Hi all, I have a 61 LeSabre with a Rochester two barrel. The previous owner put an electronic choke on. Cheap POS and wired it to the coil. Not sure what he was thinking???? Anyway, I want to put is back to stock. For the life of me I cannot figure out where the heat tube connects to the manifold or exhaust manifold???? Any help would be much appreciated. I also need the stock choke parts and heat tube, any good supplier suggestions? thanks, Kensey Pittsburgh
on the manifold, there is a small nipple that the heat tube attaches to. or you can buy a choke stove that attaches on a convenient place on the manifold. (it's what I did...)
I don't think my manifold has the nipple. So some have it, some don't? Is that right, seems weird. I'll check again tonight, but I swear it's not there. What would have been the stock set up on a car with no nipple? thanks, Kensey
From the service manual, under the section pertaining to the 2-barrel Rochester carb: g. Operation of Choice System The choke system is composed of a thermostatic coil, vacuum choke piston, offset chokevalve, fast idle cam and choke linkage. Itsoperation is controlled by a combination ofintake manifold vacuum, the offset choke valve,atmospheric temperature and exhaust manifoldheat. See Figure 3-22. The choke thermostatic coil is calibrated to hold the choke valve closed when the engine is cold. When the engine is started, air velocity against the offset choke valve causes the valve to open slightly against the torque of the thermostatic coil. In addition, intake manifold vacuum applied to the choke piston through the vacuum passage tends to open the choke valve.Vacuum pull on the choke piston is offset by the tension of the thermostatic coil. As the engine warms up, heated air is drawn into the choke housing through the choke heat tube through a passage in the choke housing. As the engine temperature increases, it causes the thermostatic coil to relax its tension, which together with vacuum pull on the choke piston and air flow against the offset choke valve causes the choke valve to open gradually until the engine is thoroughly warmed up, at which point the choke valve is fully opened. A mechanical choke unloader is incorporated to open the choke valve slightly when the engine is cold. The choke unloader provides a means for opening the choke valve to correct any loading condition encountered during cold starting. To prevent stalling during the warm-up period, it is necessary to run the engine at a slightly higher idle speed than for a warm engine.This is accomplished by steps on the fast idle cam. The fast idle cam is in turn linked to the choke valve shaft by the choke rod, choke trip lever and choke lever and collar assembly.This holds the throttle valves open sufficiently during the warm-up period to give increased idle RPM until the choke valve moves to the fully open position and the engine is thoroughly warmed up. When I get out to the garage today I will snap a few pictures of mine. Even though it is a Stromberg, the nipple on the exhaust manifold should be the same I would think.
Okay, here are 3 pictures of the tube and a close up of the nipple area. I've moved my tube out of the way so you can see the actual nipple. You can see where it is in relationship to the oil dipstick. That should give you a good place to look. By the way, I need a new tube for mine or at least a better way for it to connect at the manifold. It has rusted off over the years and now I just kind of stick it in there. HTH
Mosslack, Thanks a lot!!!!! This really helps. I'll look when I get home, but I swear i'm nipple-less. Ha! thanks, Kensey
I have 2 of the tubes, NOS. They were sold without the insulation. Would sell for $42 each, shipped to US48 address. John
Hey John, how is the connection made at the nipple? Does the tube just stick into the nipple or is there more to it? I'm thinking mine may be broken off inside the nipple itself so that would need to be fixed first.
The tube is just an interference fit to the nipple. It's 1/4" OD. The end of the old tube is probably rusted off in nipple as you suspect. I've used copper tubing as a replacement when originality didn't matter. John
That is what I thought. I can probably use a drill bit to clean it out. I was planning to see if I could find a steel tube that diameter and use my tube bender to shape it. I believe it's just a flared fitting on the end which connects to the carb. Thanks!
Yes, even steel brake line will work and is easy to bend. The fitting at the carb is a ferrule/nut combo that can be purchased from a hardware store.... look in the plumbing section.
The Rochesters may use a ferrule/nut compression type fitting, but the one of my Stromberg is flared as you can see in the picture below. Next question, how far does the tube slid into the nipple? I want to make sure I get all of the old tube out.
This looks to be a good solution. http://www.oreillyauto.com/site/c/d...6_1748&keyword=brake+lines+(steel)+-+domestic I think a couple of feet would do it, but at only 89 cents a foot might as well get a extra foot. Flare the carb end and slide my insulation over it and presto, new choke tube! :beer
Do bear in mind that there has to be an air intake for the exhaust manifold heat tube. Some of the older cars have a second tube that runs back to the air cleaner to provide filtered air to the choke. Some cars just have a tube pressed into the exhaust manifold with the bottom open. Be sure that when suction is applied to the choke tube opening in the exhaust manifold, that there is air flow. If not, the entire project will be a waste of time.
Okay, I just drilled mine out. Had to remove the generator and use an extension with the drill bit to get the right angle, but it is clear now the entire length of the nipple, about 5/8 of an inch or so. Where does the air come in from on this one? It only has the single tube running up to the Stromberg 2 barrel carb. FYI, I was able to use my original tube, just had to re-bend it a bit. I started the car and the choke seems to work right. Loads up a bit at cold start, but clears up as it should after running a few minutes. Now I need to drill out the threads on the generator adjustment hole as it stripped when I put it back onto it's mount. Always something!ou:
So I decided to put a manual choke on the Rochester 2bbl on my 61 today. Got it hooked up and working good. Stock air cleaner won't fit. WTF... Crossroads: Switch back to the stock set up, which I don't have the stock chock spring and side cover. Had a ****ty electronic one on it. OR, switch to an aftermarket air cleaner. Don't they have better air flow anyways? (Good justification right????) What is a good way to close off the exhaust manifold nipple? Thoughts?
There's no need to close off the hole. The other side of the hole is open to the atmosphere. Exhaust does not flow through it.
Really? Now I'm a bit confused. I thought the nipple went through to the inside if the exhaust manifold. So exhaust does not flow through the heat tube to the carb spring? Is it just heat then?? Someone please explain this to me, totally confused... thanks
