Vacuum gauge adjusting mixture
 

I am trying to hook up my vacuum gauge to my Rochester quadrajet so that I can adjust my mixture screws. What is the best port to connect it to. Also how do I find out my carburetor number just in case I need to order parts for it?

Re: Vacuum gauge adjusting mixture
 

Your Id number will be here.
Attachment 2054347









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Re: Vacuum gauge adjusting mixture
 

To adjust carb with vacuum gauge use a full manifold vacuum port
circled below.
Attachment 2054351









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Re: Vacuum gauge adjusting mixture
 

To adjust the idle mixture.
With the engine fully warmed up, and if possible,
the air filter on.
Connect a tune-up style tachometer so an accurate engine speed can be seen .
I like the tach better than the vacuum gauge but one or the other would be ok.(Or Both)

(I normally just adjust by the sound of highest RPM now-days)

With the engine off, gently seat both mixture screws and then turn each one out (rich) two revolutions. Turn each mixture screw in (lean) slowly in 1/8th of a revolution increments until the engine speed starts to drop. Allow time for the engine to respond. Then, in 1/16th increments, slowly turn the mixture screw out until the highest rpm is reached. Repeat the procedure for the other side. Idle speed adjustment may be required after adjusting the mixture screws.

Hope this helps.







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Re: Vacuum gauge adjusting mixture
 

I have an automatic transmission. Should I have it in park while doing this?
Thanks for the help

Re: Vacuum gauge adjusting mixture
 

Two sources for manifold vacuum on your carb.
The blue cap or the black cap Will work.
How do you plan to adjust the mix screws?
Unmodified screws don’t use a normal flat blade screwdriver. Special tool needed.
Use a vac gauge. More accurate.

Re: Vacuum gauge adjusting mixture
 

If you post a picture of your number on the carb.
We can help you with the decipher of it also. If needed.








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Re: Vacuum gauge adjusting mixture
 

Are these the blue and black caps you are referring to?
I have a Specialty screwdriver that is just for adjusting the mixture screws. I had to buy two different ones to find one that worked. I’m getting tired of tools that don’t do what they’re supposed to do.

Re: Vacuum gauge adjusting mixture
 

Only one blue and one black there.
Use the blue one.

I made my own tool. Used it to remove the screws and cut a slot in the top for a flat screwdriver.

Re: Vacuum gauge adjusting mixture
 

Another question. I was testing to see if my accelerator pump was working so I took off my air cleaner and looked down the primary barrels and pressed down on the pump. When I did this fuel cam from the area that the yellow arrow is pointing at. But not from the squirter that the red arrow is pointing at. Is this correct?

Re: Vacuum gauge adjusting mixture
 

Yes. That’s right.

Re: Vacuum gauge adjusting mixture
 

Ok good thanks

Re: Vacuum gauge adjusting mixture
 

So I contacted a dyno tune place to see about getting my engine tuned. They said that I should bring my own metering rods because they don’t stock vary many parts for a quadrajet. Is there some sort of kit that I can get so that I will have an assortment of rods?
If it helps the number that I found on carb is Cab number is 1708050 with 2801 DNR underneath it. I was looking on a carb parts website and all the carbs they had listed had one more number.

Re: Vacuum gauge adjusting mixture
 

These guys have rods.


https://quadrajetparts.com/quadrajet...-c-128_44.html

Re: Vacuum gauge adjusting mixture
 

This is the kit that they sell. They list the selection of jets that come with it but you can customize which variety you want. Do you think that the ones they have listed are the ones I should get?

https://quadrajetparts.com/quadrajet...ept-p-301.html

Re: Vacuum gauge adjusting mixture
 

You gotta start somewhere.
Enough assortment there to make it work.

Re: Vacuum gauge adjusting mixture
 

Had a memory pop up. Might want to check this page out: https://quadrajetparts.com/rochester...parts-a-2.html

Make sure any rods you buy match the year of your carb.

Re: Vacuum gauge adjusting mixture
 

That’s interesting. I wonder how the kit works then. It says it will work for all years. Maybe because it relies more on the jets than the rods.

Re: Vacuum gauge adjusting mixture
 

That’s why they don’t supply primary rods with that kit.
By the time you buy a kit like that and some rods and get it tuned you’ll have spent close to the same amount as buying a custom tuned to your motor rebuilt carb.

I’d bet your dyno tune guy doesn’t Know enough about quadrajets to tune it right.
I’d test him!
Ask a simple question.
Give him no info. Nothing at all. Don’t mention this forum. Absolutely nothing.
Ask him how do you adjust
the APT.
I’d bet he won’t know.

Re: Vacuum gauge adjusting mixture
 

I got the same impression when they said they don't have a lot of the parts but I know that this is a vary good dyno shop. It is where they film engine masters. It might just be that they don't work on quodrajets as much as other carbs so they are not as well stocked.

Re: Vacuum gauge adjusting mixture
 

Not well stocked don’t matter if they’re not knowledgeable.
I think you’re wasting your money.

Re: Vacuum gauge adjusting mixture
 

So I contacted them to ask what size metering rods I should bring and they said a spreads of 5 numbers from what you have now so if you have like a 6547 go like 6042 in metering rods.up and down from what you already have.

So I guess my question is does anyone have any idea of what size metering rod my carb would have come with.

Re: Vacuum gauge adjusting mixture
 

Take a pic of the carb number.
One we can see clearly.
I have some of that info in a motors manual.

Re: Vacuum gauge adjusting mixture
 

It’s starting to snowball!
100 bucks for calibration kit and another 100 for rods and 75 for a rebuild kit!
Plus dyno guys. Maybe another 200.
Could have a custom carb for 400. One that you can make adjustments to with a screwdriver.

I’ve had two of these. Paid 55 bucks for the pair. New in the box.

https://www.smicarburetor.com/produc...2/productID/18

Re: Vacuum gauge adjusting mixture
 

Sorry I was missing a number at the end because I did not look close enough at my photo.
The number is 17080507. They never asked for the calibration or a rebuild kit they only asked for the rods.