1929 DeSoto Plugs Bubbling

[seando]

Hi All, I am working on a 1929 DeSoto flat 6. I am having an issue where there appears to be gas bubbling out from the spark plugs. The car will start and idle (rough) with good plugs.

 

I kept cleaning the plugs and it would run for a while then foul the plugs. Got new plugs (AutoZone) and the bubbling is a bit more exaggerated. I've rebuilt the carb several times and adjusted the float. After a failed start (because of fouled plugs) she does piss gas out the bottom of the carb. Most likely gas that is being sucked up, not burning, and falling back down. (I have noted the recycle system posted by carbking elsewhere). Have done a compression test and all cylinders are within range (60 - 70 pounds each, warm). 

 

Here is the rub; the carb is a Zenith 7066C. No rebuild kits exist and as best we can tell it is a tractor carb. Been talking to Mike's Carbs about it. The rebuilds I have been doing consist of cutting new gaskets, washers and cleaning all pieces. Things like plunger are a best effort.

 

I know this is kind of an off the wall one, but these barn finds are full of ghosts of restorations past. Am I looking at buying a new carter bb1 carb or are there any other suggestions? 

 

And if I am pushed to a new carb, does anyone know the exact one for the 1929 DeSotos? 

 

Thanks all. This is the final piece before I drive her down the road again. 

[Rusty_OToole]

First of all it's a flathead six not a flat six. Subarus  Porsches and Corvairs have a flat six, doubt yours is one of those.

 

Bubbling around the spark plugs indicates gas leaking past the plug gaskets. Either the plug is not tightened or the seating area is damaged or maybe dirty. Be sure this area is clean and tighten the plugs properly.

 

With new plugs tighten  until gasket meets the head, then another 1/2 to 3/4 turn. Otherwise, 25 to 30 ft lbs.

[carbking]

There are a couple of misconceptions with your post, but first:

 

The original carb for a 1929 DeSoto was a Stromberg type U-1 Stromberg number A-12181, DeSoto number 44125. This was a die-cast (zinc alloy) carburetor made from a zinc alloy that had about 4 times more lead than modern zinc alloy in the mixture. According to a metallurgist I contacted a number of years ago, the impurities in the lead is the cause of the swelling and subsequent cracking and breakage of this early zinc alloy. There are probably no useable original Stromberg type U-1 carbs in our solar system. Of course, one can use "lost wax" to cast new castings to replace the originals for a numbers-matching show-car, but the process is not inexpensive.

 

So one has the option of spending a bunch of money to recreate a Stromberg U-1 (which was an excellent design in its day, just a poor choice of materials) or purchase a replacement carburetor of some description.

 

Now to the misconceptions:

 

(1) The Zenith number 7066C is not a tractor carburetor. It was an excellent replacement carburetor produced in the 1940's for smaller automobile engines.

(2) Carburetor rebuilding kits ARE available, by special order. The rebuilding kits consist of new fuel valve and gaskets which are custom-fabricated for the carburetor.

(3) And Rusty has already addressed the fact that the carburetor is not causing fuel bubbling around the spark plugs.

 

My professional opinion would be to rebuild the carburetor you have; no need to buy a new (or different) carburetor.

 

Jon.

Edited February 19, 2018 by carbking (see edit history)

[old car fan]

Did 29 still have a vacuum tank

[old car fan]

Really glad carb king chimed in,I think my friends is a 28 roadster ,I rebuilt his tank,runs fine. ,listen to carb king,.

Edited February 20, 2018 by old car fan (see edit history)

[richasco]

The '29s did use a vacuum tank. There shouldn't be anything leaking past the plugs. Check the plug gaskets and sealing area.

[seando]

Y'all are quick to reply. Thank you! 

If I can get a rebuild kit that's what I'll do. I will call The Carburetor Shop Tuesday and order from CarbKing if I can. 

It does have the Vac fuel pump / tank. I did rebuild and recork that and it does suck as I hoped. Gravity feeds to the carb bowl.

Will also re-check the seal from plug to head. With the plugs fouling again and again does that indicate I am passing too much gas up from the carb?

[Bill Harmatuk]

My 1930 Chrysler CJ, had that same, all cast iron carburetor Zenith on it when I bought it. No vacuum tank. Has a fuel pump.

It only ran with the choke half closed. Could never get it to work right. 

I came across a BB-1 really cheap off a 1930 CJ that was being rodded and boxed my Zenith up.

I plan to have it rebuilt one day so I can run my original air cleaner.

If I were you I would have that cast Iron Zenith rebuilt. Probably a better carburetor. 

They put BB-1s on everything. They are good, and you can buy rebuild kits for them, but they made big and small jetted models. Its a crap shoot unless you do some research.

 

Good Luck

Bill H

[hchris]

Fouled plugs are usually a good indicator of over rich mixture, black and sooty is the indication, wet and oily will indicate oil leakage. As others have said bubbling at the plugs suggests wrong plugs, lack of plug gaskets, not enough plug torque.

 

As to over rich mixture, assuming the choke isn't stuck closed, I would be looking at :

incorrect mixture screw adjustment

worn float valve needle or seat

wrong float height / sinking float.

 

 

[seando]

Update: Talked to the carbking and ordered a custom made rebuild kit. YEAH! Also got some invaluable information from him. And wrenched down the plugs tighter than I ever have before. No bubbles. 

 

Have taken to adjusting the carb, pre-rebuild with the kit and had to back out the balancer 2 full turns to get her to run leaner. She runs, for now, pretty darn sweet. I even took her out on a road test today to the bus stop to pick up the tax deductions. Contrary to the video the vac fuel pump is apparently not working properly since I ran out of gas on the ride home. I know that it has worked since I re-corked it because I have to fill up the tank. Maybe it isn't keep up with the driving car but does when it idles in the garage, i am not sure. I may splice the line under the car and insert a 6v electric fuel pump w/ gauge in-line even if it's just as a backup. 

 

Little by little. 

 

youtube.com/edit?o=U&video_id=eWRF_QzTcxA 

[jrbartlett]

Put in some time to learn how the vacuum tank works, and make sure yours is up to snuff. Vacuum tanks are generally less troublesome to live with than electric fuel pumps -- they don't make noise, they don't require electricity, and they don't overwhelm the carburetor like a fuel pump can. There are people who rebuild vacuum tanks. One of the things to check for is a loose brass bushing/valve seat at the top of the tank. It can cause flooding at times -- then it can bounce back into place and the car will run fine until it falls out again. Carbking is a good source of info on vacuum tanks as well. If your tank is Stewart Warner, there is a wealth of reference information (even YouTube videos) available via a computer search. 

[old car fan]

Agree,But as well ,there should be not that much fuel,around the plugs.I know the common problems found,We can either walk you through it or give you some insite.

[seando]

Posting new topic on the Stewart fuel pump. Pulled it off and apart. No sign of fuel.