Holley 4160 tuning help

Hack · Sep 20, 2007

I have a 600 cfm Holley 4160 PN 0-80457 on my 302 in my 70. It's a 302 from a 89 Mustang GT with a Weiand Stealth intake, Fox factory shorties and 2.5" dual exhaust.

I have a couple problems with the carb, but I no longer trust the advice in my Haynes Holley Carb Manual after trying to use it for the basic set up and getting the car running. Uggh, sorry for the long post.

The car is running very rich. I get black soot out of the tailpipes on startup, so I assume that is the problem. I think I need to jet the carb down. Any advice on what jet(s) I should buy/start with?

Also, the choke makes the rpms race too high and I think it takes a little too long for the choke to come off.

What order should I tackle these problems? Is one adjustment likely to affect the other?

ratio411 · Sep 20, 2007

There is a seperate idle adjustment screw for the choke.
The main one only controls idle when the choke is off.
The idle for the choke is called "fast idle screw" and is located on the side behind the choke linkage. That will keep it from racing.

Don't bother with jets yet.
The jets only control the mixture when the main circuit is 'on'.
This is when you are driving steady.
Acceleration brings the power valve and accel pump circuit into play as well.
The idle circuit only deals with the idle mixture screws and the 2 idle speed screws. It can involve the power valve if it is ruptured. Then it will load up constantly at idle.

If you have an electric choke, you can lean it out and get the choke to pull off sooner by adjusting the housing.
Loosen the screws and turn the housing lid until the choke pulls off a little.
There is a spring in there that can be tightened/loosened by turning the lid.
The tightness of the spring in turn governs how long your choke is on.
This can and will affect mixture when the engine is cold.

Hope this helps.
Dave

Edit:
Forgot the other question: "will one affect the other?"

Yes.
Adjust your choke first.
Get it pulling off sooner.
Then adjust your fast idle.
Then adjust your idle speed and idle mixture, they affect each other and are done at the same time.
Now make sure the accel pump linkage wasn't thrown out of whack.

If all is well, great.
Then you can fine tune the jets if need be.
If you still can't get the problem gone, replace the power valve.
If you just can't seem to get any adjustment to keep it from loading up, it's usually the power valve.
The other would be a float level set too high and fuel spilling over into the venturis at idle. Too much fuel pump pressure could cause this issue too. A piece of junk sticking a needle open slightly is an off possibility...

D.Hearne · Sep 20, 2007

If you're not going to drive it in the winter, I'd say ditch the choke mechanism all together. Check the float/fuel level in the bowls. Jets would be the last thing that would be off, unless someone else changed them. Did you or someone else rebuild the carb?

StangDreamin' · Sep 21, 2007

Subscribing - cause it's been a while since I had to tune a Holley 4160

Hack · Sep 21, 2007

D.Hearne said:
If you're not going to drive it in the winter, I'd say ditch the choke mechanism all together. Check the float/fuel level in the bowls. Jets would be the last thing that would be off, unless someone else changed them. Did you or someone else rebuild the carb?

Thanks for posting, D.Hearne.

I see what you and ratio411 are saying. It's probably the idle and choke that need adjustment. I have checked the fuel levels and the back bowl just a little fuel dribbles out and the front bowl no fuel comes out.

The carb hasn't been rebuilt.

Can you explain the best way to adjust the idle?

I'm only going to drive the car between about 40-100 degrees temperature range (summer in Minnesota). Do I need a choke?

D.Hearne · Sep 21, 2007

First thing I do when I get a Holley is completely remove all traces of any choke mechanism, my weather's a bit better than yours, but even on 20-30 degree mornings, all I have to do is baby it a few minutes till it idles on it's own. To set the idle, I first set the initial timing,(I nearly always set this to 12* BTDC) then set the idle speed (the large screw that adjusts the throttle blade opening) then fine tune the idle with the mixture screws. If you have no fuel dribbling out the primary side, raise the float, counter clockwise raises it (big nut topped by the large screw on the bowl top)

Hack · Sep 21, 2007

What's the best way to fine tune the mix screws? They don't seem to do a lot for me. I followed the directions in my carb manual, but adjustments didn't seem to have the effect that the manual said they should. I ended up screwing them all the way in and then backing them out 1 1/4 turns, because nothing seemed to improve it or cause the idle to change the way the manual said it should.

I could swear I've heard something about using a vacuum reading to set the mix. Is that how you do it? Maximum vacuum?

danny clemens · Sep 21, 2007

Hack said:
I could swear I've heard something about using a vacuum reading to set the mix. Is that how you do it? Maximum vacuum?

That's the way I do it.

ratio411 · Sep 21, 2007

I never get good response from the idle screws either...
I screw them in all the way, then out 1.5 turns.
Unless my eyes water at idle , I leave them there.

I know you are supposed to get the highest idle you can with the screws, then adjust your curb idle to base setting. Then it is supposed to be best lean idle.
I never get a clear response. But then again, I am going totally by ear, which aren't so good nowadays.
A tach and vacuum gauge would surely be the way to go.

ratio411 · Sep 21, 2007

Oh, was also going to post that I never have used a choke either.
If the carb isn't leaking, and the weather isn't freezing, you don't really need one.

D.Hearne · Sep 21, 2007

I get some response from the mixture screws, but if you're getting no response, there's a chance you have the idle speed screw opening the throttle blades far enough to uncover the transfer slot in the base plate. Once that's uncovered, the mixture screws do nothing, the carb is then in "transition" and off the idle circuit. If this is the case, something's not kosher, if you have to use that much adjustment to get the idle speed set.

Hack · Sep 22, 2007

danny clemens said:
That's the way I do it.

Ok, but how? Which screw first, which second, or do you just keep going back and forth?

danny clemens · Sep 23, 2007

You can adjust either one first. After adjusting both you could go back to the one that you did first to see if that makes any difference. That's the way I used to do my old Autolites. Up until recently I've never owned a 4160 (bought a new 750 cfm one about 2 weeks ago but it's still in the box) and really don't know the characteristics of one. You'd probably be better off listening to the guys that have had hands on experience with a 4160 since different carbs have different characteristics.

D.Hearne · Sep 23, 2007

The Autolite 2100/4100 are pretty similar to a Holley 2300/4150/4160, so you should be a step ahead of where you think you are. Holley even made a 4 bbl carb that's almost a dead ringer for the 4100, this carb is the Holley 4010. Parts that are similar with all are the powervalve, jets, accellerator pump diaphram, idle mixture screws, plus more I can't think of off hand.

pabear89 · Sep 23, 2007

Hack said:
Ok, but how? Which screw first, which second, or do you just keep going back and forth?

You need to start with a base adjustment first.
making sure the fast idle cam is disengaged, turn the idle speed screw all the way out so it is not touching the throttle stop.
Now turn it in till it just touches the stop plate and add 1 1/2 turns in.
Bottom the idle mixture screws (Lightly so not to score them) and turn them both out 1 1/2 turns.

Check the choke settings, move throttle linkage to set choke.
look to see where the fast idle screw is resting on the fast idle cam behind the choke coil housing and how much it has opened the throttle blades.
adjust the fast idle screw to open or close the throttle plates to correct rpm setting. 1200 works well.

Start eng and check float settings, should just barely seep fuel out the hole whiile running.
Bring eng to operating temp and check that choke has opened and released fast idle cam.
adjust idle speed screw to 700 rpm.
Now your idle mixture screws should make noticable changes when moved in or out.

Now I use an old trick to balance both sides of the mixture.
I move the choke plate to allow the fast idle cam to raise the idle to approx 1000 rpm. then tweek the mixture screws to give the smoothest idle by turning each slightly and listening for changes. a little will turn will do a lot.

Now you can adjust the axcell pump. I start with the pump screw gapped at .005 clearence to the pump. and adjust tighter or looser to time the squirt so there is no flatspot or bog when you hit the throttle.

PB

Internexus · Sep 23, 2007

There is a lot of good information for setting up a carb in here. I have always been anti carb and die hard for fuel injection, however I am moving on towards my 65 stang again and it's obviously a good move to start understanding what that creature is on top of the motor. Are there any worthwhile books to invest in guys?

D.Hearne · Sep 24, 2007

Haynes Holley carb manual. It will tell you a lot, including the basics.

Internexus · Sep 24, 2007

I've always been rather anti haynes/chiltons manuals as they were never really descriptive enough to specific things in my opinion. You actually feel this is a good book though? Is it just a general carb book or specifically over Holley's, or model specific Holley's?

D.Hearne · Sep 24, 2007

It's a Holley only book. It's good enough for me.

Hack · Sep 25, 2007

I've had some trouble with the Haynes Holley carb book, and reading comprehension is typically my strongest suit. However I won't argue that there is a TON of great info in there. Lots of pictures and diagrams of many different carb models.

Holley 4160 tuning help

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