Gen 3 950 dominator

[fishman]

This new Holley dominator with the idle bypass valve, I opened it up to see how it would change how the car ran. I opened the valve probably 3/4 of the way and couldn’t get car to run right. I have the bypass valve probably 1/2 way open.
Car is running fine but my 4 corner idle circuit is a big difference from drivers to passenger side
Drivers front out 1/2 turn—back 3/4 turn
Passenger out 1 1/4 turn back out 1 turn.
I’m guessing it’s not balanced . There is no guideline on how much to open up the valve.
I’m going to close up the valve more hopefully can find a balance. My camshaft is 271-280 duration @.050 750 lift installed 108. The valve comes closed from the factory but with my cam need it opened up more. Guess just have to play with it, or do any u guys have any tips. Thanks

[jmarkaudio]

The Gen 3 Dominator 950 is close, needs a couple tweaks. It has 3 open emulsion bleeds, put the open in 1 and 4, plug the other three, it requires buying blank headed 6-32 bleeds. 28 Main air bleed. And lower the idle feed, this requires buying 6-32 x 1/8 brass set screws and a tap. I suggest a bottoming tap, turn the tap 4.5 turns in the passage leading to the idle well. Start with a .040 hole in the set screw, take out the restriction at the top of the well. Details are in the following link.

https://www.tapatalk.com/groups/racingf ... t-t18.html

After you get that done set the t-slots with a square exposed, roughly .020-.030, and then use the idle bypass to set your idle speed as needed.

[fishman]

Mark sounds over my head..got to be a easier way maybe send it to you in the fall
Just thought I would try playing with the air bypass valve and close it off some for now
I forgot to mention mine is a 2 circuit carb

[NormS]

I suggest setting the idle position of the secondary butterflies( carb off engine, on the bench) so that the middle of the butterfly edges are at the bottom of the transition slots, and then leave that adjustment alone in the rest of your tuning. Then set the primary butterfly idle position so that there is .020"-.030" of the slots showing beneath the butterfly edges. Reinstall the carb, and then set the idle speed with the air bypass valve. You should do this with the engine fully warmed up, and with the trans in gear, if you have an automatic. Of course, block the tires to keep the car from moving.

Note that each time you adjust the air bypass, you may need the readjust your idle mixture screws. If you open the air bypass more, you will need the set the idle mixture screws richer to get the same idle A/F ratio as before. Try to keep all four idle mixture screws out the same number of turns, starting your adjusting process with all four out about 1 turn from fully closed.

All of these idle adjustments should be done after getting your ignition timing set where you want it, and after setting your fuel pressure and float levels with the engine running(important).

[fishman]

Norms
I secondary transition slot is probably.020 from it so have to open it up
The primary is way away from the transition slots probably double that

I’m guessing the idle is going to be way higher now . I don’t think the idle bypass will drop the rpm by that much

[NormS]

try it

[fishman]

Norms
I set the primary and secondary slots to .020
Started car up and it was reving 2200 rpm I set the primary throttle speed down, backed it all the way off and it was reving 1500 rpm , I had back off the secondary idle to get it down to 1200 rpm. I adjusted the air bleeds with the idle bypass valve closed and the drivers side is 1/2 turn out and passengers is 3/4 turn out and fumes are burning my eyes

[NormS]

The burning of your eyes is more likely to be a rich mixture. See if the engine has a stable idle with the idle mixture screws set at 1/4 turn each. If it does , I suspect you have fuel coming from some other place. The most likely place for that fuel to come from , is a leaking power valve or power valve gasket. In any event, always try to set the 4 idle mixture needles the same number of turns out.

[jmarkaudio]

Having the secondary closed more is OK, having correct primary exposure allows the transition circuit to respond correctly to small throttle openings. I've been thru a 950 already, do the things above and it runs fine.

[fishman]

Norms
I have no power valves both are plugged off
90 jets in secondary and 86 in primary. I’ve have
The gasket leak before and I find it will burn a lot of fuel if blown, I’m not using more then usual of fuel

Mark
For some reason the 4 corner idle screws on the passenger side are open 1/2 turn more then passenger side for best rpm. If I close drivers side any more car won’t run
I will try closing the secondary more? Is how much or just expierment

This carb is brand new
The motor is 422 ci sbc
AFR 235 heads
Ported super victor 4150 with a spacer to a 4500
Cam is solid roller 750 lift
106 installed 271-280 duration
Headers are custom equal length 1 3/4 tubes 3 inch collector
I’m running 38 degrees timing
Cr is 11.28
Running chevron 94 pump gas
Torque converter is 8 inch 5800 stall
Car 60 foots 1.28
And runs 9.17 147 mph
I can drop the timing back to 34 degrees so I can open primary more

[jmarkaudio]

If it is a single plane intake you should see the same response from both sides of the carb. As far as the secondary idle, just set the primary t-slot exposure and use the secondary to set idle speed. As long as they don't get overexposed, at that point you would add idle bypass air.

[MELWAY]

If it is a single plane intake you should see the same response from both sides of the carb. As far as the secondary idle, just set the primary t-slot exposure and use the secondary to set idle speed. As long as they don't get overexposed, at that point you would add idle bypass air.

Jmark
I’m this situation on a dominator do you add idle air bypass by drilling some holes in butterfly blades or is it better to add some air bleeds in top of carb main body ?

[jmarkaudio]

It should have a built in bypass thru the air cleaner stud.

[fishman]

Mark
It does what u think about bigger idle air bleeds
Has 63 right now

[BradH]

Sorry for stepping in, but it sounds to me like the OP has some misunderstandings about how & where the various circuits and tuning parameters interact.

The info in the links below looks to have been taken directly from David Vizard's latest Holley book. There's a lot more detail in the DV book itself and I suggest purchasing a copy.
https://www.cartechbooks.com/techtips/h ... rinciples/
https://www.musclecardiy.com/performanc ... ion-guide/
https://www.musclecardiy.com/performanc ... ion-guide/

I thought the following Dragzine article might be of help, too, especially if the OP has access to a wideband O2 setup.
https://www.dragzine.com/tech-stories/e ... rburetors/