Selecting power valve method Holley 4160

[Mattax]

An AFR gage isn't going to help.
AFR numbers aren't targets. They're reference points. Performance is how to determine if each change is toward or away from the goal.
Save your money and spend the time learning what each circuit does. Then you'll understand why the sequence in tuning is important and you'll not head off on the wild goose chase. Each of these changeable components has a purpose which can be tied to a specific result.

Learning to use an AFR gage is another learning curve. Going that far and a logger with rpm, and preferable also at least MAP or TPS will be more enlightning - but yes more learning.

You can save money and time by learning what the circuits do, and starting at the begining, tune one circuit at a time judging each change based on whether it improves power or efficiency.

 

[TT5.9mag]

An AFR gauge helps but is unnecessary as mattax said. Change one thing at a time and quantify the results. For primary jetting, lean it out two jet sizes at a time and go for a cruise. When it surges under cruise go back rich one jet size and go for a cruise again. If it surges go one more size rich and retest. When it stops surging in cruise, you leave the primary jetting alone.

 

[Mattax]

Here's a step by step approach.
Gages and loggers are not neccessary for most tuning.
Tune for Best Performance.
The fuel mixtures need for different loads are described in this post.
Wideband

and touched on here
Large RPM and Vacuum drop when shifting from park to gear

I'd spend the money on some chassis dyno time or drag strip time once you have the basic stuff established. The chassis dyno will have logging and they will give you a copy if they are a decent operation. That wil show power or torque vs. rpm and AFR.

Now at the drag strip, logging AFR will show if the bleeds are in the correct range for the jets being used. Also the log may show problems from excessive 'emulsion' holes so common on the newer Holley type carbs. But thats getting deep into how a carb works - and hopefully not something so far off it needs to be discussed at this point.

Good Books on Carburetor Circuits:
Urich & Fisher, Holley Carburetors and Manifolds - any edition. Used, new. The best introductory explanation and drawings of the how the basic circuits work. The rest of the book is a lot about promoting their product but useful info in there too. Especially some of the performance tuning tips.

David Vizard Holley Carburetors has more detail. I'm not sure its a better book to begin with, and because he simplifies some things, its fine to learn from, but be careful about sweeping generalizations and specific recommendations...

FREE!
Any of Chrysler's Master Technician's Conference booklets about how carburetors work.

Master Technician Service Conference - Chrysler's Training for Mechanics

The Imperial Mailing List Online Car Club is dedicated to the preservation, appreciation and restoration of Imperials and Chrysler Imperials of all years, models and body-styles.

www.web.imperialclub.info

Carburetor Fundementals 1966 and another in 1970 (with some new analogies plus updates for Clean Air Package)

also available here in pdf and bigger video

Chrysler Master Tech Service Library – Browse Model Year – MyMopar

mymopar.com

 

[Slantsix64]

Update so car is running great but when I’m looking at my vacuum gauge at Wot I have 1 inch of vacuum, then once the secondaries open I believe it hits 0 inches.

Does this mean I need my secondaries to come in a little quicker?

 

[Slantsix64]

@AJ/FormS @Mattax , the car runs great I ended up with 68/74 jets 10.5 PV, my thing now is it’s 90% but there’s a slight delay believe on the tip in when I mash the pedal, not a bog just a slow reaction to WOT for about a second or less.

I installed a 35 Nozzle when I first got the carb, the stock was a 31 Nozzle, should I try to go back stock and see if it gets better or worse?

 

[AJ/FormS]

If the hesitation occurs as you are mashing the gas from idle, then, before you do anything, increase the rpm by 100, retime the accelerator pump as may be necessary, then see what happens.
If this improves the situation, but the idle-rpm seems excessive, retard the idle timing, which is the only way to reduce the idle-rpm, once the Transfers are set..... unless you can figure out how to increase the Transfer slot fuel delivery, at a smaller throttle-opening.
IMO, tuning with a vacuum gauge is a waste of time.

Does this mean I need my secondaries to come in a little quicker?

no. it means the vacuum changed, is all.
Engines do not suck air in.
Air always moves from a high pressure area to a lower pressure area.
When you open the throttle valves, atmospheric pressure being greater than the pressure in the intake, forces air into the intake. An automotive vacuum gauge is not a vacuum gauge at all, rather, it is a pressure gauge. It measures pressure. When it is disconnected from the engine, it measures atmospheric pressure, and the guy who invented that gauge, simply calibrated that normal resting place with a big fat zero on it, but really, it is measuring about 14.7psi.
The closer to zero(14.7psi), that your gauge reads at WOT, the closer the intake is to normal atmospheric pressure.
This has zero to do with the timing of the secondaries. The dreaded bog, has everything to do with the timing of the secondaries. For a low 60foot ET, the bog has to be avoided at all costs.

 

[CRUZE 418]

No one ever mentions how mufflers can cause issues. Sure did in my case, not a 318 though, going back to my old mufflers, just don't care for the noise.

 

[Mattax]

Update so car is running great but when I’m looking at my vacuum gauge at Wot I have 1 inch of vacuum, then once the secondaries open I believe it hits 0 inches.

Does this mean I need my secondaries to come in a little quicker?

I'd say the way to test whether changing spring opening effects power favorably or not is on the drag strip. The answer on whether there is an actual advantage to a lower vacuum will depend on the intake and engine, maybe the exhaust too. A little vacuum can help the fuel mixture and distribution even though in a perfect world the lower the vacuum the higher the efficiency.

@AJ/FormS @Mattax , the car runs great I ended up with 68/74 jets 10.5 PV, my thing now is it’s 90% but there’s a slight delay believe on the tip in when I mash the pedal, not a bog just a slow reaction to WOT for about a second or less.

I installed a 35 Nozzle when I first got the carb, the stock was a 31 Nozzle, should I try to go back stock and see if it gets better or worse?

It could be the delay is too much t-slot exposure.

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It could be too much, or too little initial pump shot. So you could try 31 again and see if it helps.
It could be a little slack in contact with the pump cam, or the shape of the pump cam. Green has a sharp initial rise.

Qft carburetor help

Got an Qft ss-850 crab with mechanical secondary. The carb works great except for a slight hesitation off the line. Change the squirter size up 2 size but still have the issue. When I move the throttle the pump arm moves instantly and I get a shot of fuel right away. I'm running a pink...

www.forabodiesonly.com