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Discussion Starter #1
Might be a shot in the dark here. I have a non stock Holley #80457-2 4 bbl carb and I need an accelerator pump diaphragm - stock is fine. Mine is just not squirting at all and has a small leak/weep. I plan to pull it apart and look/clean it and figure I'd be smart to have a diaphragm handy I have found 30cc and 50cc with the 50 being for hotter engines - I just need the 30cc. I think all of Holleys pumps are the same size and should fit but I have also found different parts numbers so I'm not sure which I should get.


Anyone know Holley carbs????


Thanks


LBM
 

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Need to also make sure the little one way checkball is free or some have a little mushroom valve in the base of the float bowl
 

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Greg has one of the issues nailed....
Accelerator pump check needle under the pump nozzle often flash rusts to it's seat and no fuel will come out.
I typically oil the needle and seat when restoring a Holley.


To fix remove nozzle, get a very sharp scribe and try to push the needle left and right. Be careful not to ruin the threads in there. Push accelerator pump and see if fuel comes out (be careful it can come out with a lot of force, especially if it is stuck).
Fix the problem? yes/no?
If yes, good.

If no, remove metering block and bowl, shoot high pressure air into pump hole in main body face. Placing a rag over the main body keeps fuel and the needle from firing out at 150mph.


Other possibility, if you have an umbrella check under the pump nozzle it may have failed. If this happens it just pushes the fuel back into the bowl.


You can tell the difference by pushing the accelerator pump by hand... if it pushes easily it's probably the umbrella seal, if it is rock hard it is the check needle. If the pump diaphragm failed it will typically just leak.


Drew
 

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Discussion Starter #6
OK That answers a lot. The pump does not move and is leaking a little bit. I found a diaphragm for under $5 with free shipping so I ordered it. I'll start with taking off the bowl and cleaning out the stuck shaft and looking at the needle and umbrella.. It's a brand new carb taken off a Chevy crate engine and sat on the shelf for close to 15 years - I suspect the needle may also be stuck. Thanks LBM



Greg has one of the issues nailed....
Accelerator pump check needle under the pump nozzle often flash rusts to it's seat and no fuel will come out.
I typically oil the needle and seat when restoring a Holley.


To fix remove nozzle, get a very sharp scribe and try to push the needle left and right. Be careful not to ruin the threads in there. Push accelerator pump and see if fuel comes out (be careful it can come out with a lot of force, especially if it is stuck).
Fix the problem? yes/no?
If yes, good.

If no, remove metering block and bowl, shoot high pressure air into pump hole in main body face. Placing a rag over the main body keeps fuel and the needle from firing out at 150mph.


Other possibility, if you have an umbrella check under the pump nozzle it may have failed. If this happens it just pushes the fuel back into the bowl.


You can tell the difference by pushing the accelerator pump by hand... if it pushes easily it's probably the umbrella seal, if it is rock hard it is the check needle. If the pump diaphragm failed it will typically just leak.


Drew
 

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Yup sounds like needle stuck, and with no where to go the pump can tear/leak. You got her on the run.....




After you get it all back together and fixed up, make sure to recheck pump/spring/lever clearance. Those metal pump arms do bend, and when pushing on fuel with no where to go it can bend if the spring is firm enough.
I set a slight preload on the pump, old style pump arm I set the spring at 1/2inch, newer style I set at 5/8inch (spring length)
I set preload by bending the arm as needed. As long as the arm isn't bottoming out you are good to go.
 

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Oh, and I do a LOT of Holley carbs, but I don't often come to this forum anymore.
If you need any other help, either PM me, or msg me via my restoration page on Facebook "Air Fuel Spark" I document some builds there and post tips, etc.


I don't mean for that to sound like an advertisement, it's just a super easy way to contact me since I monitor it whenever I have cell service.
 

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Discussion Starter #10
That is a good idea - I did tighten up the nut to try and get it to pump - probably did bend it - You are talking about the spring inside on the diaphragm correct - not the spring on the pump shaft-lever?



Yup sounds like needle stuck, and with no where to go the pump can tear/leak. You got her on the run.....




After you get it all back together and fixed up, make sure to recheck pump/spring/lever clearance. Those metal pump arms do bend, and when pushing on fuel with no where to go it can bend if the spring is firm enough.
I set a slight preload on the pump, old style pump arm I set the spring at 1/2inch, newer style I set at 5/8inch (spring length)
I set preload by bending the arm as needed. As long as the arm isn't bottoming out you are good to go.
 

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no he means the spring on the arm. the one inside only returns the the pump to fill. the oe on the arm is a duration spring. it controls how long the shot of fuel lasts
 

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Discussion Starter #12
OK - so to adjust it is a factor of stretching it if you want the 5/8" or squish it if it is more then 1/2" or is it changing springs. Not understanding I did tighten down the spring to coil bind and I suspect it might be sacked out a bit. If it is sacked I can stretch it a bit to make it work. ???



no he means the spring on the arm. the one inside only returns the the pump to fill. the oe on the arm is a duration spring. it controls how long the shot of fuel lasts
 

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Discussion Starter #13
I think I figured it out - set the spring length via the nut @ the bottom - tighten or loosen up. Still learning about Holleys



OK - so to adjust it is a factor of stretching it if you want the 5/8" or squish it if it is more then 1/2" or is it changing springs. Not understanding I did tighten down the spring to coil bind and I suspect it might be sacked out a bit. If it is sacked I can stretch it a bit to make it work. ???
 

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if you made the spring solid, stomping the gas would break something. you need the spring to distribute the load to not hydrolic the sys
 

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Spring lever/arm info:

Holley tells you how to set pump arm clearance in a very confusing way. Seems to lead people into thinking you need .015 at idle, this is incorrect. You need slight preload on the pump so that the instant the throttle is touched the pump is in action.


What you should see is .015 at wide open throttle.
With some pump cams this isn't possible, but on the majority of them like the white and orange cam this is easy to set. Some double pumpers using the blue cam run into where there is zero clearance at WOT, and that is ok too, but it certainly makes the setting critical.


In truth if you stomp on the throttle the spring will compress because there is fuel in the pump and it takes time for the fuel to fire through the accelerator pump nozzle.
Assume all of these are 30cc pumps, we won't address the larger 50cc here.
A given nozzle size like .031 or .035 fires a large shot quickly.
A smaller nozzle like .021 or .025 fire a smaller shot, but for a longer amount of time.
Obviously there are variables like the amount of preload in the pump, or the cam being used, but the pump itself is a static size.
The spring under the pump is to press the pump back down so it refills for another shot.


Back to the lever arm spring.....
Why I give compressed height for these is because these sizes give you the best clearance when the throttle is stabbed and the spring is compressed while the pump is trying to push that fuel through the nozzle. If the spring is too long it makes it hard to get the settings right, if it is too short it'll bottom out and as Extech so wisely stated, It'll break stuff.


There are two common arm/springs for a 30cc pump, the old style I set at 1/2inch, the picture is below:
IMG_0777 by Drew Pojedinec, on Flickr


The new style arrived sometime in the early 70's and I like to set as 5/8inch spring length. In the picture below I'm getting it towards that setting.
IMG_0778 by Drew Pojedinec, on Flickr


These lengths are not essential, but they are a very good place to start.
Once the spring is set, the cam is in place, etc, you may find you have too much or too little preload.
This is set by slightly bending the pump lever where it contacts the cam.


and remember, when changing idle speed, your pump setting and preload WILL change. It will be slight, but it is something to recheck after adjustments are made.


Drew
 

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Discussion Starter #16
Again very good info and the photos make it clearer. The .015 clearance which is achieved with the 1/2 - 5/8" spring measurement is basically pump arm free play and would be measured between the pump arm and the head of the spring bolt at WOT. Correct? For my needs I probably don't need to take that measurement but measuring the spring would get me in the ball park and be sure there is some free play between the arm and nut @WOT to be sure I haven't bent the arm. My spring set up is post 1970 and looking at the photos the spring is probably thick enough that I haven't damaged it - might need to stretch it a bit. Definitely need to pull the carb off, so I can pull the pump nozzle and clean it , the needle and passage - don't want to fumble finger it and drop it down in the engine- and square away the pump. Should get it fixed.



Thanks again to every one - printed this one off - worth saving.


LBM
 
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