quit idling in gear, carb just needs a cleaning, right?

[diymirage]

hey guys
car is a 71 duster, with a 408 small block on in and a preform 750 double pumper

she was idling fine up until a few days ago 8-900 in neutral, 6-700 in gear

a few things happened over the last week which all relate to fuel delivery so let me run this by you guys and see if am correct

1 I swapped valve covers left to right. the car is running a PCV valve on one side and a breather on the other. I checked to make sure the PCV is still connected right, it is, the hose is just routed different

2 I went to install a fuel pressure gauge on my car, and when I did I killed the fuel line. picked up a cheap chrome and screwed that on up too. in the process of "making it work" I eliminated the fuel filter

3 I played with the float level a bit, trying to get things right. I went out to the track two weeks ago and messed with them there, and been messing with them ever since (if someone knows where the level should sit, under the glass, middle glass, front even with the back, let me know)

4 I replaced the chrome line with a fancy AN style one and installed a new filter and my gauge, I was running 3 PSI

5 today, I installed a high pressure mechanical pump and a regulator
set the pressure to 7 PSI

throughout all this, the engine will not idle well in gear
not very well in neutral either, but I can set it to idle with the butterfly screw, but once I drop it in gear it wants to die
I have not tinkered with the normal idle adjustment screws (bleeders are they?) because

A I don't know what I'm doing
B I don't have a vacuum gauge
and C, I think during the time I ran it without the fuel filter I may have clogged up an idle circuit

what do you guys think ?
and if it is a clogged circuit, what do I clean?
(pretty new to this whole 4 barrel carb stuff)

thanks guys

 

[TrailBeast]

On a carb I'm starting from scratch on I screw the idle adjustments screws all the way in counting the turns it takes to bottom out lightly.
Then take them all the way out and blow air in them (like at least 20 lbs) and run the screws all the way in and back them out the amount I counted when I first ran them all the way in.
This puts them back at the same amount they were.

If this doesn't do it then it may be time to pull it and disassemble for cleaning.
There have been times that closing the choke all the way by hand at the same time I move the throttle to wide open controlling the RPM's with the choke so it can't rev too high has also cleared idle circuits, but it doesn't work 100% of the time.
It's just the first attempt I make before removing the screws and blowing the idle circuits out with air.
It is common for a carb to get crap in it when messing with or changing fuel lines or fittings.

Approximate center of the sight glass is your fuel level.

 

[diymirage]

Thanks for the reply
There is no choke on it, so I'll have to try to identify the idle adjustment screws and try blowing them out

 

[TrailBeast]

These

 

[AJ/FormS]

What's your initial timing?
If you run too much initial, your butterflies will be too far down the transfer slots. Then with the sudden drop in airspeed when you put it in gear, the engine may not recover.The loss in rpm leads to a loss of vacuum which might lead to the PV opening, but its to late. Maybe it dumps a bit of gas,maybe not. Then you have to crank it a bit to get her going again.
See below

 

[diymirage]

Gotcha, I got 4 of those
I think initial timing is 15 degrees

Considering when this happened I'm pretty sure it is a crud issue, so I'll try that first

 

[gtsdude]

I would bring fuel pressure down to 6-6.5 at the most. Holley says no more than 7 with 6 being ideal. You have a proform carb or center section on a Holley carb? Proform recommends 1/2 up the sight glass, Holley recommends bottom of sight glass. I recently swapped cams and couldn't get it to idle under 1k, until I noticed 7psi on the fuel pressure gauge and fuel at the top of the sight glass, too much pressure and was pushing fuel past the needle and seat. I set fuel pressure at 6psi, idle came down and float level was at bottom of the sight glass. I'm still not sure how the fuel pressure got that high, I never touched it from last year.

 

[diymirage]

thanks GTSdude, the entire carb is a proform unit, with the sight glass, not the plugs

I went with 7 PSI since that was the number on my dyno sheet, but ill run her down to 6

I wonder if you installed you eccentric hub slightly off center when you swapped cams?
that is what powers the pump, afterall

 

[gtsdude]

Electric pump on mine, forgot to mention that. I did notice last fall it wanted to idle up the last time I drove it, the regulator probably needs a rebuild, its about 10 years old.

 

[diymirage]

quick update
I pulled the car into the garage (to give you an idea of how cold the engine was)

took out all four idle screws, shot some carb cleaner in there, some compressed air, more cleaner, more air and put the screws back in
three of the screws were set at 3/4s, but one was set at 1 1/8
I was very tempted to put them all in at 3/4s but decided to put it all back where I found it

cranked it over and fired right up
she idled at 450 in neutral an when I dropped it in gear that dropped to 400

so I think I can say mission accomplished

if I get a chance to drive her today ill check to see where idle sits with a warm engine and crank it up to about 6-700 in gear

Electric pump on mine, forgot to mention that. I did notice last fall it wanted to idle up the last time I drove it, the regulator probably needs a rebuild, its about 10 years old.

depending on when and where it was made, 10 years isn't too bad

 

[mguner]

If you removed a filter you likely got trash in the needle and seats. Often happens when removing or changing fuel filter. Some high pressure air will usually flush it out.....