Holley 2210 idle issues

[ChryslerCaptain]

I have a 72 Newport 400 with a NOS Holley 2210 and it idles way to high around 1800RPM in park/neutral when I put it in gear it calms down a little bit not much. I’ve played with both idle screws it’s currently as set at the lowest idle it will take without dying still 1800rpm does anyone have an idea what could be the problem?
I know the timing and air to fuel ratio is correct. I’ve also checked for vacuum leaks, but had no success.

 

[413]

Well check further for vacuum leaks. disconnect The brake booster and plug the fitting.

 

[65Port]

Throttle shaft bushings worn? Is the throttle cable binding holding it off the stop?

 

[CBODY67]

Upon further consideration . . . 1800rpm? That's higher than the fastest fast idle speed spec for that car and carburetor. If the car was put into gear at that speed, the car would LURCH forward against the brakes (fully applied) and the car would then try to move forward. Not to forget how forcefully the transmission would go into gear!

Now, how long has this been going on? Gradually building to this point or "all of sudden"?

Here's something else to look at . . . considering the fast idle cam and speed adjustment screw is on the passenger side of the carburetor, might the fast idle cam be hung or broken such that it is restricting the cam from dropping down (due to gravity) to its lowest speed position? When that cam and screw are holding the idle speed higher, you can turn the driver's side idle speed screw all you want and it will not affect anything. Nor will the idle mixture screws (as past about 1200rpm, the idle mixture screws have no affect as the carburetor is mostly operating on the main system
anyway).

From what I know about the Holley 2210 carburetors, if the carburetor is functioning correctly, a carburetor-related malfunction will not cause the situation you describe by itself. So I strongly suspect something else has happened (due to age, if nothing else). As in a BIG vacuum leak somewhere. The biggest vac leak might be from a power brake vac line which has cracked, or possibly a pcv rubber line which has cracked or broken. The smaller vac lines going to the various things (as the hot air diaphram in the air cleaner snorkel, distributor vac advance unit, automatic choke pull-off, or the HVAC vac supply) will result in a vac "leak", but not a big one that would cause really elevated idle speed. Rough running at idle, yes, but not a significant increase in base idle speed. SO . . . DO check every vac hose which connects to the carburetor to see that they are plugged onto the carburetor and THEN check each one for cracks or age-related issues.

ALSO, get a wrench (like a 12-point combination wrench) of the correct size and SNUG down the carburetor mounting nuts. Just a snug, no more than that!

If, perchance, the power brake booster is failing, that will be evidenced by a harder pedal and an engine miss when the pedal is depressed. No miss without the pedal depressed, usually.

Please check the things I and others have mentioned. Let us know what you find, please.

CBODY67

 

[ChryslerCaptain]

Upon further consideration . . . 1800rpm? That's higher than the fastest fast idle speed spec for that car and carburetor. If the car was put into gear at that speed, the car would LURCH forward against the brakes (fully applied) and the car would then try to move forward. Not to forget how forcefully the transmission would go into gear!

Now, how long has this been going on? Gradually building to this point or "all of sudden"?

Here's something else to look at . . . considering the fast idle cam and speed adjustment screw is on the passenger side of the carburetor, might the fast idle cam be hung or broken such that it is restricting the cam from dropping down (due to gravity) to its lowest speed position? When that cam and screw are holding the idle speed higher, you can turn the driver's side idle speed screw all you want and it will not affect anything. Nor will the idle mixture screws (as past about 1200rpm, the idle mixture screws have no affect as the carburetor is mostly operating on the main system
anyway).

From what I know about the Holley 2210 carburetors, if the carburetor is functioning correctly, a carburetor-related malfunction will not cause the situation you describe by itself. So I strongly suspect something else has happened (due to age, if nothing else). As in a BIG vacuum leak somewhere. The biggest vac leak might be from a power brake vac line which has cracked, or possibly a pcv rubber line which has cracked or broken. The smaller vac lines going to the various things (as the hot air diaphram in the air cleaner snorkel, distributor vac advance unit, automatic choke pull-off, or the HVAC vac supply) will result in a vac "leak", but not a big one that would cause really elevated idle speed. Rough running at idle, yes, but not a significant increase in base idle speed. SO . . . DO check every vac hose which connects to the carburetor to see that they are plugged onto the carburetor and THEN check each one for cracks or age-related issues.

ALSO, get a wrench (like a 12-point combination wrench) of the correct size and SNUG down the carburetor mounting nuts. Just a snug, no more than that!

If, perchance, the power brake booster is failing, that will be evidenced by a harder pedal and an engine miss when the pedal is depressed. No miss without the pedal depressed, usually.

Please check the things I and others have mentioned. Let us know what you find, please.

CBODY67

Thank your for all the advice I will definitely check through everything you said. I doubt it’s a “age” issue it’s a fresh motor (1700 miles) Like previously mentioned it’s a New old stock carb. When I 1st got the engine back together and running (with original factory carb) it ran like total crap. So I got the NOS carb and have had the high idle issue since.

 

[CBODY67]

The "age" issue is related to rubber hoses and such, not the carb per se.

Was the carb in a genuine Holley box? Was it also for a 400, too?

The only "age" issue with the carb itself is that people generally over-tightened the wing nut holding the air cleaner on. Over time, that over-torque would put an upward pull on the air cleaner stud, which would deform the air horn upward, so the gasket on the rear of the float bowl was compromised. Which would ALSO mean the vac to the power valve was lost, which mean the carb was operating with "mixture enrichment" at all times and decreased fuel economy. Chrysler came out with a TSB and "fix kit" for that issue in about 1974 or so.

CBODY67

 

[ChryslerCaptain]

The "age" issue is related to rubber hoses and such, not the carb per se.

Was the carb in a genuine Holley box? Was it also for a 400, too?

The only "age" issue with the carb itself is that people generally over-tightened the wing nut holding the air cleaner on. Over time, that over-torque would put an upward pull on the air cleaner stud, which would deform the air horn upward, so the gasket on the rear of the float bowl was compromised. Which would ALSO mean the vac to the power valve was lost, which mean the carb was operating with "mixture enrichment" at all times and decreased fuel economy. Chrysler came out with a TSB and "fix kit" for that issue in about 1974 or so.

CBODY67

Yep genuine never used Holley still have the “retro” box it came in! The eBay seller said he bought it for his 400 in his truck but opted for a four barrel instead.

 

[413]

Make sure the choke and fast idle linkage is not keeping the throttle from returning to idle and holding the rpm up. I’ve seen NOS over the counter carbs that were assembled wrong and do this.

 

[66 Monaco 500 365]

Is there slack in the throttle cable?
Just "thinking out loud" (on the keyboard)