440 six pack high idle

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Righty Tighty

Righty Tighty

Blame it on the dog
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****Disclaimer -- I have posted this on the E Body forum, which is great, but quite honestly there doesn't seem to be as much activity over there as there is here****

Hey all, I brought home a 74 Barracuda a couple weeks ago, and she's fitting right in. I'm doing my best to give her a thorough inspection before *officially* getting out on the road, and naturally there have been some bumps along the way.

I got it to start after flushing the gas tank, new lines, new plugs, oil, fuel filter and sending unit sock. As the choke opens, the idle steadily increases until what sounds like about 2500 rpm. I haven't connected the tach to find out exactly what the rpm is. I gave a quick check for vacuum leaks, and then checked the initial timing. Over 25 degrees initial (vacuum advance disconnected and plugged). I bumped the timing down to about 10 advanced so that it was drivable enough to flush and bleed the brake system, but even at 10 it sounds a bit high, like maybe 1500 rpm.

The curb idle screw is about as far out as it will go, idle mixture screws are 2 turns out each. I haven't inspected how much of the transfer slots are exposed, but I can see that the outboard throttle plates don't appear to be sticking open. I haven't looked at the distributor yet. I disconnected the brake booster vacuum line and plugged it, no difference.

Here's what I know about the setup that might be relevant:
440 six bbl, 727, headers, power brakes. PCV port is capped, vacuum advance runs to ported vacuum, from what I can tell the fast idle cam isn't hanging up.

I think this blue plastic piece is the fast idle cam, which has a broken bit. I keep hearing about the metal tab on the fast idle cam that needs to be bent, but I don't know where to find this dang thing.
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What else can I check for?
 
Check the base gaskets and bores, sometimes they can be off and hold the throttle open slightly.
 
I would pull the carbs and clean and inspect carefully, could have a crack also never know who was in there.
 
It's very very simple in theory, maybe not so easy to find. An engine HAS to have air to run. If you kill the air, "it won't." ^^As above^^ and look everything over carefully. Vacuum leaks, carb gaskets, all throttle blades, vacuum hoses, leaks at the intake--to head, missing plugs, EVEN A CRACKED INTAKE

If you are about to give up, pull the outer carbs, make block off "gaskets such as pepsi can pieces, and set the carbs back down to seal them off, leaving only the center carb
 
Thanks so much. I thought for sure it was either timing or vacuum, but from what I have done so far, no results. I was hoping to not have to pull the carbs for this, but I think it might be the best plan of action, especially since I don’t know the history.
 
Then don't pull the carbs yet. unless you've disconnected the throttle cable and BOTH outboard carburetors, you've not done all the diagnosis you can do yet.
 
It's also wise to upgrade to the adjustable outboard carb metering plates. I went through all this on my buddies 69 Super bee took a while but damn was that thing cool
 
thesiren74 said:
It's also wise to upgrade to the adjustable outboard carb metering plates. I went through all this on my buddies 69 Super bee took a while but damn was that thing cool
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I’m definitely expecting this to take some time. I finally got to the point where I can just click the key on my Scamp and it lights right off, boy what a feeling. Apparently it was time for another project...
 
I see some questionable advice. I would start by disconnecting the outboard rods just to make sure that the secondary carbs are closed completely during idle . Start the motor and check for any change.Also make sure that the primary carburetor butterfly is moving freely and not getting stuck partially open.but my number one concern would be that the outboard carburetor air idle is not adjusted properly which requires you to remove the outboard carburetors and check if the lead plugs have been removed at the front of the base of the carburetor. My guess is someone has open them up. Return to factory setting ,add a quarter to half of a turn more if you're running a hotter setup.
 
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The outboard carbs have an idle circuit. If you block them off from the intake the car will not idle well at all. You will be causing more problems.

don’t disconnect the outboard Mechanical linkage and drive the car. That linkage closes the carbs.

Male sure the outboards are closed and disconnect the vacuum lines so they will not open. then run and drive the car and see what happens.

Make sure the throttle cable isn’t holding the center carb open. Disconnect it and leave the return spring on and run the car and check the idle speed.

How much idle vacuum does this have? How big does the cam sound?
 
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Are these original carbs? If not if they were built in the 2,000's they had a bad internal delamination problem.
 
They’re not original to the car, it was a 318 car. The block is a ‘69, the intake is a cast aluminum Edelbrock, so that’s definitely not original to the engine. How can I determine when the carbs were made?
 
Righty Tighty said:
They’re not original to the car, it was a 318 car. The block is a ‘69, the intake is a cast aluminum Edelbrock, so that’s definitely not original to the engine. How can I determine when the carbs were made?
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Has to be a code on them, if you take the bowls off you'll find out real quick
 
413 said:
The outboard carbs have an idle circuit. If you block them off from the intake the car will not idle well at all. You will be causing more problems.

don’t disconnect the outboard Mechanical linkage and drive the car. That linkage closes the carbs.

Male sure the outboards are closed and disconnect the vacuum lines so they will not open. then run and drive the car and see what happens.

Make sure the throttle cable isn’t holding the center carb open. Disconnect it and leave the return spring on and run the car and check the idle speed.

How much idle vacuum does this have? How big does the cam sound?
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I’m gonna do some testing tomorrow and report back with results. I haven’t checked idle vacuum yet, but I will.

I am enough of a novice to where I struggle to find the right terms to describe how the big the cam sounds. Let’s just say it definitely sounds bigger than the mild cam in my Scamp, but tame enough to be a street cam. Maybe street/strip? I hope that makes sense. The engine’s “build sheet,” if that’s what you wanna call it, just says what the mechanic did to the engine, not what he put into it. I’m a little bummed about that, because I have no way of knowing exactly what cam, springs, lifters, etc are in the engine unless I tore it apart. And even then I don’t think I’d be able to tell what the cam was just by looking at it.
 
Im working on my sixpack setup right now too. Heres an honest truth about most sixpacks.

They’ve all been fiddled with or touched at some point.

Most notoriously is the fuel distribution plates inside the outboard carbs. Notice how they do not have metering blocks? Under the bowls of each is a factory tuned plate with a precision drilled holes at the bottom. These essentially act as “jets” but are not really meant to be messed with. Well guess what? Most “Shade tree guys” end up drilling those out “a size up” to compensate for power adders they’ve put on the motor. A good tell tale for this is light scoring in the channels through the bottom holes where the drill bit went. Not only did they affect the primary circuit but these plates also feed the idle circuits from the same holes!

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Your best solution to this is the Promax Jettable plates above. they replace the Original holley ones that came in these carbs. They aren’t terribly expensive either.

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Like mentioned above the promax rear base plate is also worth the money. It turns the tuning needles out at a 45° angle so you can tune the rear carb without having to remove it. Here i have it mounted on the front flange for picture purposes but it is made for the rear carb so you can get to the screws.

Edit: I noticed i posted a picture with the throttle shaft and butterflies installed incorrectly. Yes i fixed this. Classic case of too excited and slapped it together.

I realize this is long winded but honestly sixpacks require it.
 
To say that Mopar six packs must have promax plates is ridiculous there is hundreds of beautifully tuned six pack that have been raced to the top of their divisions or brackets and perform beautifully on the street without those plates and to slander all of them by calling them shade tree mechanics. Wow
 
K.O. SWINGER said:
To say that Mopar six packs must have promax plates is ridiculous there is hundreds of beautifully tuned six pack that have been raced to the top of their divisions or brackets and perform beautifully on the street without those plates and to slander all of them by calling them shade tree mechanics. Wow
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When you have better options out there you might as well use them. Factory plates that have been tuned/modified cannot be tuned back to factory because you are physically removing material, so it will never run correctly. At least not from engine to engine. You have no idea what kind of engine they were modified for.

You’re right its not fair to call them all shade tree mechanics. But it wouldn’t matter if it was me or one of the ram charger guys, if you modify these plates there’s no turning back. With the promax plates you can jet up or down until its right for you. Just a quality of life suggestion.
 
K.O. SWINGER said:
To say that Mopar six packs must have promax plates is ridiculous
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Also it was a suggestion, not a requirement to have a clean running sixpack. If he opens them up and they haven’t been touched? Great! But lets say his engine wants more fuel in the outboards at WOT? He’s stuck with what he has or modifying his plates. Worst case scenario you drill it too big and now you’re looking for new plates. Again just a suggestion to save some frustration and time. Promax plates are a quality of life addition to any sixpack setup, street or strip.
 
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