Team Camaro Tech banner

1 - 9 of 9 Posts

·
Registered
Joined
·
3,692 Posts
Discussion Starter #1
The 2bbl Holley list 80179 on my '83 F-150 is about to drive me nuts. I've been battling an issue with the idle speed and an off idle stumble for a while now. I got the stumble fixed this weekend (along with a minor fuel leak) after replacing the accel pump diaphram that was rock hard and cracked. I have made no headway against the excessively high idle speed though. When the engine is at ambient temp's, the electric choke does its thing and the engine start easily enough, but then the rpms climb to anywhere from 1100-1500 rpms. Once the engine is warmed up, I cannot get the choke to release at all. I can manually release the choke by hand under the hood, but as soon as I touch the gas peddle the rpms immediately jump back up high. It makes driving this thing a real pain in the arse because it pulls against the brakes hard when sitting at a stop while in gear, plus the high rpms really reduce the brakes effectiveness in stop and go traffic. Even with the choke manually disengaged, it still idles at 1000-1100 rpms (800-900 rpms in gear, as long as you don't touch the gas peddle), and will idle no lower in park. The only idle speed adjustment on this thing is from a solenoid controlled, vacuum operated "throttle kicker" that I have completely removed (and plugged off its vacuum line), but there was no change in idle speed at all. I have rotated the choke coil housing as far as it will go but this also had no effect. I even removed the rod that connects to the choke butterfly in the airhorn but that didn't help either. It does appear that someone has been in the carb before...is it possible that they wound the spring in the choke mechanism too tightly? I am flat out of idea's here.

The tuning issue I am having is that the carbs idle mix screws are almost totally unresponsive. At 1000 rpms the engine pulls 15.5" vacuum...considerably less than what I would expect from a bone stock engine. And with the high idle speed, if I don't kill the engine while its in gear, it diesels BADLY. It sometimes even does it just a bit while in gear.

I haven't removed the carb from the manifold yet, but it certainly seems to me like the throttle is open too far, but I can't really tell from looking down the thru the top of the carb as it has these large, weird boosters on it with cross patterns across the tops of them.

BTW, what does a "542" jet equal? I thought all holley jet sizes where 2 digits?
 

·
Super Moderator
Joined
·
32,472 Posts
Time to get another carb, maybe a Model 2300 2-bbl. It reads like you might have a small vacuum leak, throttle plate rods? Broken gasket between the EGR plate and manifold? Carb water heater plate and manifold?

I would think there would be a hidden idle screw because the OE used to go by setting throttle opening with a manometer, as in factory calibration, yada, yada. Remember those times? You can always lower the idle by bending the tab or filing it down.

The OE carb is designed for emissions, meaning the elcectric choke, not a bad thing when they work, XX2 main jets meaning the jets are Close Limit Jets (developed for OEM applications to obtain tighter carb emissions flow limits, jet flow variation between two jets of the same size is reduced by 60% compared to standard jets, and sometimes Holley put in reverse mixture screws, meaning turning the screw in, richens the mixture.
 

·
Registered
Joined
·
3,222 Posts
I think I'm with Ev on the carb. My boy's first vehicle was an old 80something Ford pickup. We rebuilt the carb on it and it was simple as could be. I thought it was a Motorcraft carb but its been a long time, coulda been Holley. That little 302 ran good after we rblt the carb.

No, it was definitely a Motorcraft carb. I think:)
 

·
Premium Member
Joined
·
22,122 Posts
I wouldn't replace the carb quite yet.

I would remove it from the manifold ASAP tho. It is passing too much air. Since the mixture screws are unresponsive (I assume you've taken the limiter caps off?) I've gotta assume the throttles are open too far, rather than that you have a vacuum leak.

Once the carb is in your hands, a way will be revealed to get the throttles set for a square transfer slot, which should fix your problems.
 

·
Registered
Joined
·
3,692 Posts
Discussion Starter #5
I ended up finding that the choke was WAY out of adjustment. Got it set correctly and now I have a 1200 rpm high idle on the choke and, after capping off a manifold vacuum port connected to the fuel vapor recovery system, a solid 600 rpm idle with the choke deactivated :hurray: The choke operates perfectly now...warm it up a bit and a light tap of the throttle is all that is needed to deactivate it. I've got a rock solid 18" idle vac at 600 rpms now.
However, I've still got a pretty bad off idle stumble and a light load surge when cruising around 30mph or so. When I take off from a dead stop, it takes off for about 5 feet, then falls on its face unless I give it more throttle. What do you think...change the pump cam, and maybe step up to a 56 or 58 jet? This thing also has one of those economy/emmisions 2 stage power valves in it (10.5/6.5 I believe). Could this be contributing to the off idle issues I'm having?

So far, strictly highway driving at 65mph, I've managed to get this thing from 8mpg when I got it to 13.6mpg now.
 

·
Super Moderator
Joined
·
32,472 Posts
I had my 7009 Holley (73 Dodge D100 w/360 CID) working good after setting choke.
I also had to lower fuel level.
I also had to increase squirter from OE 25 to 31 to remove of the bog.
Yes, OE dual stage power valve, first stage at 12.5, final stage at 6.5.
Mileage went from 14 mpg to 17.5 mph.
 

·
Registered
Joined
·
3,692 Posts
Discussion Starter #7
I had my 7009 Holley (73 Dodge D100 w/360 CID) working good after setting choke.
I also had to lower fuel level.
I also had to increase squirter from OE 25 to 31 to remove of the bog.
Yes, OE dual stage power valve, first stage at 12.5, final stage at 6.5.
Mileage went from 14 mpg to 17.5 mph.
Did you leave the 2 stage power valve in there, or change to a conventional power valve?

I also wondered if maybe just a larger squirter would cure the off idle/light throttle stumble. Think I should try that first? Is the squirter size marked on there anywhere, so I can know what I am working with?
 

·
Super Moderator
Joined
·
32,472 Posts
Did you leave the 2 stage power valve in there, or change to a conventional power valve?
I left it there.
I also wondered if maybe just a larger squirter would cure the off idle/light throttle stumble. Think I should try that first? Is the squirter size marked on there anywhere, so I can know what I am working with?
Squirter size stamped on it, look halfway between the holes/nozzles and the screwhead. 25 should be OE size. Easiest item to change.

I also played with initial timing.
 

·
Registered
Joined
·
3,692 Posts
Discussion Starter #9
I'll try a squirter swap first then.

Unfortunately, I can't change the initial timing, as it is not adjustable. Depending on what a squirter change does for me, that may be the next obstacle I attack.
 
1 - 9 of 9 Posts
Top