Holley 2280 throttle bushings

thebearded1

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Has anyone ever made bushings for a Holley 2280 throttle shaft?

I just got done rebuilding mine and can't get it to idle and adjusting the mixture screws doesn't help. I noticed gas leaking out of both sides of the throttle shaft once the car was off.

Such a shame because the engine was way more peppy and quick to rev than with the old Holley single barrel
 

thebearded1

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It looks like McMaster Carr has 5/16" shaft bronze bushings in various diameters and lengths. I guess
i will take the throttle plate off and take some measurements and see if they will have something that will work. I'd be interested in any tips from folks that have done this before. I was going to use a drill press vice to drill out the shaft hole in the body for the bushings.
If there is enough meat on the throttle body the smallest bsuhing diameter is for a 3/8" opening. The actual bushing diameter is .376" so if i use a 3/8"(.375") drill bit the bushing should be press fit into place.
 

pishta

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You should drill them with a gun drill so they will be parallel. Press in the bushings and them ream them to the od of the good shafts. You can also glue a toothpaste cap over the flush end to prevent a vacuum leak on a worn shaft end.
 

volaredon

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I've had a Holley 1945 rebushed and a couple of TQs over the years. I miss the days when my buddy worked in the tool room at a nearby factory that no longer exists
 

CNC-Dude

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Keep in mind that drill bits do not make round holes, and can often drill holes larger than the size of the drill bit. A better choice is to drill the hole for the bushings undersize by about .010"-.015" and then use a reamer that is about .0015"-.002" smaller than the od of the bushing so it will have an interference fit so it will have a tight seal inside the carb base and not come out under operation.
 

thebearded1

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after taking the carb apart it looks like re-bushing the base plate may not help as the actual throttle shaft has noticeable wear that you can feel. I tried getting a good photo to show the shaft was worn down not just polished but it was tough.
1669398565404.png


1669398579623.png
 

Bewy

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Although it is hard to tell from the pic, I doubt that that amount of wear is causing the problem.
I have always found 4 bbl Holleys to have a lot of shaft clearance, even when new, compared to other brands, so 2 bbls probably the same.

Worn shafts [ if they are worn ] do not cause fuel to drip. I suspect that you have a high fuel level issue which is causing the idle problem; flooding could be the cause because of leaking n/seat, leaking/binding float etc. You are probably only seeing the external leakage, engine off, because the engine is drawing the fuel IN when it is running.
 

thebearded1

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Although it is hard to tell from the pic, I doubt that that amount of wear is causing the problem.
I have always found 4 bbl Holleys to have a lot of shaft clearance, even when new, compared to other brands, so 2 bbls probably the same.

Worn shafts [ if they are worn ] do not cause fuel to drip. I suspect that you have a high fuel level issue which is causing the idle problem; flooding could be the cause because of leaking n/seat, leaking/binding float etc. You are probably only seeing the external leakage, engine off, because the engine is drawing the fuel IN when it is running.
Thanks for the heads up. I will check that the float isn't sticking and recheck the height.

I can also take some measurements with my calipers of the work and non worn areas of the shaft.

When I tried again the other day before taking the carb apart the engine would run if I reved it up and would idle for a few seconds before cutting out.
 

thebearded1

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Here are the measurements of the shaft
in the center
Unworn .3175
Worn .3140

End furthest from throttle linkage
Unworn .3105
Worn .3070

So it looks like roughly .003" of wear. Would this be fine?
 

thebearded1

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Well the floats were set too low. I readjusted them to 5/16 and now she idles! Still need to adjust the air mixture screws for the best vacuum then make a bracket for the throttle and kickdown cables so I can road test it.

Big thanks to @Bewy for suggesting the shaft was probably fine. I'm always learning with this car and excited to be able to know how to fix this now. It really jumps off idle now compared to the old Holley 1920
 

thebearded1

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now i'm just having an issue finding a possible vacuum leak. I was trying to set the air mixture screws and started at 1.5 turns out and read you should slowly back them out then readjust idle and go till the vacuum stops increasing. Then work them in until the vacuum decreases and back 1/2 turn out. When i started backing them out i got to a point where the curb idle screw was no longer touching the carb base. so I went back to 1.5 turns out and was getting about 16 in Hg at 750 rpms. When i put my hand over the carb top the rpms increased which suggests a vacuum leak right? I used wd40 and checked both sides of the throttle shaft, around the carb intake gasket, where the intake meets the head, the 2 plugs in the intake runner #6 and the egr block off plate on the end of the intake (i used a new gasket with this too)

Engine is a 1971 225 stock, super six intake, holley 2280, timing was at 5 btdc and now is set at 10 btdc
 

thebearded1

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now i'm just having an issue finding a possible vacuum leak. I was trying to set the air mixture screws and started at 1.5 turns out and read you should slowly back them out then readjust idle and go till the vacuum stops increasing. Then work them in until the vacuum decreases and back 1/2 turn out. When i started backing them out i got to a point where the curb idle screw was no longer touching the carb base. so I went back to 1.5 turns out and was getting about 16 in Hg at 750 rpms. When i put my hand over the carb top the rpms increased which suggests a vacuum leak right? I used wd40 and checked both sides of the throttle shaft, around the carb intake gasket, where the intake meets the head, the 2 plugs in the intake runner #6 and the egr block off plate on the end of the intake (i used a new gasket with this too)

Engine is a 1971 225 stock, super six intake, holley 2280, timing was at 5 btdc and now is set at 10 btdc
I sprayed the throttle shaft ends with starting spray and SURPRISE they are the vacuum leak. The throttle shaft from a 318 Holley 2280 should be the same right?
 

Bewy

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I doubt 0.003" of wear is causing any problems. You have an adjustable air+fuel supply [ the mixture screws ] to compensate for variations. That is why it is adjustable.
I tuned my first carb in 1964 & I am still learning.....
I never use a vac gauge for idle adjustment, I tune by ear & feel. You want the highest idle rpm combined with smoothest running. Squirting propellant around any gaps WILL increase idle speed, that is normal.
Getting back to shaft clearance & air leaking past it. There are numerous sources for the air entering the engine at idle:
- PCV valve
- gap around t/blades
- air past idle mixture screws
- the t/slot; air from above the t/slot, around t/blade, exiting on the manifold side.
- leakage past the t/shaft.
So leakage past the shaft is only a small proportion of the total amount of air entering the engine at idle.
I have not found the hand-over-the-carb test very useful & I do not use it.
 

thebearded1

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I doubt 0.003" of wear is causing any problems. You have an adjustable air+fuel supply [ the mixture screws ] to compensate for variations. That is why it is adjustable.
I tuned my first carb in 1964 & I am still learning.....
I never use a vac gauge for idle adjustment, I tune by ear & feel. You want the highest idle rpm combined with smoothest running. Squirting propellant around any gaps WILL increase idle speed, that is normal.
Getting back to shaft clearance & air leaking past it. There are numerous sources for the air entering the engine at idle:
- PCV valve
- gap around t/blades
- air past idle mixture screws
- the t/slot; air from above the t/slot, around t/blade, exiting on the manifold side.
- leakage past the t/shaft.
So leakage past the shaft is only a small proportion of the total amount of air entering the engine at idle.
I have not found the hand-over-the-carb test very useful & I do not use it.
-I guess i could try plugging the PCV port on the carb. it is hooked up to an early valve cover with the ribs that doesn't have the modern PCV with the grommet. it has a bent tube of metal with a check ball inside.

-Is there anything that can be done about the space around the throttle blades? I did notice some slight light coming through when i put the shaft back in

-no sure about the t/slot or how to check it

-would adding an o ring between the carb base and throttle linkage and another on the opposite side with a washer and small spring help with throttle shaft leakage?

I can get it to idle at 750 but it's no were near as smooth as the 1 barrel carb. the 1 barrel carb I could get to idle at 500rpms but couldn't get any lower because the curb idle screw wasn't touching anymore.

It still seems to be running rich as my eyes get itchy after running it in the garage with the door oepned and strong fan circulating air. it also stinks too
 

thebearded1

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i did notice the barrel closest to the valve cover was puddling gas on the butterfly while warming up but stopped once it warmed up
 

Bewy

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Do not delete the PCV. It keeps the engine clean internally. All carbs that use PCV are designed for the air flow they add. Make sure the PCV is not gunked up. It should rattle when you shake it. If blocked with gunk, it might let in excessive air & be contributing to the problem. Have you got another one you can try?
T/slot, built into the carb, nothing there to adjust.
The o ring idea is good in concept but I think it would wear out quickly with the constant shaft movement.

This carb does sound like it has issues if 750 rpm is the lowest idle rpm you can get with speed screw backed out. Is the intake new or have you used an adapter for 1 to 2bbl?
 

CNC-Dude

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If you have wear on the shaft, you also have equal or more wear in the base plate. One can't have wear by itself, so combined you can have enough to be considered excessive. I would agree that .003" alone wouldn't be a problem, but you have to consider the wear the base plate has as well.
 

thebearded1

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If you have wear on the shaft, you also have equal or more wear in the base plate. One can't have wear by itself, so combined you can have enough to be considered excessive. I would agree that .003" alone wouldn't be a problem, but you have to consider the wear the base plate has as well.
i agree but didn't have a way to measure how much wear there was in the hosuing since i didn't have an area to measure an unworn section
 

thebearded1

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Do not delete the PCV. It keeps the engine clean internally. All carbs that use PCV are designed for the air flow they add. Make sure the PCV is not gunked up. It should rattle when you shake it. If blocked with gunk, it might let in excessive air & be contributing to the problem. Have you got another one you can try?
T/slot, built into the carb, nothing there to adjust.
The o ring idea is good in concept but I think it would wear out quickly with the constant shaft movement.

This carb does sound like it has issues if 750 rpm is the lowest idle rpm you can get with speed screw backed out. Is the intake new or have you used an adapter for 1 to 2bbl?
the intake is new and i checked the mounting surface with a straight edge, i mounted the intake and exhaust together using remflex gasket. also used remflex for mounting intakes to the head. I figured it wasnt the pcv as i didn't have any issues with this valve cover when i had the holley 1920 on there. That carb cracked and leaked which is why i made the switch.

carb was not too dirty inside and i used a mikes carb parts kit specifically for the number on the carb
 
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