Converting divorced choke to manual choke

[skokie]

How would you convert a divorced choke setup to a manual choke setup?

Thanks

[spencra]

I'm kinda curious myself.

[jimfulco]

Do they still sell choke cable kits with all the different brackets & connectors? Used to cost ~$5, but that was a while back.

[Palf70Step]

Yes they do. I got mine at Autozone or Advanced Auto (forgot which). Find a place and mount the pull knob, run the cable and hook er up. pretty easy. Toughest part I had was finding a decent mounting point close to the carb that permitted enough movement for the choke, but not aloow the cable to flex and bend. I have it disconnected right now because the rest of the truck is , but they are pretty simple. They even come with directions, which I know is sometimes an evil thing to think that we would actually look at those directions.

[68speedalert]

Coming from a guy who used to TRY to install them professionally.....don't convert. As mentioned, you won't find a good spot to mount the bracket, the universal kits are made too weak, etc. If you're not careful, you'll bend some of the linkage on the choke when trying to set it.

What's the prob with the divorced choke? You're better off in the long run to repair it, unless you like to constantly be jacking with the conversion.

Many guys say they had trucks with factory manual chokes that work great. They do. The carbs are different and the brackets don't bend.

HTH

[skokie]

Thanks for the info. Let me ask this. Is is possible to change the convert the carb to a manual choke setup?

[68speedalert]

Are you converting a Qjet on a V-8?

[skokie]

Originally Posted by 68speedalert

Are you converting a Qjet on a V-8?

Yes.

[68speedalert]

I have never seen a factory manual choke set up for that carb. Maybe guys with heavy truck experience might be able to help, but I think most of those had 2bbl.

Sorry for the bad news. Again, what's wrong with the auto choke now?

[ddsmith]

I had a divorced choke on my 71 Vette with a 454 and a holley spread bore carb that was converted to a manual choke. It worked fine but during the engine rebuild I decided to make the divorced choke work correctly and it works just like it should now. Some of the things that are not particularly great about the divorced choke is the heat riser valve. Most people take them out or wire them open. This prevents most of the exhaust gas from running through the intake manifold during cold start up which was what the heat riser valve was suppose to accomplish. It would shut when cool and drive the drivers side cylinder exhaust through the intake manifold center port and out the passenger side exhaust pipe. This in turn heated the carb up and the divorced choke heat stove. When the temp of the heat riser caused the valve to open then normal exhaust was restored. Most people also block the center port on the intake to prevent this hot gas flow. Usually with a gasket set which blocks the flow. This can lead to low temperature hesitation because the carb/intake is cold enough that the atomized fuel repuddles on the floor of the intake manifold. It's sort of funny. We what fuel warm for atomization purposes but we want air charge cool to pack more air into the cylinders. If the fuel heats up to much it can cause vapor lock situation or percolation of the fuel out of the fuel bowls causing to lean or to rich a mixture. Boy that fuel injection looks better and better the more you think about it. Good luck, hope all works out for you.
Just a P.S. the manual cable was hooked up at the top linkage to the choke plate originally. This created no real resistance for the cable which is good because as someone said the cable kits are usually cheap and mounting brackets are too.

[skokie]

Hmm maybe you are right. I looked through the repair manual and assembly manual and I dont see anything. Let me ask this. If you had a 327 in 68 with the divorced choke would you have a choke delete on the dash?

[68speedalert]

Choke delete? Not sure what you mean. You mean there isn't a place for the choke cable in the dash?

Good post ddsmith! Very few mechanics, much less owners, know how the system works. I would add that 72 trucks do NOT use a heat riser. Instead they have a alight restrictor on the right manifold, at the donut gasket. My exhaust man (who was a '72 owner himself) swears he leaves out the restrictor without a problem.

[skokie]

Ok I found this out. The manual choke was for a 307 with a 2 barrel. 327 had the qjet with divorced choke. So that means my truck had the 307 not the 327 from the factory.

[68w/sbc406]

Originally Posted by skokie

Ok I found this out. The manual choke was for a 307 with a 2 barrel. 327 had the qjet with divorced choke. So that means my truck had the 307 not the 327 from the factory.

or your dash was swapped out and you have the dash out of a choke truck

[68speedalert]

Thant's correct. My 68 origionaly had the 307 with the 2bbl and manual choke.

[avejoe]

Pardon my ignorance...

What is "choke"? I know it's a little lever on most gas engines, but what is it techically?

What is a "divorced choke"? Is it what you do when you're real mad at your ex? Seriously, what is it?

What is the technical purpose of the heat riser between the exhaust manifold and the exhaust pipe?

What is the purpose of the stove pipe between the driver's exhaust manifold and the air cleaner?

Thanks in advance for making me more smarter.

[poff]

The choke is a flap that restricts the air flow in to the carb. to help cold starts.

A divorced choke is a bimetal spring mounted on the intake manifold. There is a port under the intake that lets coolant or exhuast (can't remember which) heat up the spring to operate the choke.

Describe the heat riser.

The stove pipe (in theory) diverts hot air that passes by the exhaust manifold into the air cleaner to speed up the warm up process. A properly operating system has a vacuum operated heat valve that diverts back to cold air once the air cleaner warms up.

A properly working and adjusted divorced choke should work fine. The only problem I had with mine is the spring went bad once. It would be better to convert to an electric choke carb.

[67ChevyRedneck]

I used an adapter and installed a 650 edelbrock with an electric choke. Works great, super easy to install. Just a suggestion.

[ddsmith]

The big problem with electric chokes is the way they function. Most of the electric chokes are designed to open in a relatively short time. I believe that they assume that the hot air will be arriving to the carb and choking to increase the air/fuel mixture will no longer be necessary. If you think about how all this stuff was designed to work together it makes sense. But you know how us mechanically inclined people are. We figure I don't want any stinking warm air going to my carb that will kill performance. The answer is yes and no. Actually on cold startups it help performance so to speak because it allows the carb to get closer to the normal air/fuel mixture sooner by providing heat to help atomized fuel. That is also the purpose of the heat riser valve driving exhaust through the intake manifold. Those cast iron manifolds take a while to heat up without help. That prevents atomized fuel from repooling on the intake manifold floor. So hot air and a quickly warmed intake manifold help during cold conditions.
Now for the hurts performance. The heat stove which goes to the air cleaner is usually the first thing that is tossed along with the air cleaner housing. It doesn't look that nice. The problem is that you normally lose the hot air supply. If you leave the original stuff in place the only way that having it hooked up will hurt you is if the little thermostatic switch in the air cleaner housing messes up allowing only the warm air into your engine. This does not normally happen. The job of this little valve is to sense temp in the air cleaner housing and modulate the door in the snorkel and provide the correct temperature air. This is really not a bad system from what I've learned. The problem is that the heat stoves don't last in that environment very long. So usually you'll see that the snorkel port which should go to the heat stove goes nowhere. Basically the valve does no good because in either direction it is getting engine bay air. Some argument can be made that the stock air cleaners are restrictive and hurt performance. I'll have to agree but it's a trade off to go to an open air element. This is particularly true for someone who runs their truck in cold regions of the country. As for the heat riser, if it sticks you bet it kills performance because your exhaust temps are pretty high and they are heating the floor of the intake manifold and in turn heating the air/fuel mixture way up. Less charge to the cylinder equal poor performance. With the heat riser functioning properly I believe it still lessen your cars performance because it is a path to heat which doesn't have any valves to stop it. There isn't really any flow because the exhaust will take the path of least resistance which is out the tail pipe. Sorry if I'm boring you all with this but I found it interesting at one time and studied it for a while and thought I would share with the group.

[68speedalert]

Again ddsmith, an excellent post.

Electric chokes, especially factory ones, work very well. A lot of F*rd carbs have both electric and hot air coming into them. Below about 50 degrees, they warm off of the hot air, above, they operate on the electric side.

I have found that the GM electric chokes work very well. The easiest conversion for our trucks IMO is to find a qjet from an 81-86 305 GM truck. I am partial to the qjets, sorry holley & carter.

The 70's qjets generally flow more cfms but don't come with an electric choke. You can convert them. If anyone want's detailed inst. how to convert one and not have ANY problems in cold weather, let me know, it's a little involved to do if no one cares.

There are some models made in the 60s, 70s, and 80s that flat would NOT run in cool weather if the heat riser and/or air cleaner heat sove didn't work as designed. Thses items really don't have a big affect on our trucks, at least here in mid-MO.

One other function of the hot air snorkel was to prevent carb icing. This happens in cold weather with extremely high humidity. Air cools as it goes past the throttle plates. When the planets are aligned just right, (around here anyways), the moisture would condense on the plates and actually form an snowball. Your vehicle will not idle. If you shut it of for awhile, the heat from the engine would rise and melt it and the engine would idle until it happened again. The hot air stove kept this from happening.

[Greg R..]

i have looked all over the place and can't find a divorced choke for my inline 6 250 1969

[HO455]

I ran one like this years ago and it worked great for at least eight years. Mike's may also have the divorced choke for your I-250 you need.

http://www.carburetor-parts.com/Divo...on_p_3220.html

Photo.
http://67-72chevytrucks.com/vboard/a...1&d=1416146965