old 07-02-2016, 06:24 PM
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Bummer... changed out base gasket, no change. Took idle mix screws out and started her up, could keep it running at high idle but no idle.
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Old 07-02-2016, 08:39 PM
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How old is your demon carb? It seems like to me either you have a vacuum leak somewhere even though you have everything blocked off or there might be some crud in your metering block or possible air bleed blockage. Now if there is no vacuum leak of any sort and the metering block is free of any debris then something has to be limiting fuel flow somehow on the idle circuit since you say you can drive it good and also can rev it fine if I read correctly. If not being able to get it to idle speaks fuel starvation of some sorts at idle and either air is entering somewhere or something just went crappy with the block which should not happen but I have experienced it before. Do you have a spare holley primary block laying around that you can try and see how it does? Also is your timing correct as not enough timing can cause a lot of these type of issues with it being hard to keep and idle as well. I have seen where folks took apart there carb and when putting it back together it somehow warped the main tower some and it would not run right and they had to file it down for the gasket surface to reseal again. If you have a straight edge put it up against the tower and measure straight across and diagonally corner to corner both ways. You want no more then .006 or it might leak and not run right. I just recently did a carb tower and bought it used from ebay and it was over .010 and I had to take a sanding block and smooth it down and got it to within .001 but took my time.
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Old 07-03-2016, 10:52 AM
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Thanks for all the helpful hints. Got her figured out. All had to do with me getting fancy. Yeap, I had to have those cute little nuts and washers to bolt the carb down with (polished). What I didn't see was that those washers were a little thinner that the old washers. The nuts were bottoming out at the end of the threads on the studs leaving the carb slightly loose on the manifold still. Once I added the old washers and put the fancy ones on top of those then the carb bolted down Jim Dandy and fine. Idles now.
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Old 07-03-2016, 03:29 PM
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Awesome deal and I am glad it was just something simple and have been there before and thought the worse case scenario and it turned out to be something simple. Glad you got it.
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Old 07-04-2016, 08:47 PM
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Quote:
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Awesome deal and I am glad it was just something simple and have been there before and thought the worse case scenario and it turned out to be something simple. Glad you got it.
Awful lot of mechanical rust on my mechanical brain but I have what some of these newer cars have... it's called "limb home mode".
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