Very rich idle

[Paul G]

What makes for a rich idle? Burn your eyes rich, makes your clothes stink rich, 12.1:1 A/F ratio rich. If I lean out the carb, Holley SA 670, the engine starts to stumble and doesnt like it. I adjust idle using a vacuum gauge. Adjust for the highest lean vacuum reading. Vacuum is around 16 to 18". The car idles nice and smooth, just stinks of being rich.

Any suggestions?

[BSB67]

What is your in neutral rpm?, timing, and in-gear rpm and timing?  Does it stink in both neutral and in gear? and finally, what are the cam specs.

Don't get too hung-up on idle (or WOT) A/F numbers.  Max idle vacuum signal and idle quality are the better measures.

The slightest misfire at idle will certainly stink, but that does not seem likely based on your description.  Maybe check your plugs and replace.

More initial ignition timing at idle seems to clean up the idle and smell.

Don't think that helped, but that is all I have right now.

[Paul G]

What is your in neutral rpm?, timing, and in-gear rpm and timing?  Does it stink in both neutral and in gear? and finally, what are the cam specs.

Don't get too hung-up on idle (or WOT) A/F numbers.  Max idle vacuum signal and idle quality are the better measures.

The slightest misfire at idle will certainly stink, but that does not seem likely based on your description.  Maybe check your plugs and replace.

More initial ignition timing at idle seems to clean up the idle and smell.

Don't think that helped, but that is all I have right now.

Idle RPM in neutral is 850, base timing about 30°, 34° all in at 2000, idle in gear is 750, timing starts to advance at 1000 rpm.
Yes, stinks in neutral and in gear. Cam is an unknown? I am starting to believe the cam may be degreed in advanced based on the timing that it likes, and all the low end torque it makes compared to the HP. At the wheels it makes 255 hp, 360 TQ.

Idle vacuum is pretty good at 16".   

[BSB67]

What is your in neutral rpm?, timing, and in-gear rpm and timing?  Does it stink in both neutral and in gear? and finally, what are the cam specs.

Don't get too hung-up on idle (or WOT) A/F numbers.  Max idle vacuum signal and idle quality are the better measures.

The slightest misfire at idle will certainly stink, but that does not seem likely based on your description.  Maybe check your plugs and replace.

More initial ignition timing at idle seems to clean up the idle and smell.

Don't think that helped, but that is all I have right now.

Idle RPM in neutral is 850, base timing about 30°, 34° all in at 2000, idle in gear is 750, timing starts to advance at 1000 rpm.
Yes, stinks in neutral and in gear. Cam is an unknown? I am starting to believe the cam may be degreed in advanced based on the timing that it likes, and all the low end torque it makes compared to the HP. At the wheels it makes 255 hp, 360 TQ.

Idle vacuum is pretty good at 16".   

Make sure I understand. Initial timing is 30°, full advance is 34° in at 2000 rpm.

I would check, if you haven't, to make sure that the timing is not moving in between neutral and in-gear engine speed.  I.e. check in-gear timing.  Although this is not going to fix stink.

I wonder if that much initial timing is too much for your motor.  I doubt that that would effect stink, but I would try less initial, just too see.

Does the 670 have four corner idle? If you think you have the mixture screws as good as they are going to get, I would maybe try larger idle air bleeder restrictors.

[RollinThunder]

My guess is it is lean at idle, or the boosters are dripping fuel at idle.  How many turns out from fully seated are the idle mixture screws?  If you continue to turn the idle mixture screws out will the mixture go rich enough to cause a drop in idle rpm?
If the primary boosters are dripping fuel at idle then you need to fix that.  I would think with 30 degrees initial timing, and the vacuum, that this is not the problem.  However 850 idle rpm is a tad high.
If the mixture screws won't richen the mixture enough to cause an idle rpm drop, then I would open up the TQ's IFR's about .003 inch.  If they are currently 0.034" then enlarge to 0.037".  TQ's were emission era carburetors and were lean with the stock stuff.  Using today's fuel, and different cams, intks, etc... only makes it worse.

[Paul G]

Make sure I understand. Initial timing is 30°, full advance is 34° in at 2000 rpm.

I would check, if you haven't, to make sure that the timing is not moving in between neutral and in-gear engine speed.  I.e. check in-gear timing.  Although this is not going to fix stink.

I wonder if that much initial timing is too much for your motor.  I doubt that that would effect stink, but I would try less initial, just too see.

Does the 670 have four corner idle? If you think you have the mixture screws as good as they are going to get, I would maybe try larger idle air bleeder restrictors.

Idle and in gear, timing stays the same. I cleaned off all the old sharpie marks that were on the damper and remarked it in 10° BTDC increments. Base timing is about 25°, total about 35°, and yes all in by 2000 RPM.

In an effort to cure an off idle stumble I richened the carb's initional shot 10 ways from Sunday, to no avail. Put all that back to stock and tried increasing base timing, that cured the off idle stumble. I kept giving it more timing waiting for the engine to labor. It almost never did. It does not buck the starter hot or cold, I arrived at the 25° base timing by pulling out the dizzy, closing the window in the Mopar Performance dizzy a little, Set the total timing back to 35°, and the base just fell in at about 25°. Thats where I left it.

No 4 corner idle on the 670. Air bleed restrictors? I will have to do a little research and see if they are adjustable on the SA670?

My guess is it is lean at idle, or the boosters are dripping fuel at idle.  How many turns out from fully seated are the idle mixture screws?  If you continue to turn the idle mixture screws out will the mixture go rich enough to cause a drop in idle rpm?
If the primary boosters are dripping fuel at idle then you need to fix that.  I would think with 30 degrees initial timing, and the vacuum, that this is not the problem.  However 850 idle rpm is a tad high.
If the mixture screws won't richen the mixture enough to cause an idle rpm drop, then I would open up the TQ's IFR's about .003 inch.  If they are currently 0.034" then enlarge to 0.037".  TQ's were emission era carburetors and were lean with the stock stuff.  Using today's fuel, and different cams, intks, etc... only makes it worse.

Idle mix screws are a about 1 1/2 turns out give or take. Coming out more will make the idle get rough and start to drop, noticably rough with another 1/2 turn out. I adjust the mixture screws till the vacuum stops rising, the needle on the gauge smooths out right at that point. Any richer and the needle starts to drop. I have not seen any dribbling from the boosters.   

After the trip to Vegas I will rig a piston stop and verify TDC. I have tried to move the outer ring on the damper with my giant screw driver. It is solid, no flex. But it still could be off I guess.

On a side note, The engine is starting to burn oil. I saw it on the chassis dyno videos from a couple of weeks ago at the HEMI show. Lots of blue smoke out the tail pipes on deceleration. It did it after each pull. Also when just idling in the garage for an extended period. like when messing with the carb, it will start to smoke out the tail pipes. Valve guides seals maybe? 

[BSB67]

Make sure I understand. Initial timing is 30°, full advance is 34° in at 2000 rpm.

I would check, if you haven't, to make sure that the timing is not moving in between neutral and in-gear engine speed.  I.e. check in-gear timing.  Although this is not going to fix stink.

I wonder if that much initial timing is too much for your motor.  I doubt that that would effect stink, but I would try less initial, just too see.

Does the 670 have four corner idle? If you think you have the mixture screws as good as they are going to get, I would maybe try larger idle air bleeder restrictors.

Idle and in gear, timing stays the same. I cleaned off all the old sharpie marks that were on the damper and remarked it in 10° BTDC increments. Base timing is about 25°, total about 35°, and yes all in by 2000 RPM.

In an effort to cure an off idle stumble I richened the carb's initional shot 10 ways from Sunday, to no avail. Put all that back to stock and tried increasing base timing, that cured the off idle stumble. I kept giving it more timing waiting for the engine to labor. It almost never did. It does not buck the starter hot or cold, I arrived at the 25° base timing by pulling out the dizzy, closing the window in the Mopar Performance dizzy a little, Set the total timing back to 35°, and the base just fell in at about 25°. Thats where I left it.

No 4 corner idle on the 670. Air bleed restrictors? I will have to do a little research and see if they are adjustable on the SA670?

My guess is it is lean at idle, or the boosters are dripping fuel at idle.  How many turns out from fully seated are the idle mixture screws?  If you continue to turn the idle mixture screws out will the mixture go rich enough to cause a drop in idle rpm?
If the primary boosters are dripping fuel at idle then you need to fix that.  I would think with 30 degrees initial timing, and the vacuum, that this is not the problem.  However 850 idle rpm is a tad high.
If the mixture screws won't richen the mixture enough to cause an idle rpm drop, then I would open up the TQ's IFR's about .003 inch.  If they are currently 0.034" then enlarge to 0.037".  TQ's were emission era carburetors and were lean with the stock stuff.  Using today's fuel, and different cams, intks, etc... only makes it worse.

Idle mix screws are a about 1 1/2 turns out give or take. Coming out more will make the idle get rough and start to drop, noticably rough with another 1/2 turn out. I adjust the mixture screws till the vacuum stops rising, the needle on the gauge smooths out right at that point. Any richer and the needle starts to drop. I have not seen any dribbling from the boosters.   

After the trip to Vegas I will rig a piston stop and verify TDC. I have tried to move the outer ring on the damper with my giant screw driver. It is solid, no flex. But it still could be off I guess.

On a side note, The engine is starting to burn oil. I saw it on the chassis dyno videos from a couple of weeks ago at the HEMI show. Lots of blue smoke out the tail pipes on deceleration. It did it after each pull. Also when just idling in the garage for an extended period. like when messing with the carb, it will start to smoke out the tail pipes. Valve guides seals maybe? 

I noticed the smoke as well.  Could be the seals, and that is the simplest thing to look at and do.  Usually the guides are worn as well.

The off idle stumble might be fixed with opening up the idle feed restriction, verses putting in a bunch of timing. The near instant, light throttle, off idle hesitation is often times due to lean idle and transition, not the squirter, if that is what yours was doing.  The last SA I worked on had this same stumble.  It would also show up if you blip the throttle in neutral.  99% of people you ask will say squirter. 

[c00nhunterjoe]

Make sure I understand. Initial timing is 30°, full advance is 34° in at 2000 rpm.

I would check, if you haven't, to make sure that the timing is not moving in between neutral and in-gear engine speed.  I.e. check in-gear timing.  Although this is not going to fix stink.

I wonder if that much initial timing is too much for your motor.  I doubt that that would effect stink, but I would try less initial, just too see.

Does the 670 have four corner idle? If you think you have the mixture screws as good as they are going to get, I would maybe try larger idle air bleeder restrictors.

Idle and in gear, timing stays the same. I cleaned off all the old sharpie marks that were on the damper and remarked it in 10° BTDC increments. Base timing is about 25°, total about 35°, and yes all in by 2000 RPM.

In an effort to cure an off idle stumble I richened the carb's initional shot 10 ways from Sunday, to no avail. Put all that back to stock and tried increasing base timing, that cured the off idle stumble. I kept giving it more timing waiting for the engine to labor. It almost never did. It does not buck the starter hot or cold, I arrived at the 25° base timing by pulling out the dizzy, closing the window in the Mopar Performance dizzy a little, Set the total timing back to 35°, and the base just fell in at about 25°. Thats where I left it.

No 4 corner idle on the 670. Air bleed restrictors? I will have to do a little research and see if they are adjustable on the SA670?

My guess is it is lean at idle, or the boosters are dripping fuel at idle.  How many turns out from fully seated are the idle mixture screws?  If you continue to turn the idle mixture screws out will the mixture go rich enough to cause a drop in idle rpm?
If the primary boosters are dripping fuel at idle then you need to fix that.  I would think with 30 degrees initial timing, and the vacuum, that this is not the problem.  However 850 idle rpm is a tad high.
If the mixture screws won't richen the mixture enough to cause an idle rpm drop, then I would open up the TQ's IFR's about .003 inch.  If they are currently 0.034" then enlarge to 0.037".  TQ's were emission era carburetors and were lean with the stock stuff.  Using today's fuel, and different cams, intks, etc... only makes it worse.

Idle mix screws are a about 1 1/2 turns out give or take. Coming out more will make the idle get rough and start to drop, noticably rough with another 1/2 turn out. I adjust the mixture screws till the vacuum stops rising, the needle on the gauge smooths out right at that point. Any richer and the needle starts to drop. I have not seen any dribbling from the boosters.   

After the trip to Vegas I will rig a piston stop and verify TDC. I have tried to move the outer ring on the damper with my giant screw driver. It is solid, no flex. But it still could be off I guess.

On a side note, The engine is starting to burn oil. I saw it on the chassis dyno videos from a couple of weeks ago at the HEMI show. Lots of blue smoke out the tail pipes on deceleration. It did it after each pull. Also when just idling in the garage for an extended period. like when messing with the carb, it will start to smoke out the tail pipes. Valve guides seals maybe? 

I noticed the smoke as well.  Could be the seals, and that is the simplest thing to look at and do.  Usually the guides are worn as well.

The off idle stumble might be fixed with opening up the idle feed restriction, verses putting in a bunch of timing. The near instant, light throttle, off idle hesitation is often times due to lean idle and transition, not the squirter, if that is what yours was doing.  The last SA I worked on had this same stumble.  It would also show up if you blip the throttle in neutral.  99% of people you ask will say squirter. 

I dont think the sa series is user friendly for modifying the ifr. He would have to drill them out. If memory serves me, the 670 orifice is .026, stepping up by .002 should be more then enough IF he confirms there are no underlying issues(powervalve, throttle blades, etc) i cant see why a 670's idle circuit cant handle a mild 360?

[BSB67]

Make sure I understand. Initial timing is 30°, full advance is 34° in at 2000 rpm.

I would check, if you haven't, to make sure that the timing is not moving in between neutral and in-gear engine speed.  I.e. check in-gear timing.  Although this is not going to fix stink.

I wonder if that much initial timing is too much for your motor.  I doubt that that would effect stink, but I would try less initial, just too see.

Does the 670 have four corner idle? If you think you have the mixture screws as good as they are going to get, I would maybe try larger idle air bleeder restrictors.

Idle and in gear, timing stays the same. I cleaned off all the old sharpie marks that were on the damper and remarked it in 10° BTDC increments. Base timing is about 25°, total about 35°, and yes all in by 2000 RPM.

In an effort to cure an off idle stumble I richened the carb's initional shot 10 ways from Sunday, to no avail. Put all that back to stock and tried increasing base timing, that cured the off idle stumble. I kept giving it more timing waiting for the engine to labor. It almost never did. It does not buck the starter hot or cold, I arrived at the 25° base timing by pulling out the dizzy, closing the window in the Mopar Performance dizzy a little, Set the total timing back to 35°, and the base just fell in at about 25°. Thats where I left it.

No 4 corner idle on the 670. Air bleed restrictors? I will have to do a little research and see if they are adjustable on the SA670?

My guess is it is lean at idle, or the boosters are dripping fuel at idle.  How many turns out from fully seated are the idle mixture screws?  If you continue to turn the idle mixture screws out will the mixture go rich enough to cause a drop in idle rpm?
If the primary boosters are dripping fuel at idle then you need to fix that.  I would think with 30 degrees initial timing, and the vacuum, that this is not the problem.  However 850 idle rpm is a tad high.
If the mixture screws won't richen the mixture enough to cause an idle rpm drop, then I would open up the TQ's IFR's about .003 inch.  If they are currently 0.034" then enlarge to 0.037".  TQ's were emission era carburetors and were lean with the stock stuff.  Using today's fuel, and different cams, intks, etc... only makes it worse.

Idle mix screws are a about 1 1/2 turns out give or take. Coming out more will make the idle get rough and start to drop, noticably rough with another 1/2 turn out. I adjust the mixture screws till the vacuum stops rising, the needle on the gauge smooths out right at that point. Any richer and the needle starts to drop. I have not seen any dribbling from the boosters.   

After the trip to Vegas I will rig a piston stop and verify TDC. I have tried to move the outer ring on the damper with my giant screw driver. It is solid, no flex. But it still could be off I guess.

On a side note, The engine is starting to burn oil. I saw it on the chassis dyno videos from a couple of weeks ago at the HEMI show. Lots of blue smoke out the tail pipes on deceleration. It did it after each pull. Also when just idling in the garage for an extended period. like when messing with the carb, it will start to smoke out the tail pipes. Valve guides seals maybe? 

I noticed the smoke as well.  Could be the seals, and that is the simplest thing to look at and do.  Usually the guides are worn as well.

The off idle stumble might be fixed with opening up the idle feed restriction, verses putting in a bunch of timing. The near instant, light throttle, off idle hesitation is often times due to lean idle and transition, not the squirter, if that is what yours was doing.  The last SA I worked on had this same stumble.  It would also show up if you blip the throttle in neutral.  99% of people you ask will say squirter. 

I dont think the sa series is user friendly for modifying the ifr. He would have to drill them out. If memory serves me, the 670 orifice is .026, stepping up by .002 should be more then enough IF he confirms there are no underlying issues(powervalve, throttle blades, etc) i cant see why a 670's idle circuit cant handle a mild 360?

Yes to everything, except the 0.026" IFR.  That I just don't know.

[Paul G]

I tried using the lean drop method, whatever that really is? I adjusted the mixture screws the way I normally do for the smoothest lean Idle. Then back in just a hair at a time, the engine idles just a little rough like this, air fuel is about 12.5 instead of 12.00. But most of the stink is gone. The little bit of rough idle is not terrible. Still about 750 drive.

[Bronzedodge]

Hi Paul,

Hollys- my money would be on a bad power valve.  Bad part about that would be the need for gaskets and another power valve to change it.  I know Holly says it's a rare event for one to fail, but if there ever was a miss or a reverse flow through the carb, there is a chance.

[flyinlow]

Your kind of at the same compromise I made. I have a QF 780 in a 440. The engine idles smoothest/best vacuum at about 12:1 A/F according to the sensor in the left header. But it stinks. lean slightly to 13:1 ,little rougher but I can walk behind the car idling easier. Like most Holley style carbs , its good that they are easy to tune, because you get to do it a lot. Spring ,summer, fall, winter.