What is the effect of the secondary air door drop amount? What I am referring to, is the amount that the air door opens initially, when the throttle is slammed open all the way. This amount can be adjusted anywhere from no opening to approx .180. This adjustment is made via the choke pull off linkage bending. My question is, what are the effects of a zero opening verses a .180 opening when the throttle is slammed open from idle? How does it effect initial bog off the line? If it matters, my car is a stock Challenger 340, with stock cam and ported stock heads. Thanks.

I know that demonsizzler says that some bogs cannot be tuned away unless the air door is tight against stop. He was right. Aluminum headed 440 with 250* duration, I had it gapped at .040 according to the rebuild and had to readjust mine tight even after tightening the airdoor to get rid of slight secondary hesitation.. Would like more info also.

There is also the choke pull-off. I had to put TWO restrictors in the line on mine to delay the opening.

I have a healthy street 440 with a short gear .... 2.76. But when the secondaires DO come-in ....

Since this was not touched on again Ill take another shot. The timing is about initiation of air\flow into the ventures' which starts the fuel flowing out of the boosters. My theory is by making it tighter (or slower acting with restrictors like Doc F) you are allowing the engine speed to come up more before the air door flops open creating the lean spot or possible over rich spot (??). Where as if you set it up like the factor with .1 to .3 of clearance the door is allowing air to begin flowing which pulls the door open immediately (kinda like a door in the house that is shut wont let air through, but if the door is cracked open a little and another door opens somewhere else in the house the pressure drop and air flow through the house either slams/flings open the door)

The factory setting is to adjust the secondary air door up until it just touches the stop. Then rotate 1.5 turns more on the spring.
Are you guys suggesting not even having the door against the stop in the first place?
I've tried every setting on the secondary door, the metering rods, and drilled out some squirters to .026", .028" and .031". Nothing will cure the bog at the hit of the throttle.
Two different distributors too.
Jetting is good at wide open throttle through a 1/4 mile pass.

The bog is usually the flapper door opening too soon. It snaps open before the carb can start drawing fuel and you get a lean bog. Like suggested higher up in this thread, sometimes you have to make that choke pull-off open slower. Adjusting the tension on the flapper door spring does not have th same affect.

Unless the sec air door spring is a new replacement {NOT} try running the sec to 2 to 2.5 turns this is due to the spring being weaker with age Carefully do this and the bog should be gone if there is no other cause for it. If all else fails get a Mopar Q jet of a 80s truck they work a lot better then most people will admit

It's a new spring with the rebuild kit.
I've tried 1.5 all the way to 3.5 turns in .5 turn increments.
I'm stuck with the Thermoquad for the Pure Stock Muscle Car Drag Race rules, it must be stock.

Check with Scott @ Harm's . . . he rebuilds the TQ and they not only look great, but work great too . . .

I have only ever rebuilt my TQ to factory settings, on factory 360 and 440 cars. Both worked great ! . . . just my two cents worth . . .

Cheers

Mark

Im NOT talking about WINDING the secondary spring door, Im talking about bending the choke pull-off to the air door as shown in this figure.

After establishing about 1.5 -2 turns on the spring tension then bend this rod for this clearance. I think you'll find this is the cure; and only then play with spring tension and door stop to tune the fuel curve and the actuation of the air door.

Ive tried to 0.040 clearance like it says, but on my big cam I have to run it tight against the stop as was suggested by tuners to me.

If you need the complete instructions Ill email my complete pdf of the manual.

Also, this is a great thread on tuning.

https://board.moparts.org/ubbthreads/show...&PHPSESSID=

Here is a short version where I learn the last trick I mentions.

Three things I would be experimenting with on the carb in addition to the initial opening gap and accel pump size size (once you have ignition timing close and you determine the linkage is working right).


1) Richen secondary jetting and set open airdoor angle to stock or a little tigher than stock. If you have blocked manifold heat and are running pump gas you will need to step up secondary jetting as well as primary. I would consider going straight to a .149 sec jet to start with. A wide band A/F meter is really useful here.

2) Choke pull-off orifice size (fill it in with jbweld and drill out in steps, starting with a much smaller than stock size) It may be easier to install a different orifice restriction in the vac hose going to the pulloff. I have seen some manual trans pulloffs with an orifice so small you can barely see it.

3) Air door tension (this is not as critcal as one and two, start with 2 turns and change in steps of .25. I dont think you need to go less than 1.5 turns or more than 2.5)

If you get stuck PM me and maybe we can talk by phone.

Great info guys.
Last night I worked with the choke pulloff adjustments as suggested earlier, but it still had a bog and would occasionally backfire.

Kilroy, I have those instructions but missed the .040" opening adjustment. This makes more sense now. I'll get it pulling in, then make the .040" adjustment from there.

Rapid, I'm already at .101" and .149" jetting. It looks good on the A/F meter and checking the plugs after a run.
I didn't realize there were different orifice sizes on the pull offs, I just grabbed one that pulled vacuum, time to look for ID numbers.

I had to run mine tight against the housing stop, not at .040 as suggested; even at 0.040 I had a bog. I know some are run as loose as .100.

Let me ask you what your carbs 4 digit id #?

Mine is a 6319s, correct for a '73 340 Auto.

Installed a restrictor in the choke pull-off that I drilled to .0135", too small to pull vacuum. Went up to .016". No more bog. The tires spin instantly at the hit of the throttle.
Now a new problem has shown up. As the car gets rolling through first gear, the engine feels as though the carb is either way too rich or way too lean, kind of shuddering. Eventually it gets better after shifting into second. Spark plugs checked good.
I adjusted the amount of opening on the air door but didn't help the higher RPM situation. I'll hook up the Air/Fuel meter to see what's up. Might have to back the jetting off now just to see if it helps.
I'll have to work on it another day.

This is why I love Moparts.

Are you running a stock fuel pump? Check and be sure its good and that your fuel pump ecc is not grooved or going bad seen this on several 340-360s . Also is your intake a egr intake ? that could be partial cause of it acting up in on take off. Another thing to look at do you have a Chrysler Elec ignition? Ran into two control boxes that were bad and acted like carb problem