Rich Idle help...yes I know...Update

[CUDA JAS]

 My cuda is idle very rich...it makes the car almost unpleasent to drive...please help me tune out the richness.

My sepecs:

74 Cuda with a 360,
Eddy Performer RPM intake,
Eddy torker Plus cam,
The specs are as follows:
@050 Int dur. 222 , Ex dur. 234
Lift Int .447 Ex .450
Intake Centre line 107 Ex centerline 116.
About 9:1 compression.
Holley 750 vac secondary carb.
Dizzy has been recurved, running 18 initial, 38 total all in before 3000.
Vac advance hooked up to manifold vac (as per Don at FBO), 44 deg advance at idle. (maybe too much)
727 with stock converter
8-3/4 with 3.22s

I have tuned the carb to get maximum vac at idle 12, in drive, nice idle at 800rpm.

When I turn in the mixture screws, the engine will stumble and want to stall out.

The float level looks good, right under the sight holes.

When I look down the carb when its idleing away, there is no gas comming out the boster, ventruis are nice and dry.

Power valve is the stock 6.5.

Mixture screws are about 1 turn out.  Turn themin any more and the vac and idle quality suffer.

The car runs good, nice and strong off idle, no hesitation.

But it idles away VERY RICH!!!   :realmad:

The only thing I have not done, is pull the mixture srcews out and clean the passages ( :shruggy: ), or pull the carb apart and really clean it (bought new 3 years ago).

Any thoughts tips tricks woudl be appreciated.

Thanks,

Jason

[Cuda54]

Is the choke wide open at idle? We had that problem on a different motor and carb. But the secondary was not closing far enough there is a screw to adjust it. You will need to remove the carb to get to it. To much vac can open the secondary too. Try to back off on the vac to see if it helps.

[Chryco Psycho]

- First I would disconnect the vacuum advance entirely try driving it this way , it should both run better & cooler .
- Second what is your vacuum at idle in gear , if it si near 7" you need a lower power valve , a 4.5 " would not hurt.
- Third pull off the carb & see if the light arond the throttle plates is about even , if the front is open more ther is a small set screw to open the rear up a little more , then you shopuld be able to close the primary down a bit a balance the opening a bit better .
 - Fourth you may need to enlarge the metering for the Idle circuit , I don't know what model carb you have but you may need to drill the brass insert or better yet unthread it & replace it with a slightly larger one , this requires numbered drill bits , you only need to open it a couple of thousands of an inch . When you look down the top of the carb you will see 4 brass inserts in both the front wall of the front venturis & the back wall of the rear , the outer ones control the idle circuit
Start there . I hope this helps , Neil

[CUDA JAS]

Is the choke wide open at idle? We had that problem on a different motor and carb. But the secondary was not closing far enough there is a screw to adjust it. You will need to remove the carb to get to it. To much vac can open the secondary too. Try to back off on the vac to see if it helps.

Yep...manual choke...full open.

I currently have the stongest spring in the vac secondary spring.  I have also adjusted the secondary stop and increased the opening.  (i came up with away to do this on the car btw).

[CUDA JAS]

- First I would disconnect the vacuum advance entirely try driving it this way , it should both run better & cooler .
- Second what is your vacuum at idle in gear , if it si near 7" you need a lower power valve , a 4.5 " would not hurt.
- Third pull off the carb & see if the light arond the throttle plates is about even , if the front is open more ther is a small set screw to open the rear up a little more , then you shopuld be able to close the primary down a bit a balance the opening a bit better .
 - Fourth you may need to enlarge the metering for the Idle circuit , I don't know what model carb you have but you may need to drill the brass insert or better yet unthread it & replace it with a slightly larger one , this requires numbered drill bits , you only need to open it a couple of thousands of an inch . When you look down the top of the carb you will see 4 brass inserts in both the front wall of the front venturis & the back wall of the rear , the outer ones control the idle circuit
Start there . I hope this helps , Neil

Neil,

I will try disconnecting the vac adv.  I was lead to believe that more advace at idle would provide a cleaner idle, but I will try almost anything at this point.

Idle in D is 12.  I was thinking of changing out the PV...could be bad. If I do I will go for a 5.5 or 6.

I have adjusted the scondary stop, it is open a little more then the primary.  In fact if I close the primary any more I get a wicked off idle / tip in stumble. 

I am running a 4160 holley...so the idle bleeds are not the screw in type.  Are numbered drill bits different from regular drill bits.  I presume I woudl drill them with the carb off the car and start with the smallest increase. Can this be doen acurately with a hand drill?

Thanks,

Jason

[mrob]

Jason,

I noticed you said the following: "I have adjusted the scondary stop, it is open a little more then the primary." If you opened the secondary throttle blades enough to show the transition slots, that may be the reason for the richness. It sounds like you have fuel flowing from the primary transition slots (that's normal) AND the secondary transition slots (rarely necessary). Adjust the secondary throttle blades so that they barely close against the stop (no transition slot showing) and then readjust the primary idle circuit so that around 0.040" (or less) of the transition slot shows.
Try that before resorting to playing with the idle air bleeds or the idle feed restriction.

[Chryco Psycho]

yes the bleeds can be hand drilled , # drill bits are far more accurate & very small increments , you can often buy then individually from a hobby store & just use a pin vice tool to drill with . how far are the idle screws out from bottom now ?
You can carefully solder & redrill the bleed if you need to but it is difficult
Typically you will have a 6.5 PV in there but they  do harden up & refuse to close so try that first.
You do not want the strongest spring in the secondary  , it will virtually never open making the carb a 2 bbl , this has nothing to do with the idle circuit anyway , Yellow typically works well .
I also recommend adjusting the secondary link , if you lengthen iot slightly the secondarry is forced fully closed & cannoto open until the primary is 30% open

[CUDA JAS]

yes the bleeds can be hand drilled , # drill bits are far more accurate & very small increments , you can often buy then individually from a hobby store & just use a pin vice tool to drill with . how far are the idle screws out from bottom now ?
You can carefully solder & redrill the bleed if you need to but it is difficult
Typically you will have a 6.5 PV in there but they  do harden up & refuse to close so try that first.
You do not want the strongest spring in the secondary  , it will virtually never open making the carb a 2 bbl , this has nothing to do with the idle circuit anyway , Yellow typically works well .
I also recommend adjusting the secondary link , if you lengthen iot slightly the secondarry is forced fully closed & cannoto open until the primary is 30% open

Thansk CP.

So here is my plan of attack for now. 

Reduce the amount the secondaries are open (looks liek thery are open too far),
increase the primaries to get acceptabel idle.

I will see how that runs with VAC advance hooked up.

If no better / worse, I will try it with out vac advance hooked up and see how that goes.

After that, if it is no better, I will check / replace the PV.

WRT the secondary springs, I have the heaviest in there now as I was tuning out a hesitaetion in the carb on the old intake and have not changed out the hevay spring.  I will work to a lighter spring once I have the idle issues sorted out.

Thansk,

[CUDA JAS]

Ok...a bit of an update... went for a 400 mile round trip  drive last weekend. 

I adjusted the secondaries prior to leaving, and the car ran pretty good. 

However, going down the highway (about 73 MPH at 2800 RPM), the car was runing pretty hot, aprx 220 / 225.  The car was alos running very rich (the odour from the car at speed was horrible).

SO at our first rest stop, about 45 min in, I pulled the vac advance, made no other changes, the rest of the way the car ran much cleaner, no smell, and dropped the tem to aprox 210 for the rest of the way.

I am not sure I will ever hook the vac advance back up now.

The idel is still a littel rich, but I am still workgin on it.

I think I will pull out the power valve and have a look, I have a 7.0 in my parts stash, but I think it may be to high (11.5 vac in drive).  SO I may go get a 5 or 5.5 pv to try.

Thanks for all the help guys, I will get this worked out eventually.

Jason

[Chryco Psycho]

I have no clue why people recommend hooking the vacuum to the manifold , it works opposite to what the engine wants & everytime I have seen it done the engine has run too hot

[CUDA JAS]

I have no clue why people recommend hooking the vacuum to the manifold , it works opposite to what the engine wants & everytime I have seen it done the engine has run too hot

Yep, lesson learned (which is a good thing)!

[Strawdawg]

The other thing people do is to bump up the initial timing to 16-18 degs which is a good thing-particularly if one has a longer duration cam, but, they don't reduce the amount of vacuum advance accordingly.  Vacuum advance is a good thing (on a daily driver)...but, like many good things, too much of a good thing is no longer good.

[Chryco Psycho]

you need a 20* curve ideally , total 36-38 , idle 16-18
 I have to weld the mechanical advance slots to shorten the curve

[CUDA JAS]

you need a 20* curve ideally , total 36-38 , idle 16-18
 I have to weld the mechanical advance slots to shorten the curve

CP that is just about where I am, 18 intital and I top out about 38.

As an update, i pulled the carb apart, cleaned all the passages, adn put in a 5.5 PV.

Still no change, still a rich idle  The transition slots look about right, and the secondarys are almost all the way closed.  I may open them up a bit to see if I can close the primaries a littel bit more and see if that helps.

Other than that I think I may have to drill the primarys to get a little more air in there.   

Any other ideas?!?!?!?!!?

[Chryco Psycho]

drill the throttle plates start small 1/16 " or so