"Factory" vacuum leak???

[Creedmoor]

Can't figure this out. Holley 1850-3 with a huge vacumn leak from the electric choke. When I rebuilt this carb (see pics) the little screen inside the brass fitting was caked up with soot. After cleaning it became a huge vacuum leak and you couldn't adjust the idle below 800rpm. So I plugged it and everything is fine. So, what is this screened in leak supposed to do? Is there a part missing???

 

[pishta]

Isnt that the exhaust heated choke stove dealio?

I always called the PCV a factory vacuum leak...

Put a piece of clear tape over the hols and back over the threaded fitting and screw the brass back on, maybe thatll seal it for good.

 

[Big Jim]

The fitting was originally used to connect a tube from the exhaust manifold/header to the choke housing. Idea was to use the heat transfer to open the choke faster in cold weather before electric chokes became commonplace.

 

[cudamark]

Isnt that the exhaust heated choke stove dealio?

I always called the PCV a factory vacuum leak...

Put a piece of clear tape over the hols and back over the threaded fitting and screw the brass back on, maybe thatll seal it for good.

Yeah, it was for the hot tube that went through the exhaust manifold on some models. Just cap it off if you're going to use the electric choke.

 

[Creedmoor]

Thanks guys. How in hell could the guy that installed/rebuilt this thing have left it open to the air like that and not noticed? After I capped it, I could actually adjust my idle!

 

[cudamark]

The same way you did....he just didn't know. Glad it was a simple fix.

 

[65Val]

Thanks guys. How in hell could the guy that installed/rebuilt this thing have left it open to the air like that and not noticed? After I capped it, I could actually adjust my idle!

Its supposed to be open, with a restriction. If it isn't, you'll burn up the choke heater coil.

I think you've developed a leak somewhere else,and after cleaning, this "leak" was making the most noise, so you naturally thought that was the problem.

Just curious...how far propped open do you have the secondaries?

 

[67Dart273]

Uh.................from the horses mouth:


"Do not block the fresh air intake"


I would suggest that maybe you have something wrong or missing, is the vacuum piston in the choke housing? Seems to me there are some drive in plugs, and an O ring, anything else that might be leaking?

http://www.google.com/url?sa=t&rct=...wOmiDg&usg=AFQjCNE4vDhHai3sb5K7oGIQyYTM0tS-4Q

 

[65Val]

Yeah...what ^^^^he^^^^ said!!!

 

[Creedmoor]

Crap! With this "fresh air intake" installed I can't get my idle down below 800 no matter how far I turn in the mixture screws and with the idle speed screw not touching anything. Also, it never returns to within 75-100 rpm of where it started if you blip the throttle. All linkage moves freely. Timing is about 5 degrees BTDC - if I put it anywhere near where I want it at about 8-10 my idle is even higher. New gaskets all around (carbwise) and there are only two vacuum hoses - PCV (new hose and valve), and vacume advance. Vac advance makes no difference to this problem if it's plugged or unplugged. I've sprayed carb cleaner, propane and startting fluid everywhere to try and find this effin vac leak I KNOW I have. AARRGGGHHH!!! A little help pretty please.

 

[65Val]

Crap! With this "fresh air intake" installed I can't get my idle down below 800 no matter how far I turn in the mixture screws and with the idle speed screw not touching anything. Also, it never returns to within 75-100 rpm of where it started if you blip the throttle. All linkage moves freely. Timing is about 5 degrees BTDC - if I put it anywhere near where I want it at about 8-10 my idle is even higher. New gaskets all around (carbwise) and there are only two vacuum hoses - PCV (new hose and valve), and vacume advance. Vac advance makes no difference to this problem if it's plugged or unplugged. I've sprayed carb cleaner, propane and startting fluid everywhere to try and find this effin vac leak I KNOW I have. AARRGGGHHH!!! A little help pretty please.

Ok...lets start with the basics...

Does the throttle cable have a little slack in it at idle?

How far is the "secondary throttle screw" holding the sec's open?

All vac ports plugged or hooked to something?

Is the choke coming off completely , including the fast idle cam?

Kickdown linkage not holding the throttle open?

Get back to us on these.

 

[RustyRatRod]

That has nothing to do with the engine's vacuum source. IF there is a vacuum leak from THERE, the only thing it can be is a malfunction with the vacuum assisted choke pulloff piston, or some dumbass has removed the piston. Also, the only reason Holley says not to stop that fittin up is when you use it as a hot air choke as it was originally designed. Once you convert it to an electric choke, you can leave it open or close it off. It makes no difference whatsoever. Whoever wrote that article for Holley was a few bricks shy of a fuckin load. TONS of Holley carburetors come FROM THE FACTORY with electric only chokes, and NO hot air tube AT ALL and they don't overheat. Somebody needs to put the crack pipe down.

 

[USCG CHARGER]

I ran mine without any vac lines or pcv lines.... I guess I need to learn what I don need and what I don't need.

 

[jos51700]

That has nothing to do with the engine's vacuum source. IF there is a vacuum leak from THERE, the only thing it can be is a malfunction with the vacuum assisted choke pulloff piston, or some dumbass has removed the piston. Also, the only reason Holley says not to stop that fittin up is when you use it as a hot air choke as it was originally designed. Once you convert it to an electric choke, you can leave it open or close it off. It makes no difference whatsoever. Whoever wrote that article for Holley was a few bricks shy of a fuckin load. TONS of Holley carburetors come FROM THE FACTORY with electric only chokes, and NO hot air tube AT ALL and they don't overheat. Somebody needs to put the crack pipe down.

You don't want to close it off. It's how the bimetallic spring cools and avoids overheating. The vacuum port also helps the bimetallic spring regulate it's speed in opening/closing relevant to ambient air temperature (Cold air coming through there slows the opening of the spring for longer warmups.)

I JUST installed an electric choke on my Dart and went through this, like 3 weeks ago. A call to Holley verified what the directions said.

I also had the EXACT same problems listed by the OP. Cause: No throttle slack.

65Val is, in my opinion, on the right track for diagnosis.

 

[67Dart273]

Whoever wrote that article for Holley was a few bricks shy of a fuckin load. TONS of Holley carburetors come FROM THE FACTORY with electric only chokes, and NO hot air tube AT ALL and they don't overheat.

Is it possible that you are a Holley engineer?

Is it possible that you are NOT?

Is it possible that the ones with no air tube use a different heater?

Is it possible that there is a vent in the housing that you are not aware of?

That article came FROM Holley. Personally, I tend to believe it when a manufacturer says something.

 

[Creedmoor]

I'm so confused.........

 

[RustyRatRod]

Is it possible that you are a Holley engineer?

Is it possible that you are NOT?

Is it possible that the ones with no air tube use a different heater?

Is it possible that there is a vent in the housing that you are not aware of?

That article came FROM Holley. Personally, I tend to believe it when a manufacturer says something.

Ok dude. Then explain why in the world millions of Holleys are sold with electric chokes that have no hot air provision whatsoever and they don't overheat the choke. Explain all the BILLIONS of other carburetors all over the world with electric chokes and NO hot air tubes that do not overheat the electric choke coil. The hot air tube serves one purpose. To funnel hot air INTO the hot air choke from a hot air source such as an exhaust manifold. That's ALL that tube is for. I don't give a rat's butt what Holley engineer says what to who. Chances are, I've been building Holleys longer than most of those engineers anyway and so have a LOT of other people. Just because they work for Holley, doesn't make them Gods. Are you trying to tell us that somehow putting an electric choke thermostat onto a hot air choke housing suddenly breaks all of the laws of physics in the universe and in that one spot things happen differently? Yeah, ok. I got some ocean front property in Kansas I will sell you. Once you make the conversion from the hot air to electric on a Holley, the hot air housing is no longer relevant. Don't believe me? Ok genius, how bout this? What if I decide to replace the WHOLE hot air housing with a WHOLE electric housing? They ARE different, you know? The electric housing has NO opening to the atmosphere WHATSOEVER. NONE. ZERO. ZILCH. You be a little sheep if you want to, and follow right along. I know differently and I don't give a FRIG what Holley or anybody else says. Oh yeah. Merry Christmas. LOL

 

[67Dart273]

Ok dude. .................. millions of Holleys are sold the BILLIONS all over the world ................NO hot air tubes . ..................................................I don't give a rat's butt what Holley engineer says what to who.

You've made it intensely clear that you don't give a rat's butt and YOU HAVE NOT showed any concrete evidence that you are correct and Holley is incorrect.

So my questions still stand

 

[RustyRatRod]

You've made it intensely clear that you don't give a rat's butt and YOU HAVE NOT showed any concrete evidence that you are correct and Holley is incorrect.

So my questions still stand

I will answer the only question that's relevant. The electric choke conversion from Holley uses the SAME part number choke thermostat for the hot air choke that the factory electric choke uses. THAT is a fact. Above any beyond that, I'm not really carin too much what you think. But Merry Christmas anyway.

 

[pishta]

Check this out from a "vette forum, guy may know what he is talking about..."Yes, there are tubes and vacuum connections on electric choke carbs...

On an automatic choke (such as an electric choke), you have to have a choke pulloff (aka "vacuum break") in order to crack the choke open when the engine starts. Holley used 2 styles of choke pulloffs:

1. First style is the external choke pulloff, mounted very similar to a Q-Jet. This uses an external vacuum diaphragm with a vacuum hose running to a manifold vacuum source on the carb. When the engine starts, engine vacuum pulls on the choke pulloff and cracks the choke open about 1/4".

2. Later style, and common on most of the "generic" Holley carbs is an internal vacuum break piston mounted inside the electric choke housing. The piston receives vacuum from an internally drilled hole that goes from the piston cavity into the carb body. Many carbs, if not originally equipped with an automatic choke, do not have this passage drilled in the carb. If mounting an electric choke to such a carb body, you have to do the machine work to create the vacuum connection, otherwise you will get nothing but massive flooding of the engine on cold starrt.

Some other carbs, in addition to the vacuum connection for the choke pulloff, will also have a vent tube (not a vacuum tube) running from the choke housing to the airhorn area of the carb. This tube is only to provide ventilation of the choke housing to prevent it from overheating from the hot electric coil. It draws in a small amount of clean air from the airhorn area of the carb and pulls it through the vacuum break piston leak path. Since this is not a vacuum tube (only a clean air vent tube) you can replace the tube with a filter "sock" over the choke housing inlet. Most later model Holleys with electric chokes simply use a filter screen over this inlet, and do not use the tube running to the airhorn area. But it is imperative that you establish the vacuum bleed source inside the housing so that air will be pulled through the choke housing. Otherwise, the housing can get hot enough to damage the choke coil assembly.

Lars

Seems there is some sort of ventilation in a coil heated choke, but is shouldnt be a vacuum leak unless the little piston in the choke cavity is not doing what its is supposed to do?

 

[65Val]

Like this....


Its not a HOT air tube...its cool air.

 

[65Val]

Ok. Now that we've beaten the electric choke subject to death (hopefully), could we get back to this gentlemen's original question???

Creed....have you checked out any of the things in my post #11 above?

 

[George R]

I bet the piston in the carb has been removed and allowing too much air into the choke housing causing the arratic idle.
Now, having said that, is the OP absolutely SURE there are no other vacuum leaks on the engine?
Is the PCV valve the correct one for the engine?
Are the correct heat range plugs installed? If too cold a plug is used the engine won't idle correctly.

In order to eliminate all this hokus-pocus (if it was my car it would have been done already) you can always remove all this electric/vacuum automatic choke control BS and install a manual choke cable. This way you can plug all these mystery holes and be done with it.

George