Quadajet Choke "Heat Stove" Question

[54blackhornet]

Well I am going back to stock QJet on my 71 GMC 350/350. Attempted the Edelbrock/Carter thing with little success. Can anyone tell me if you where able to get the stock 71 heat stove to work properly in cold weather.

Does it help to remove manifold and hot tank to remove carbon build up under cross over passage ?

Thanks

[Crazy]

show me a pic will you

[Mike C]

That damn screw usually broke off for me. I bought a Summit Q-jet with electric choke for my '86 K30 and I bought a JET for my '70 GMC also with electric choke. I was happy with both.

[Coley]

Quick question:
What manifold will you be using? (ie: original-stock or an Edelbrock)
I used the divorced choke on my 72' (stock quadrajet & manifold) with no issues and it worked well....BUT you have to set it up properly and most guys don't unfortunately.
You have to spend some time setting up clearances on the cold start circuit (choke side of the carb) and it takes a bit of tweeking with some small feelers, gauge wires and multiple pliers to do this.
My two bits.
Coley

[JimKshortstep4x4]

I am running the stock Q-jet with the divorced choke on my snow plow and it works good. Coley is right, the choke parts do have to be tweaked to get good results.

Jim

[brown7373]

My 72 with all stock parts starts immediately when I twist the key and works perfectly. The adjustments are important and not difficult.

[praisegeetarman]

Are you running headers? Part of getting the choke to operate as original is the valve located on the outlet of one of the exhaust manifolds. When the engine is cold, that valve closes and forces the exhaust gasses from that side through the center port in the intake manifold (the one that the choke stove is bolted to) and out the other exhaust manifold. Those gasses going through the intake heats up the choke stove faster than it would if you have headers or a gutted exhaust manifold outlet valve. You can still get it to kind of work without the exhaust outlet valve, but the choke will stay on longer than it should. One way to compensate is to bend the rod connecting the stove to the carb linkage so that the choke doesn't go on as far.

Like others have said, if things aren't exactly stock on the motor you have to fiddle with it to get it to work.

[Ironangel]

Not much "fiddling" involved. The procedure is explained in the shop manual, as well as in this video. It's as simple as bending the wire linkage to the correct length. Set the choke with the motor cold. Once you have bent the linkage to the correct length, step on the accelerator to engage the choke. Start the motor and allow it warm up to operating temps, (10-15 min.) Then step on the accelerator (again) to disengage the fast idle. https://www.youtube.com/watch?v=MqArPFwSa7U#t=111

[Coley]

One thing I would do right now while the carb is off the truck is give it a serious 'bench cleaning and set-up' before installation.
Get some carb cleaner and spray it every which way back through orifices, etc and take off the top air horn and clean and recheck your main bowl area in there. Then take some compressed air and fully blow out everything to clean it.
After that I would then follow a lot of the initial set-up instructions on the choke then install it and finish it.
If the carb is in generally good shape you will immediately notice some nice improvements in the way it runs.
My two bits & good luck.
Coley

[54blackhornet]

Stock intake, no exhaust valve on passenger side manifold ? Thanks for the info guys !

[TBONE1964]

Originally Posted by 54blackhornet

Stock intake, no exhaust valve on passenger side manifold ? Thanks for the info guys !

Hey Jack,

I don't believe 72 small block trucks came with a heat riser (valve under the exhaust manifold). You should have a heat stove on the drivers side manifold with the tube from the heat stove to the bottom of the air cleaner.

If you have the intake off, then I would give it a good cleaning. There is a splash shield that you can (carefully) remove and clean the gunk out.

Make sure you have a good choke coil and a good choke pull off. The choke will not work correctly if the choke pull off is bad. After firing up cold, the choke pull of should pull the choke blade open about 1/8 inch or so and run on fast idle until you kick it down.

Make sure you lube up the linkage and fast idle cam with some lube. I use PB blaster for something like that.

Finally, exercise some patients. If your adjustments are off, you will have to wait for the engine to cool to re set them. You could force it cool but it is better to just wait for it. Theses old q jet chokes are also ambient temp sensitive and 10-15 degrees will make all the difference if there is something not adjusted correctly.

I lived in Michigan where you go from 10 to 20's (on average) in the winter to 80 degrees in the summer and everything in between. TBI was a great thing there when it came out in the late 80's

[54blackhornet]

Thanks TBone, I had the carb shop in CA rebuild the QJet, re bushed the throttle shaft, well plugs, float and major clean up and adjustment. They even dynoed it on a 350 before shipping it back to me. I removed the cover off the heat stove to check its movement , put the spring in a pan of water on the kitchen stove, seem to work ok but not really sure it moved as much as it should. Reinstalled the carb, still runs crappy when cold. Does the vacuum controlled air cleaner valve that controls the heat riser on drivers side have a big impact on cold weather start up ? Mine is not connected at the moment....thanks again..

[TBONE1964]

Originally Posted by 54blackhornet

Thanks TBone, I had the carb shop in CA rebuild the QJet, re bushed the throttle shaft, well plugs, float and major clean up and adjustment. They even dynoed it on a 350 before shipping it back to me. I removed the cover off the heat stove to check its movement , put the spring in a pan of water on the kitchen stove, seem to work ok but not really sure it moved as much as it should. Reinstalled the carb, still runs crappy when cold. Does the vacuum controlled air cleaner valve that controls the heat riser on drivers side have a big impact on cold weather start up ? Mine is not connected at the moment....thanks again..

Well, I can't say how much of an impact it will have but it is there for a reason and when it works correctly it will block off fresh air from the air cleaner inlet and allow warm exhaust air to be directed into the air cleaner. You have to also make sure the temp sensor in the air cleaner housing is working. That is what tells the flap when it is warm enough to open and allow the fresh air back in.

Run on the dyno is fine but on your engine, it is a different deal. Is timing set correctly and is your ignition system good? Is there any vacuum leaks on the engine? All of these things will have an effect on cold running performance.

If you have dought's on the choke spring, I would just replace it for the piece of mind. Can you pull the lid of the air cleaner and watch the chke blade open when the engine is running cold? Try and open it just a touch more with your hand or a screw driver and see what happens. You may have to tweak the choke pull off adjustment just a touch.

Hope this helps,
Tom

[Husker]

Mine works fine
Ron

[brown7373]

If you suspect the choke spring is shot, why not replace it? LMC Truck lists one for a 72 for $14.95 42-4636. It says for 1972 V8 4bbl. May also be available other places.

[54blackhornet]

I located a electric choke conversion that eliminates the stock metallic spring for an electric choke that mounts onto the intake. Has any one used this set up..?

[mechanicalman]

Originally Posted by 54blackhornet

Well I am going back to stock QJet on my 71 GMC 350/350. Attempted the Edelbrock/Carter thing with little success. Can anyone tell me if you where able to get the stock 71 heat stove to work properly in cold weather.

Does it help to remove manifold and hot tank to remove carbon build up under cross over passage ?

Thanks

Mine always worked well. If your exhaust cross-over in the intake is plugged or restricted then it would help to clean it out but I know of no method of knowing how to tell before you remove it. I'd probably weigh the pros of replacing it, like "is it leaking oil, coolant, or vacuum?"

You need to tell us a little more detailed description of how it's running cold, does it die, is the cold idle too high or too low, is the choke pull-off working, etc. Set up the hot air inlet tube, if you have not already.

I'd first confirm the choke pull off is working. Collapse the choke pull-off, then put your finger over the vacuum nipple, and see if it springs back or if it only moves a little and stops. If it stops, it does not leak until you remove your finger then and it is usable. If it leaks, replace it and see how it does.

There are 3 adjustments to make and each one affects the other one. Make sure the various parts like fast idle cam and linkages are clean and moving freely, use choke spray to clean if necessary. Do not put oil or grease on them as that will attract dirt and gum it up.

1. Choke pull-off. Bend the linkage rod that goes directly to the pull-off.

2. High idle screw for cold idle speed. Turn the screw.

3. Choke stove coil. You can adjust this by either bending the rod or altering the thickness of the base plate gasket.

If you have a repair kit for this carb, refer to the specs on the choke pull-off to get a rough idea if it needs adjustment.

Then, make sure you set the high idle correct after the choke pull-off. You want it high enough that it does not die out cold.

Then I'd start adjusting the choke coil rod if needed. Start by installing a brand new baseplate gasket that is exactly right for this application. They are usually about .250" thick like this one:
http://www.carburetion.com/Products/...?part=20-2269A
You may have to adjust it several days before you get it where you want it. I recommend to bend it to match the new gasket so that it will always be right if you use the right gasket.

[71K20chevy]

Mine works fine. Aftermarket intake without crossover. Built a bracket that basically holds the coil up to the same height as the original, and it works great.

[davepl]

I am the King of Chokes (or so I claim), so here are a few tips:

1) Choke coil is only used to hold it closed before starting, push against the choke pulloff during warm up, and then slowly open at the right temp.
2) The heat stove, pipe, thermac, and closed element are for driveability when warming up. They prevent bogging and so on. It'd still run with it, as my '63 Imperial did. But you still want them.
3) The choke pulloff is the most important. With the choke closed ANTYHING will pretty much start. Keeping it running and driving from 3 seconds on is up to the air gap created by the pulloff valve and its stop. This is adjusted by bending the stop tang.

In other words, the choke spring has to work, but the adjustments to it are really basic and as long as it can hold the door closed during cranking, that's 80% of its life. Cold stalls and bogs are the choke door. Warmup stalls and bogs could be the spring. Warm over-rich condition could be from the choke spring keeping it closed too long.

To beat this horse further, in the first minute of a cold start the choke spring has pretty much nothing to do but push against the pulloff. Unless it was SO far out of adjustment it couldn't even do that (never seen that) it ain't the choke.

[AlmostClueless]

Hi, everyone,

I'm new to this forum. Actually, it's the only online forum I've ever joined. Anyway, is it too late to join this topic? I know it's years old, but I have a related question. My wife and I just purchased a 1972 Suburban 4 x 4 w/ a 350 engine. It's been sitting for 3 decades outdoors and is really, really rough, but I'm hoping to save it. I can't figure out how to get the heat stove off the driver's side ram's horn. I removed all the screws I can find and it's loose, but still won't come off. It's still fastened somehow, but I can't find what's holding it. I don't want to damage it, b/c I want to reinstall it when (if) I get it going again. Thanks for any help. Take care.

[geezer#99]

Welcome less!
You shoulda started your own thread.
However, post up some pics of what you got.

[AlmostClueless]

Thanks, Geezer! I just now went ahead and started a new thread. I appreciate the help. The old Suburban is out in the middle of our sheep pasture & I don't have any pictures yet, but will try to get some soon. Thanks, again!