I have a 30 A that runs great, except every time it comes to a stop, the engine wants to die. I can catch it with the hand throttle, by giving it some gas, as one foot is usually on the brake, the other on the clutch. It starts fine, it runs fine, except for this issue. The car has a fresh rebuilt engine, maybe a couple, 3 thousand miles on it. I has a new reproduction Zenith carb on it, maybe a couple hundred miles ago.
My second question is how the heck do you get the exhaust to seal between the manifold and pipe. I have tried a new clamp, but it still leaks
I think, "rebuilt" or not, there is either a plugged idle circuit passage or the float is not coming up enough.
That said I've never been a fan of Zenith carbs.
The have microscopic passages that plug with the slightest amount of anything that might come from the tank.
I've got an original Zenith on my Model A. Its not been off the car in at least 25 years. Great carburetors. Of course, I don't have rust in my gas tank.
That being said most "carburetor trouble" is caused by faulty ignition. Model A people are notorious for misunderstanding the symptoms of burned / out of adjustment points. Before touching anything on the fuel system pop the distributor cap and watch the points open and close while someone steps on the starter with the popout switch pushed in. I bet your points are out of adjustment, worn out, or dirty.
The issue of the car dying when coming to a stop likely has nothing to do with the ignition. Ignition issues don't present themselves only when stopping.
The most likely issue is the float level, which is set too high. The next most likely issue is either the compensator or the idle jets are obstructed.
Doug, In answer to your second question, make sure the taper on the outlet of your A manifold is perfectly 'true' and it will help if it is not rust pitted, too. Then make sure when you join the pipe together to the manifold that it does so without any binding or pressure from misalignment. Last, some suppliers (I got mine from Snyder's) offer a copper gasket that fits between the pipe and manifold. As an alternative, you might be able to do the same thing by encircling the taper near the end of it with a piece of solid copper wire, making sure there is as little gap between the ends as possible before joining the pipe and securing with the clamp.
P.S. Model A is no more off topic than Model B, C, K, or N. Grin.
On the Zenith carburetor there are two mixture adjustments. The one for high speed is connected to the choke rod which is adjusted by rotating the choke rod. When the engine is warmed up and running at about 35 mph, adjust to the point where it runs smoothest.
The other adjustment is a screw in the body of the carburetor. This screw looks like it is partially screwed out and has a spring on the shaft. This is for adjusting the idle mixture. There is also a screw on the throttle shaft which adjusts the idle speed. Try turning this screw in to make it idle faster until it will continue idling in neutral. Next sdjust the idle mixture screw by turning in until it starts to run rougn, then out until it runs rougn. The middle point between the two rough adjustments is where it will idle smoothest. Now turn out the idle speed adjustment screw until it runs slowly but smoothly. Note, it will run slowest and smoothest with the spark retarded. The final adjustment is where is runs fast enough so it doesn't stall and smoothest. Good luck.
Thanks for the responses. Every thing in the distributor is only a couple of hundred miles old, but we will give it a look over. I can take the car apart and put it back together, but I fail at the fine tuning. This will give me something to work on. I was tired of trying to fit the doors on my '21 touring. seems the door openings have shrunk in re wooding, even though all the sheet metal seems to line up, but that is another story.
On the exhaust pipe to manifold; I found that reproduction clamps are bad. I bought a bunch of originals at a swap meet several years back. Take a look at the clamp. It should have a longer taper toward the exhaust flange on the muffler pipe. also, sometimes people put the flange clamp on upside down, not noting the different taper. If you think your carb is not functioning correctly; borrow one from your club member and go for a ride.
I forgot to mention; it may be ignition, on the thought that you may want to get a new distributor cam or a good used one, Sometimes this can cause the engine to kill, because it will not idle.
All it takes is leaving the key on with the engine not turning for a minute or two. Doing that can heat up the points enough to cause the point arm to lose its temper. When that happens you lose the point adjustment.
It doesn't matter how many miles since the points were installed. It costs zero to look at the points. When the points get out of adjustment often the first thing you notice is the car won't idle, so it dies when you coast to a stop.
Concerning the exhaust flange. This is what I used to do when I had Model A's. I wrapped a few turns of aluminum foil around the joint and then installed the clamp. It shows, but it also seals the leaks.
My method of sealing the exhaust pipe to the manifold is to put a floor jack gently under the exhaust pipe to hold the flange to the manifold and then use a small ball peen hammer to"fit" the flange on the pipe to the manifold. I then install the clamp (using stainless bolts) with the jack still in place. I have no backfiring going downhill and no exhaust leak.
I don't know why the ignition system is being called into play on this. It is a high float level, OR a bad jet. The two jets in the center of the carburetor are multiple pieces put together, especially the one that screws in from the throat side Best thing to do is to take them out, clean them off, and run a bead of solder around the top of the hex area on that one, and on the one that screws in from the bottom, solder around the seam from the threaded base and the jet tube. This is one of those little details that can drive you crazy if you don't know about it. Very common problem with repro jets.
I had exactly that problem in my A many years ago. I had fitted a reproduction Zenith and that is when the trouble started. After some examination, I found that the repro., was based on the earliest A carby, and that a short time into production, a jet was fitted into the secondary well. With the repro, under braking, the 'well' would run dry with the surge of fuel, so the engine would die. I ended up using the repro top half of the carby and a genuine bottom half that had that jet. Never any trouble after that for over 100,000 miles.
I had the same problem on my last month, it was a plugged hole in the secondary well and a float that was a bit too high.
Corrected the float, cleaned out the jet and the car accelerates smoother and never stalls when stopping.
For the exhaust there is a copper crush washer that goes on the flange and an "asbestos" wrap that gets squished by the clamp.
The links above have some great detail on the Model A.
Bill in Adelaida Calif, has the right method. The only thing I do differently is to use an old manifold to pre-form the pipe by clamping it in a vice upside down. I also use some of the exhaust sealer available from the major suppliers. Smear a little around the connection and clamp the pipe to the manifold making sure the long side is down and run it for 10 minutes to bake the sealer.
Because it often is the ignition system that causes this problem. The fix is usually a free one - adjust the points to the proper gap after filing them.
It takes one minute and no tools to look at the points. Versus wasting your time disassembling a carburetor for no reason first.
Doug, My '30 Model A has the same exhaust issue. It's basically in need of a new exhaust manifold, they warp just like the T's, and then can't get a good mate at the exhaust pipe. I've tried the "donut", the asbestos cloth, even tapped in a screw on both the manifold and the pipe, that did the most good. But later this year it'll be getting a new manifold and I'm sure that'll take care of it.
When it comes to the "fine tune" stuff, I'm with you, but I found carb float adjustment helped.
I seem to go through condensers like water, usually two or three a year..how about you? Not sure why, other than that they're cheap Mexico products.
Does your 30 have the cast iron or glass bowl type sediment gas filter ?
On the cast type remove the bottom plug & use a stiff wire to make sure you have good gas flow( catch the gas in a metal can of some type).If it is the glass bowl type ,remove bowl & screen & check the gas flow.You can also remove the carb., & check the flange on the carb. with a straight edge to make sure it isn't bowed,along with the intake manifold flange.I had this problem years ago with my 31.
I use the insert pipe that goes into the exhaust manifold and also into the exhaust pipe. The smaller end goes into the exhaust pipe. I do make sure that my exhaust pipe lines up directly with the exhaust manifold. Often you have to slightly bend the exhaust pipe and muffler to get the straight up alignment. I use muffler paste in a tube around the flange. The insert pipe makes it easy to run a bead of the sealant around the flange. The I jack it into place with a floor jack and put on the clamp correctly as the other guys said.
Stalling for me has always been the float level since the gas sloshes forward during a stop
What Scott says brings to my mind a thing which happened when I was in high school. I had a Model A and was driving it to school. It was all downhill, and when I came to a signal the engine stalled and I could not get it to start. I opened the hood and found the carburetor hanging by the fuel line and the choke. The two bolts which hold it to the manifold had come out. Even if those bolts are loose but not out, you will suck in air which will lean the mixture and cause the engine to stall. It might run OK at higher speed, but not at idle.
I notice a lot of "A" folks having lots of trouble with condensers. I wonder what the issue is? I use old NOS ones and they seem to last forever.
Royce - I think one problem is the fact that the condenser is so close to the top of the exhaust manifold. I would think that all that heat sure can't help a condenser to last a long time! In fact, there have been a couple "accessories" made to help deal with the heat problem. One is a heat shield that fits under the distributor and deflects some of that exhaust manifold heat away from the condenser. I see that there is now also a "modern" accessory top plate (the plate that the points mount on) that also has the condenser installed right next to the points (like most "modern" distributors, and I think one reason for that is to keep the condenser away from some of that heat,.......harold
Being Easter, we did not get to the A until late this afternoon. The exhaust leak is gone now, it was a combination of errors. The car came to us as a restored car from probably at least 10 years ago, that was never fine tuned, and being our first experience with an A, beginner's errors prevailed. The car came with an exhaust leak. The clamp that came on the car was a pair of stamped parts, some heavy wire and one nut and bolt. There was nothing between the manifold and exhaust pipe, no kind of gasket. I bought a replacement that is two cast iron halves, with 2 nuts and bolts. We had one side on correct, but the other side was upside down. We took the time to loosen the rear tailpipe hanger, so we could align the pipe correctly. We had already used a floor jack to lift the pipe up to the manifold, but had not taken a hammer to the pipe to make it match correctly before. With the pipes fitting better, this time the "cheater" pipe fit into the assembly, and the gasket would stay in place. Since I had some 2" aluminum tape, I wrapped the joint. before putting the clamp on.
The stalling om stopping issue was also beginners error. the adjustment knob on the dashboard was forgotten and was completely closed, When opened about a turn and a quarter, the problem went away.
After a test drive to get the car fully warmed up, now it needs the idle set a little faster, but is quieter, and runs better - learning curve you know.
Needing to have the Gas Adjusting Valve opened a turn and a quarter sounds a little excessive to me. Most Model A's I've driven like to be open about a quarter turn, maybe a little more if it's cold out, maybe a little less if the adjustment needle or seat are worn.
Thank you for this O.T. subject. Need more of them. Good info!
My A runs best with the needle valve closed. I open it about 1/8 turn for cold start in cold weather, but otherwise, I don't usually mess with it. I thought this odd, but found it wasn't unheard of and maybe not even uncommon.
My A began trying to go dead at stop lights about the time they introduced E-10. It only does it on hot days after running down the highway. Funny, but I found if I opened the needle valve a very hefty amount, it would indeed idle. Otherwise, I had to sit and rev the engine to keep it running. Of course, it won't run down the road like that, so I had to turn it back in when I pull off from the light. But I know this is not right. I'm not sure what is going on. Vapor Lock is probably not the right term, but it's something like it. What I have found that solves the problem is about 1/2 gallon of diesel added when I fill up with gas. Go ahead and laugh. It worked for me. And like I say, I only have to do it in the summer.
My car also used to run best with the needle valve closed, but needed to be opened just a tiny bit in order to not die at idle. I was running a Zenith-1 that has the adjusting needle seat machined into the casting, and after years of use that seat got worn and because that seat was so worn I couldn't get the carb adjusted lean enough and that was also why it ran best when closed. I just finished rebuilding a early 1928 double venturi carb and installed it tonight. It runs like a brand new car with considerably less vibration, more power, and will really "count them off" at idle with the spark retarded.