Update On KJ's Carb

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secondarys CLOSED unless you got your foot in it. (i think)Remove the screw. :) The other is the choke pull off, it should open the choke just a little after it starts, so it wont flood the engine. there are two idle screws on a q-jet, left and right on the front lower part of the carb. They might even have plugs in the holes so you cant mess with them. I have only seen them with flat slot type screws.

Okay...

Careful you don't drop any parts down under the porch. ;-(

Choke pull-off(s) *or* vacuum break(s)

Secondary air door.

This serves as a dampener to control secondary air door opening at WOT, prevents bogging from having the secondaries open too quickly. Often times, there is also an adjustment screw as part of the front choke pull-off which is also a choke adjustment, the screw moves a lever that hangs down and acts upon the choke linkage (the green colored thing), so there are actually two different adjustments that need to be made when dealing with this device. GM had many versions of choke control on their carburetors, so everything I say here is a generalization since I can't actually see what your set up is.

Two speed adjustment screws on a Q-jet. The one on the drivers side (left) is the curb idle adjustment and is meant to only be adjusted once the engine is fully warmed up and the choke fully open. The one on the passenger side (right) hidden *below* the front choke pull-off is the fast idle adjustment, it is adjusted to the manufacturers specification usually on the second step of the fast idle cam.

No. Adjusting the rear choke pull-off is done either by bending the linkage rod or by an adjustment screw (allen head) in the end of the choke pull-off diaphram housing. This allen head screw MAY have an anti-tamper cover on it, they did things like that back in the 80s. Initially, the choke pull-off should pull the choke plate open about 25-27 degrees (this requires a special angle gauge to do properly)

Any good Chiltons, Motors manual or instruction sheet from a rebuild kit will have the proper choke adjustment instructions in the proper steps (important), you'd be well advised to search such out. Q-jets usually used staged chokes, meaning that the two choke pull-offs opened the choke valve in a sequence once the engine started running, the rear choke pull-off often either had a delay device or its vacuum supply was routed thru a temperature switch that was usually mounted in the air cleaner housing.

FWIW, current to heat the choke thermostat (it's fully electrical) runs through an oil pressure switch, this oil pressure switch will be located either next to the distributor screwed into the block *or* above the oil filter. It will be either a two of three wire/terminal switch and is very likely the reason (as an earlier post described) why your choke isn't opening as the engine warms up. The factory time spec is 3 minutes, meaning that once the engine is running, the choke stat should allow the choke to fully open in three minutes. if this oil pressure switch is missing, inoperative or disconnected, you will still measure

12 volts at the choke stat electrical connector because voltage from the choke warning light is seeking a ground thru the choke stat, but there is not enough current to make the heat necessary to open the choke stat dueto the resistance of the choke warning lamp bulb. (surprised no one else mentioned this)

I live with my parents, if it was my kitchen I would have done it in there but I KNOW I'd hear about it for a week or so while the gasoline smell subsided.

There is a weird lobe on the back of the diaphram that might cover it. However my machine screw method seems alot less perminant than bending (I thought of that, but I like to try to be able to undo things I know little about)

Would that come with a rebuild kit? Why can't a normal angle-measurment tool be used? Just what is it measured in relation too?

It's a good thing to know this, but I believe that you are wrong. My o.p. gauge is still working. Thank you for the local of the switch though. You wouldn't happen to know how to read the frikken thing would you? Mine goes to 60psi on start up, and drops just below the line between 30psi and 60psi. I'm guessing this is like 43-45psi? (also, that seems high?)

Don't much like the gauges (not as much as I thought I would) - steering wheel is usually in the way and there not as accurate as I would like. Does it have any kind of a dummy light for engine temp as well? Or do I have to keep an eye on the temp?

-The Lonely Grease Monkey

1985' 305CUI TH700R4 NP203 K5 KJ's successor

"Ignorance is preferable to error; and he is less remote from the truth who believes nothing, then he who believes what is a wrong." - Thomas Jefferson

The anti-tamper cover is a tin cup that is sorta staked in place, not unlike the anti-tamper covers that used to be put over idle mixture screws on carbs in the 70, i.e., it spins in place over the screw boss in the choke pull-off.

Nope.

The tool is just a protractor device, anything you can rig up will probably work. See:

#372 It sticks to the (closed) choke plate with a magnet, the scale is set to zero, the bubble vial is centered, the scale is then set to the degree spec, the choke pull-off is striked via applying vacuum, the choke is then adjusted so that the bubble vial is centered.

The choke plate being fully closed.

Well, I'm looking right at the wiring diagram for your truck, so it's unlikely that I'm wrong. Not to mention that it all is the way I recall it being back then when I was working in a Chevy dealership.

That's because the *sending unit* for your OP gauge is a totally separate component from the OP *switch* that controls current to the choke.

Sounds about right.

SB Chevy oil pressure relief valves are set to 45PSI, cold (thick) oil can't be bled off as easily as warm thin oil, IOWs all normal.

I don't think there are any warning lights, but that doesn't mean you couldn't add your own.

So brute force is going to be reqired?

/me pulls out 6' crow bar

I was just a' hopein'....

I'd make it work. Think it was scribb who said I'm a resourcefull prick (and cheap)

I was trying to think today how I could roll my own. Lost in meandering thought of ridiculously complex wiring diagrams and photo diodes and forest m mimms, I almost ran off the road.... Still didn't figure it out. But if someone here could enlighten KJ, I think I'd put the idiot switch on the electric temp sensor and install a nice ether temp gauge I have. ($19.99 at Wal*mart for ammeter, op. and temp)

You regulars might remember ol' KJ killing his 88' S10's ECM with a misfortunate fire-wall drilling accident....

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===============Update=========== The idle screws I discribed are for idle MIXTURE not speed. Also,be aware that you should not have to adjust the crap out of everything/anything on the carb like the choke pull off angle. If you find yourself having to do this you are most likely trying to cover up another problem. ( assuming of course someone didn't already screw it up) :)

No, finesse. Either a die grinder or a whizzer wheel to cut thru the barbs that hold the cap in place. Brute force will only destroy the piece. See:

some examples of various choke pull-offs.The first three are primary pull-offs, the fourth one, part# 53107293 is a secondary pull-off, notice the projection to the left, that is where the allen head set screw *might* reside and where there *might* be an anti-tamper cover.(if this is the style you have which I don't know because I can't see it)

Nuh-uh.... [snip]

The factory repair manuals from back then had a degree to decimal conversion chart, this allowed converting from the degree spec to a plug gauge (not sparkplug), the plug gauge could be used to set the gap between the upper edge of the choke plate and the air-horn wall once the choke pull-off was stroked in by applying vacuum to it.

[snip]

You can install an oil pressure switch by "T"ing it in with any of the other OP switches or senders, it is then a simple series circuit from 12 volts >a bulb >new OP switch which completes the path to ground when oil presure goes too low. Same deal for a temperature warning switch, find an un-used pipe fitting in the intake or cylinder head, install the new temperature switch and wire a simple series circuit as described for the OP warning light.

As it came from the factory, the choke warning light also served as a low oil pressure warning light since the switch that controls current to the choke stat would open circuit when oil pressure dropped (turning on the choke light), so it is in your best interest to learn how the circuit (choke heater) works, fix it correctly and not do a hack job as others may have suggested, kill two birds and all that.

Hu-boy....