Carburetor Rebuild Tip, Inlet Needle Clips

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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by tomo »

I used to adjust one needle for the highest vacuum and then adjust the other one for the highest vacuum. Then I read a Holley manual on tune ups and changed my way of doing it. This procedure allowed me to set the idle speed at the factory recommended 450 rpm and still be able to drive the car without it stalling at stop lights.

The procedure in the Holley manual is to: set the needles to the initial setting, connect the vacuum gauge, start the engine, set the idle speed and timing to factory specs, Then turn one needle in 1/4 turn and observe the vacuum reading. If it is higher, turn the other needle in 1/4 turn. Then adjust each needle 1/8 turn until the vacuum starts to drop, then back off the needle that you adjusted last1/4 turn and the other needle 1/8 turn. Doing it this way assure that both primaries are set the same.

If the initial 1/4 turn lowered the vacuum reading back it off 1/4 turn and then adjust each side 1/8 turn at a time. If there is a significant (50 rpm) increase in rpm, readjust the idle speed before proceeding further. Throttle position will affect the adjustment. Idle speed and initial timing will affect the throttle position.
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by TonyC »

Good info there, Tom. I think I may just try those tweaks in the next couple days, see how that changes things. I'll admit, I'm still in the learning stage when it comes to adjusting a carburetor; it seems that rebuilding one is easier. So any good advice is welcome.

Question: I'm presuming the engine needs to be warmed up first for those adjustments to have proper effect?

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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by jon schapiro »

All adjustments except cold high idle are performed at engine operating temperature.
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by TonyC »

I thought as much. Got it; hoping to do that in the next day or two.

---Tony
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by 1Bad55Chevy »

TonyC wrote: Tue Nov 29, 2022 3:06 am I thought as much. Got it; hoping to do that in the next day or two.

---Tony
On a completely different topic...

Why are all your post at 0400 hours? Once retired your not supposed to be waking up at "stupid dark thirty" lol
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by TonyC »

:lol: That's because I don't wake up at stupid-dark-thirty anymore; I'm already awake at that time. I've always been a night-owl my whole life, more active at night (don't ask how I was able to change that habit for Army service, because I don't know); so it's nice to no longer force myself to sleep by 2200. When my neighbors are getting up and preparing for PT formation, I'm just then starting to wind myself down. My first wake-up might happen between 10am and 11am, then my second wake-up occurs about 2pm. That can make it hard to visit the auto center on days I may need to...but, gotta take the rough with the smooth, right? :mrgreen:

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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by TonyC »

Well, all, bumping this thread to report that I finally did that carburetor swap today, taking off the one I had been using since the engine surgery and putting on the '66-specific one I rebuilt last year. It is still too early to specify how much of a difference that made, but I did notice immediate differences. When I started up the car (which took a couple hours longer than I thought, as the battery drained just enough to prevent a fire-up after pumping fuel into the empty chambers), the difference in cold idle was like night and day! Even without having made the fine-tweak adjustments yet and my vacuum needle reading only 14", the engine was as smooth as anything, and no new soot deposits on the ground! I did a drive around town, and I swear the fuel gauge's needle did not drop nearly so fast as it had been! When I got home, I did the fine-tweaking of the screws right to the spot where I got the best vacuum reading I could muster, which was just above 17". On a related side note, my vacuum gauge is old and reads lower than the actual vacuum being pulled, from 1" to 3" (the latter difference I noticed with the gauge on my vacuum pump, when that still worked); so I'd say the actual reading is probably closer to 20". After doing the adjustments, I did a second roll around town, and the engine felt different. Even the exhaust smelled different...and the needle was at the 1/4 mark when I shut him down, from at the half mark when I first started up. Having gotten used to the way the needle would drop with the other carburetor, it would have been almost at the Empty mark after the same amount of driving.

I think it will be a bit of time before I can report actual fuel economy figures on this new carb, as I still want to run a bottle of fuel-system cleaner through with the next fill-up, then I'll have to do a bunch of driving around on that tank and get another fill-up to calculate mpg's...but for right now, everything looks very promising.

---Tony
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by SoCal61 »

Hi Tony, just wanted to thank you for the good info on the carb rebuild and fine tuning. About to tackle rebuilding the carb on my 61. How’s your running now after several months?
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by TonyC »

Hi, SoCal! :smt006

I would say it was a success. Aside from a slightly longer hot-crank time, I have not had any issues since I did that rebuild...well, there was one vapor stall-out I suffered, like about a week or so ago; but I was able to overcome that and fire back up, and when I poked around I saw the ignition timing had retarded itself, which likely contributed to that. I adjusted timing, no more problems. And, the exhaust is as clean as it can be; no more soot stains on the pavement, and the ones I had left are long-since washed away. It even seems that the starter turns over better since that swap, and the fuel economy has gone back up to double-digit status.

Good luck to you on your rebuild project! It shouldn't be quite so bad, as you'll have only two barrels to deal with. Follow the manual, and you should be okay. :smt023

---Tony
Last edited by TonyC on Fri Jul 14, 2023 7:56 pm, edited 1 time in total.
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by Lee »

Welcome SoCal! So has your engine swapped out the original 2V ABD for a 4V AFB like on Tony's?
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by SoCal61 »

Thanks again Tony.

Lee, I have the original two barrel. I paid $85 for a rebuild kit from Mike’s. Now I’m wondering if it’s worth getting a new carb altogether. Trying to see what would fit. I have a performer 4 bbl that may work. Any suggestions?
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Re: Carburetor Rebuild Tip, Inlet Needle Clips

Post by Lee »

The Carter ABD is a great carburetor. Keep it. Mine is still the original - rebuilt a few times - and aside from the leather accelerator pump tending to harden over time in ethanol fuels (you can read my thread from a few months ago for a solution to that), it is dead reliable, and perfectly jetted and calibrated for the 430. You'll never be "spot-on" if you go the Edelbrock route. Your plugs will always look textbook, and you'll typically pull down 16 mpg on the open road.
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