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1930 Buick Series 40 Carb Heat


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As some of you have may read, I've been having trouble with a severe vacuum leak around the heat tube in the carb. heat assembly on my 1930 Buick. I removed the unit and could not really find where the leak was. I brought the unit to a machine shop for him to inspect. We ended up removing the heat tube altogether and he machined a plug to block off the port that would have been hooked to the pipe that went to the exhaust valve at the front. (the entire valve is missing on my car). I was aware that the heat tube in my car had been replaced with a rather thick one and had been somewhat restricting the flow of the air/fuel mixture. Well let me tell you, taking out that tube was like putting a turbo on the engine! Wow, what a difference. I made sure the back plate was well sealed and there are no vacuum leaks now with a very wide throat for the air-fuel mixture to travel through. Big difference on the interstate. With the high speed rear end gear I have in the car, it travels easily at 55 mph now. It is capable of much faster speeds , but it is a bit scary driving that car much faster than 55. Oh, also, the engine is much quieter on the highway. There isn't nearly the loud hissing sound from the carburetor that I used to hear. I imagine my fuel economy went from 8 mpg to 2 mpg now, but the car sure runs better. I thought I would let the group know in case anyone else would want to do the same to their car provided they've already disabled the heat system as I had already done.

Please let me know if you think there are any pitfalls to what I have done. So far, I don't see any ill effects.

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Michael,

I did the same thing to my 1931-57 Buick by using Freeze plugs. They easily press into the openings on the heat riser and exhaust valve without any special machining. Works great!

BCA members who went to Rochester may have seen a lot of work going on under the hood of a 25 Buick Truck on the front lawn of the convention center. Part of the job was to replace the inner heat riser tube that was severely rusted and passing exhaust into the intake. With help from the local Midas Muffler shop, who cut some standard exhaust pipe and pressed it into the heat riser body for only $25, we got it running in time for the BCA PWD dinner on Friday night. This kept it original and solved the same problem.

Mark Shaw

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Well mine was missing the front exhaust valve when I got the car. After talking to many people, the consensus is that I should keep the carburetor heat disabled. So, with the heat disabled, I don't need that heat tube, right?

however I may be suffering from a bit of some consequences of removing the tube. I can't get the carb adusted right. If I adujust it to run right at driving speed, it idles way too richly. If I adjust the carburetor so that it idles ok, it's way too lean at driving speed. I have to pull the choke out half way to get it to run right. Any thoughts on that? Is the venturi too big for this carburetor now? Or could there be another problem?

When I got the car 4 years ago it would barely run. I sent the carburetor to the "old carb doc" and he resotred it completely. After that it basically ran like a stuck pig.....well an old stuck pig. So, I don't think there would be much wrong with the carburetor as it has been completely serviced.......

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Sounds like you still have a vacuum leak. My 29 Buick had the same symptoms & I ran for over a year with the choke part way open to make it smooth out.

I discovered that since I had removed the vacuum wiper motor, the disconnected tubing created a significant vacuum leak. I plugged the tube at the top of the windshield, and it solved the problem. (I still need to fix that wiper motor.)

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Mark,

Yeah, I'm sure my wiper motor is shot. I'll send that off for repair this winter. However, it hasn't been hooked up for years. The vacuum line has been pinched closed and there is no leak there. That also makes it hard to hook up a vacuum gauge. I'll have to use a tubing cutter to cut the line and then I will hook up a small piece of hose to it. I'll be able to clamp the hose off and remove it to use a vacuum gauge. I haven't been able to find any other leaks. Spraying WD40 around the intake gaskets show no leaks. So, I think maybe I need to play with the carburetor adjustment some more. The over-rich problem at idle is likely due to a stiking or non working float.

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Check your high speed jet for cracks. This too is a common problem with old brass parts. Just remove it, plug one end and put some pressure on it with air or water to find any leaks. I little solder on the outside will seal it again if you find a crack.

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