Idle too high

[grdprx]

My engine is idling too high, 1100-1200 rpm.  I have a mild built 440 with the Engle K56 cam and a new (last year) Proform 750 carb.  I was trying to fix a rich condition at idle, discovered the secondary transfer slot was completely blocked(per help from the linked thread below).  I adjusted the transfer slot to be "square" and now the engine is idling high. The rich condition is resolved though!  Seems I traded one issue for another. 
I backed off the idle adjust screw all the way, no change.  The carburetor has vacuum secondaries, I adjusted the primaries, but there isn't much change in the vacuum, I'm at 17 Hg one complete turn out.  The choke is fully open, so that's good.  I'm not that experienced with carburetors, the Proform replaces a 600 Edelbrock.  What would be my next step to address the high idle?

The thread below was a great help, but my idle issue and transfer slot being blocked seems to be a slightly different condition than what was being tracked there. 

http://www.dodgecharger.com/forum/index.php/topic,109452.0.html

[cdr]

close the secondary The link is for tuning a DP 4 corner Idle

[grdprx]

close the secondary The link is for tuning a DP 4 corner Idle

Ok. So the transfer slot on the secondary is supposed to be blocked off with vacuum controlled secondaries?  I guess that would put me back to battling the rich idle condition.  Would that be adjusted with changing jets?

[XH29N0G]

I think something else is causing the idle to be too high and the mixture too rich.  I'll preface what I say with the statement that cdr knows more than me, but I'll see if I can figure something out.  I have not seen an idle that high and a rich condition. 

Some questions:
What evidence leads you to diagnose a rich condition?
Will the idle drop if the secondaries cover the tranfsfer slots completely?
Have you set the initial timing to the optimum and are you tuning the idle with a vacuum gauge. 

I generally set the idle at something like 800 RPM (It doesn't sound like you can get there) and then work with the vacuum gauge and timing to optimize.  I have changed the IFR and other things in my carburetor, but I am not sure you are at that stage. It isn't super difficult. 

[cdr]

How do you know its rich ?

[grdprx]

How do you know its rich ?

Black smoke upon startup and a very gassy smell walking behind the car.  Spark plugs were pretty black as well. 
I'll get a picture of those shortly, they have been replaced.

[cdr]

How do you know its rich ?

Black smoke upon startup and a very gassy smell walking behind the car.  Spark plugs were pretty black as well. 
I'll get a picture of those shortly, they have been replaced.

that sound like a possible float level,, leaking power valve ??

[grdprx]

I think something else is causing the idle to be too high and the mixture too rich.  I'll preface what I say with the statement that cdr knows more than me, but I'll see if I can figure something out.  I have not seen an idle that high and a rich condition. 

Some questions:
What evidence leads you to diagnose a rich condition?
Will the idle drop if the secondaries cover the tranfsfer slots completely?
Have you set the initial timing to the optimum and are you tuning the idle with a vacuum gauge. 

I generally set the idle at something like 800 RPM (It doesn't sound like you can get there) and then work with the vacuum gauge and timing to optimize.  I have changed the IFR and other things in my carburetor, but I am not sure you are at that stage. It isn't super difficult. 

Yes, the idle is in a normal range with the transfer slot blocked, which is how I received it as new.
The timing is set as best I recall to sort out a pinging issue.  The car runs good.  And I do have a vacuum gage to setting the idle screws on the carb.

[grdprx]

How do you know its rich ?

Black smoke upon startup and a very gassy smell walking behind the car.  Spark plugs were pretty black as well. 
I'll get a picture of those shortly, they have been replaced.

that sound like a possible float level,, leaking power valve ??

I could look into that.  It was a brand new purchase from Proform, but I can check.  What evidence of a leaking power valve should I look for?

[XH29N0G]

I would start with the idle mixture screws and tune as I'm sure you know for max vacuum at a given idle speed.  Typically I back off (richen) about 1/8 turn from that setting because otherwise it wants to stall.

Then I would note how many turns they are backed out.  If they are not backed out the typical amount (I think 1- 1.5 turns), then you may want to look into other changes.  I found it to be a learning curve, but I also found it was possible to dial in what the carburetor as I learned.

Idling can make the plugs black, especially cold idling.  The eye burning exhaust is a symptom of rich. 

From my limited experience, the initial timing at idle can also make a big difference in the mixture and how it runs.  That is why I asked before.  The catch is that the top end timing also needs to not be too high, so both have to be worked on.  What is your initial timing?  Maybe someone who knows your cam can give a recommendation on what is a good setting for it.

You say 17 inches of vacuum, is that at 1100?  I don't know the engle cam and what that should pull at a reasonable RPM.  But someone else may know.

I would look at the idle circuit.  How many turns are the idle mixture screws backed out

Just some thoughts. 

[grdprx]

Thank you, I will check on those in the morning.

[Bronzedodge]

I could look into that.  It was a brand new purchase from Proform, but I can check.  What evidence of a leaking power valve should I look for?

I believe if you close the idle screws and it still idles, that's usually a blown power valve.

[XH29N0G]

Interesting. I saw the powervalve comment and started wondering about the path the gas would take.  Here are some pictures of the metering block, body and throttle body that appear to show a passage that makes it to the bottom of the carb on one side (primary, but I don't see it going through on the secondary side.

Is this how the gas gets sucked in if the power valve is blown, or does it leak some other way.  I assume the idle circuit is pretty separated from the power valve circuit.

[grdprx]

I could look into that.  It was a brand new purchase from Proform, but I can check.  What evidence of a leaking power valve should I look for?

I believe if you close the idle screws and it still idles, that's usually a blown power valve.

Correct, that is the same info I found on a Holley forum.
" If you still suspect the power valve is blown out, start your engine and allow it to idle and get to normal operating temperature. Then, turn the idle mixture screws all the way in. If the engine dies the power valve is not blown."

My engine died, so I appear to have a good power valve.  I returned the secondary adjustment screw back to its original setting, idle is at 900-950 rpm.  Set screws are one turn out for 14 Hg vacuum, that the max vacuum at idle.

[XH29N0G]

That doesn't sound like things are that far out of wack.  Mine is set up so it is 1.25 out.  Do you have any way to measure the air fuel ratio?  I have a meter and my experience really has been that it depends on timing as to where it tunes up best.  In my case, more advanced initial (about 18) allowed the engine to run more smoothly and also a leaner idle.  I had to change the mechanism in the distributor to give it a total that was not too high though, and I don't have a vacuum advance.  I am guessing the vacuum advance would help things which brings me to a question about whether the vacuum advance is working The ignition can have an effect on how one has to tune the carburetor.  So also make sure you check all the electrical out.  Does the car stall if you make it more lean than the maximum vacuum?  Or if you leave it at that? 

[grdprx]

I don't have the ability to check the A/F ratio.  I'd also have to go "rent a tool" to check the timing, I don't recall what it's set to initially.  I did have a struggle battling a pinging issue at WOT with the car a few years back, there was a very fine window to not have it ping.  I'll report back when I get a timing light I it.  Thank you!

[XH29N0G]

IF SOMEONE ELSE, ESPECIALLY CDR, c00nhunter, bsb67, challenger340 etc... SUGGESTS SOMETHING DIFFERENT THAN ME - LISTEN TO THEM BECAUSE THEY KNOW MORE THAN I DO).  

Since you don't have a timing light, it is worth checking all other possibilities first.  

• You did the power valve check.  
  
• I would check everything with the ignition first.  I am assuming you have converted to electronic, but if you are running an old point style ignition, there are other things worth checking.
  
• With the ignition sorted, my order of checking would be  float level, but I am thinking this will then require the idle mixture screws to reset and you will be close to where you started.
  
• I might also check to see if the car ran OK with the idle mixture screws set  at (or even 1/8 or 1/4 turn in (lean)) from where you measure the optimal vacuum.  My guess this will cause the car to misbehave by wanting to stall or even backfiring through the carburetor, especially when cold.
  

But my suspicion is related to timing and that you are using an aftermarket cam (which may need more initial timing). Then backing off the total timing so it will not ping resulted in lower initial advance when the cam you have wanted more advanced initial timing.  If this is the case, you will need to change the timing setting and the range of the mechanical advance so that you have the initial and total set at the level that idles best and also does not cause detonation.  If I were doing this, I would:

• I would record the timing at idle and at full mechanical advance (I assume something like 3500 RPM but it is the RPM where the timing stops increasing).  This is done without vacuum advance connected.  I would keep this information in case I needed to return it to that value. This would also give me an idea of what total mechanical advance was in the car.  I always have to remind myself that detonation can be timing, but it can also be other things and it could be that you reduced the total timing to fix the ping and that reset the idle timing so it was low and needed to be rich to run.
  
• I would check to see if idle speed increases or quality increases with a few degrees advance in initial timing.  This usually requires resetting idle mixture and RPM. You can advance too far and then it won't want to start, but I think that is when it is in the 20 - 30 degree range.  I found the optimum setting for my set up (18 degrees) by advancing timing bit by bit until no clear increase was found.  
  
• Since I changed the initial advance and this then would change tot total mechanical advance, I then needed to change the total mechanical advance and how it comes in as RPM rises.  My distributor is one from MSD and uses different bushings to set the total advance and springs to set how it comes in as RPM rises which can be bought in a kit.  It wasn't super difficult to do and I managed to get a better idle, better idle mixture, and eliminate detonation. This is the goal and I am sure you will get there.  I hope fixing these things is also something you like.  For me, it is one of my happy places.
  

I wouldn't worry about trying to read A/F; that question was just a question out of curiosity.  The gauges can be fun and helpful for tuning carburetor in various RPM ranges and under various driving condition, but are not essential and for me, created more trouble in some cases than it solved.

Also, while it is possible to adjust the timing forward slightly (without a timing light) to see if the idle increases and work from there by feel, I think in the end you will be happy to know both the total and the initial readings and then work from there.

[grdprx]

Went through a few things today:
1.  Yes, I tested the power valve, turning the idle adjustment screws all the way in.  The engine died as it should have if the power valve was good, per info I found on a Holley fourm.
2.  I was able to turn the idle screws in a quarter turn without any negative effect, ran the same at 3/4 turns out.
3.  Got a timing light, it read at 0*...  So I advanced the timing forward until it ran rough, then set it back a few degrees.  Initial is set at 16* and at 3000 rpm it's 26-28* as best I can estimate.  I'm running a Firecore distributor that I installed a few years back.  Took the car out for a spin, and the ping is back above 2,500 rpm.  It seems your suspicion was correct, I had lowered the initial advance to no cause the detonation.  In all my troubleshooting before, I never found any other solution besides backing the timing off.

[c00nhunterjoe]

From the 1st post- turning the idle screw full kut has no effect on idle speed 1 of 2 things. Massive vacuum leak, or mechanical binding in linkage on the carb or throttle cable. Fix that 1st.
   2nd- 16 inital and 26 total should not ping at all. Something is wrong with either the balancer or light or a major internal mechanical cam timing. Or you have a 13:1 engine running 87 octane.

[grdprx]

From the 1st post- turning the idle screw full kut has no effect on idle speed 1 of 2 things. Massive vacuum leak, or mechanical binding in linkage on the carb or throttle cable. Fix that 1st.
   2nd- 16 inital and 26 total should not ping at all. Something is wrong with either the balancer or light or a major internal mechanical cam timing. Or you have a 13:1 engine running 87 octane.

I wasn't clear about that, I meant the idle adjust screw on the primary linkage, where the throttle cable attaches.  I'm beginning to think my timing marks aren't accurate. It's a low budget 8.5:1 engine, nothing special.
Backing the timing off to where it doesn't ping, and the car has good power.

[c00nhunterjoe]

From the 1st post- turning the idle screw full kut has no effect on idle speed 1 of 2 things. Massive vacuum leak, or mechanical binding in linkage on the carb or throttle cable. Fix that 1st.
   2nd- 16 inital and 26 total should not ping at all. Something is wrong with either the balancer or light or a major internal mechanical cam timing. Or you have a 13:1 engine running 87 octane.

I wasn't clear about that, I meant the idle adjust screw on the primary linkage, where the throttle cable attaches.  I'm beginning to think my timing marks aren't accurate. It's a low budget 8.5:1 engine, nothing special.
Backing the timing off to where it doesn't ping, and the car has good power.

Right. If you turn the idle screw where the throttle cable attaches and the idle doesnt lower- thats something binding or broken, not a timing or mixture adjustment. Make sure the cable isnt too short and keeping it from closing.

[RallyeMike]

Make sure the cable isnt too short and keeping it from closing.

Good call to check this. Look to see if there is a gap between the idle screw and its stop. Is your return spring strong enough to firmly pull the cable back every time? I prefer to adjust my throttle cable so it is just a hair loose and long as I can still assure that I can attain WOT.

[DanielRobert]

First thoughts; the choke idle screw is too far in and the second , disconnect the throttle cable and see if it idles lower.

[grdprx]

Sorry for my delay in getting back to reply.  Apparently I'm an essential worker, so I had to deal with that change a few weeks back after being off for 4 weeks.  My throttle cable has slack in it while at idle, so that isn't the culprit.  Based on the input from CDR and c00nhunterjoe, I've gone back to square one.  Here is where I sit:

-Proform 750 DP vacuum secondary carburetor was returned to stock setting
-new spark plugs were installed
-Idle is normal at 950 rpm, but with a rich fuel smell.
-Black smoke is emitted from the tailpipes upon initial start up
-timing was returned to settings prior to this troubleshooting (seems timing isn't accurately being read)

I'll have to find some time this weekend or Memorial weekend to work on it again.