Carb mixture adjustment

Tech tips and how to's

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Linda
Fraternal Den Mother-RIP
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Joined: Sat Nov 05, 2005 11:37 pm
Location: Los Angeles
Model: 1500/1600
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by Linda »

If you want absolute accuracy, get a Gunson Colortune.
Why not all of the above? Perhaps in the beginning when you are just trying to get your car running, anything will do. Then you might begin to see that floats, gaskets, fuel valves, banjo bolt filters, needles, nozzles, dog bones, accelerator cable, linkages, butterfly plates, and vacuum leaks mean something..... Time to upgrade like you tend to do anywhere else on a classic. As one person stated, classic cars tend to be over maintained vs the grocery getter.... You need tools to do that, so, a Unisyn, Colortune, digital caliper and credit card are what you need for carbs, LOL.
Anyway to me that's part of the learning process for this crazy hobby. :)

Linda
Sadly-Linda has passed away 2022. She was the 311's den mother and drove the first Rare-Parts ball joint project. RIP.
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nismou20
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Re: Carb mixture adjustment

Post by nismou20 »

The so many turns out on nozzles has never worked for me. I always pull the domes first and set the linkage even on both as well as the marginal opening at the butterfly valves with set screws. I am running RB needles and the nozzles are almost level with the bridge. Make sure the float levels are the same too. Oem N17 needles suffer at top end when idle is clean. N25 not much better but RA/RB needles work great! Just my experience.
2004 Chevy Tracker
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2005 Lotus Elise
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Linda
Fraternal Den Mother-RIP
Posts: 7807
Joined: Sat Nov 05, 2005 11:37 pm
Location: Los Angeles
Model: 1500/1600
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by Linda »

The so many turns out on nozzles has never worked for me. I always pull the domes first and set the linkage even on both as well as the marginal opening at the butterfly valves with set screws
I never considered that you could try to get a starting baseline for a idle screw/ throttle plates match with the domes off. Potentially if there was a “ magic number” for the throttle plates, as a starting point, you could reach in there and measure. As an example with a feeler guage, perhaps. I know there is a value for a degree setting for the linkeage mentioned by Z Therapy.
But as far as measuring, at least a good starting point would be nice on the plates. Then let’s say you could do the Colortune etc
Seems easier for amateurs to use starting numbers. Afterall, isn’t that what you do with a 123 dizzy, a dyno etc....numbers?

Linda
Sadly-Linda has passed away 2022. She was the 311's den mother and drove the first Rare-Parts ball joint project. RIP.
coopccooper
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Joined: Tue Sep 24, 2019 8:18 pm
Location: Georgia
Model: 1500/1600
Year: High Windshield-68-70

Re: Carb mixture adjustment

Post by coopccooper »

Great write ups Team.

I was trying to use the Service Screw as an idle adjustment screw. I am only human. The previous owners' work was good aside from lack of maintenance and the idle screw adjustments.

I didn't have a fancy air suction calibration tool, so I just used the palm of my hand to feel the air draw for each carb. I started at 2.5 turns ccw from tight (all the way cw) for each screw and made minor adjustments until the suction on my palm was consistent with each carb and idle was at 600 rpm. Not bad shade tree mechanicing for a guy from Philly transplanted to GA.

Anyone else in GA have one of these?
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