Packard Forum Index » Pre-War (1899-1942)

When I bought my '39 Six, I decided one of the first upgrades should be a rebuilt carb as, in the past with other vehicles, a 'new' carb has cured all sorts of ills. I researched the original type on this site and determined the correct unit should be a Carter WA-1. I submitted pictures of the unit that was on the car to the 'carb guys' and they advised it was a Chevy carb off a '56 Bel Air. I was given the option of automatic or standard choke and opted for the standard version. My woes with trying to get this car to run have been well documented on this site and I decided to procure yet another rebuilt carb to see if possibly, the first one was in some way, deficient. The carb store told me to go with the automatic choke version as that is what came with the car originally and the standard choke unit was a 'generic' Carter carb that had different porting and jets than the 'original' carb????? This makes no sense to me, but my 'carb smarts' are quite limited so I just 'did what they said'.

My question is this: there is a male threaded port coming off the auto-choke 'element housing' and I have no idea what should hook up to it. The Chevy carb was auto-choke and there were no fittings and the first rebuild manual choke had a sleeve cable (that I installed) and now this version has this, about 1/4" NPT fine thread, on the bottom of the choke housing. If anybody could send me a picture of the proper hookup procedure, I would be most grateful. Many thanks in advance.

Hi Newbie,
Until the real experts can weigh in, I believe you are looking at the hook up for a heat tube from the exhaust manifold. Perhaps a site search in this area will find some pictures.

Best of luck

Mark

Is there an opening in the top of the exhaust manifold a short distance in front or back of the port on the carb choke housing? If so that is the choke stove and where a piece of steel or copper tubing connecting to the choke housing lands. Generally the end of the steel or copper tube is just pushed in as a snug fit in the choke stove tube. Some manifolds have a square plate covering a box like chamber cast into the manifold which works as the stove. Believe the tubing screws onto a fitting in the plate with that arrangement.

The tube type stove consists of a steel tube which is pressed in holes in the manifold and has an opening on the bottom which lets some air in. The steel tube just passes thru the manifold and at no point is the exhaust gas and the air in the stove tube able to mix. The chamber type uses the same principle except the manifold casting acts as the stove and metered air is admitted thru a small hole the chamber cover plate. Vacuum from the choke system draws air from the stove which has been heated by the exhaust gas in the manifold so it can work the bimetal element in the choke mechanism. As the element heats it relaxes so the choke can open. When the choke opens the vacuum is reduced so there is just a minimal amount of heated air present to keep the element relaxed.

There is a photo of a six engine in the 39 archive which may show the tube. Since the photo is not the best and is taken from a distance I can't really tell for sure if it is the tube or linkage so won't post unless no one else has anything better.

Thanks Mark and Howard for the replies.... I did look at the exhaust manifold before I posted the query but will have to look again. Initially, I did not see anything obvious on or about the exhaust casting that suggested itself to the purpose of heat pick-up. A picture would REALLY help if someone would humor me. I read your send several times Howard and from what I can gather, there are TWO methods of picking up the heat from the manifold - one where a tube is heated on the surface of the manifold and one that actually passes through the casting???? Am I interpreting this correctly?? I am thinking if this is the original engine (which I believe it is, based on the numbers comparison I did when I bought the car) and the original carb was an auto-choke - then the manifold SHOULD have some provision for this heat hook-up. I am stymied to not be able to easily find it. Like I say, a picture would be worth a thousand words!!!!

This is the best I can come up with for now. Hopefully someone with a 39 will see your post and take a detailed photo for you.

The first illustration is from the 39 fact book but it doesn't identify if the engine is a six or eight or which carb. With the hump in manifold I think it might be an eight.

The photo is from the archive and identifies as a 39 six but the angle and distance in the photo is such I cannot tell if the straight piece is a tube or linkage. It does appear to be connected in the area of the choke housing where the threaded port is as is illustrated in the WA-1 rebuild information.

The opening for the stove appears to be on the side of the manifold in the fact book illustration and if that is a tube in the photo, curving into the side of the manifold on the six. Both stoves may be the chamber type.

The third item is a postwar manifold illustration showing the typical construction of the tube thru manifold type stove.

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Thanks a lot Howard - I am going to work on the car this morning and will get a mirror in there and see what I can see. You're right, that one photo is definitely a '39 Six, but it is hard to tell where the tube actually goes. Any suggestions on the minimum size of the heat tube?? Would 1/4" be too small??
Will report back tonight after I spend the day on it.
Chris

I believe it is 1/4" on most all chokes. Factory used steel tubing but copper or cupronickel is so much easier to work with.

Thanks Howard.... yeah, I was definitely going with copper; so much easier to bend! I have access to a small-tube bender but after the hours spent trying to remake the gas pick-up tube for the gas tank out of steel tubing, and eventually opting for copper - I have learned my lesson!!! Chris.

The original carburetor for your 1939 six would have been a Chandler Groves.
I'm not sure about 1939, but for 1937 there was a small passage in the base of the throttle body that drew warm air from a matching passage in the manifold.
See attached photos of the 1937 setup.

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basic rectangular choke stove. Auto parts store used to sell them for $5bucks or so. straps to exhaust manifold, tube goes inside / tube to carb choke. that's all it is. I'll try to find a picture...

DAF