On my '27 with vaporizer carburetor I am getting a bit of hesitation when accelerating. This is a new issue as the car ran well from the time I installed the carburetor and gives me free starts when warm 9 out of 10 times. I tried to adjust the mixture but it makes no difference at all. I can close the needle all the way or open it up all the way and there is no change in the idle or top end. I am used to the sensitive mixture adjustment that all of my other T's have and am wondering if this is a quirk of the vaporizer carburetor or, if not, what needs to be done to correct the problem. The carburetor has a new seat and needle which were installed less than a year ago and when I put the carburetor on I opened it 2-1/2 turns and have not touched it again since then until today.
There's a weighted, free-swinging, bronze damper in the air intake, in front of the Venturi and behind the choke butterfly. It's there to maintain a "constant depression," or vacuum, and ensure the proper fuel-air mixture by reducing the air supply according to demand.
If that hangs up in the intake bore, then you get hesitation upon acceleration. Make certain that it's absolutely free to swing easily over its entire range of motion.
Thanks Jim I will check that. Would that also explain why I get no change when trying to adjust the mixture?
I can't say that I've heard of that symptom, but it's possible that your gravity-operated damper is stuck in one position, and this is a way to roughly fix the fuel mixture, regardless of the needle valve position. There are actually two fuel/air mixing steps: The first in the bowl with heated air, followed by vapor heating, followed by a vapor/cold-air mixing in the upper chamber.
As a rule, acceleration requires a short-lived burst of overly rich fuel-air mixture. Another way to obtain the over-saturated vapor was to use an accelerator pump, which would spray raw gas into the throat of the carburetor. The Ford/Holley vaporizer accomplishes the same thing by using the inertia of the weight at the bottom end of the swinging butterfly valve. It can only swing open so fast, and with a sudden acceleration, it takes time for the weighted valve to adjust itself to a new flow rate, establishing the correct fuel/air mixture.
There is an adjustment for the full-open position of the weighted damper. It's the slotted screw on top of the secondary mixing chamber. Turn the screw out, and it will lean-down your mixture at top speed. That's usually an altitude-dependent adjustment.
Also, make sure that your choke spring hasn't broken! That gives the same effect as a jammed swinging butterfly.
Thanks Jim. The choke spring is OK so I am going to try to adjust the damper. It seems to be free so that adjustment might just make the difference. I have a new Berg radiator and the car is running much cooler than it used to so I am also wondering if that may be contributing to the problem since it seems the vaporizer carburetors are much more heat sensitive.
I don't think that the engine temperature is an issue.
You might want to check the vaporizer plate to see if it has a pin hole in it. The plate, made of sheet steel, tends to corrode, and it can develop openings that leak exhaust gas into the heated vapor, with negative results.
Please report back when you've figured out the problem and repaired it. Your solution gets added to the corporate knowledge for vaporizer owners.
Hopefully I will be able to figure out the problem tomorrow when I plan to spend the morning following up on the suggestions others have made. I put a new hot plate in about a year ago but that does not mean there isn't a pin hole in it already. One thing that I noticed today was that the piece that threads into the top of the float bowl and holds the needle valve did not appear to be fully seated. I was able to tighten it down a few turns so I am thinking that the needle valve was not seating properly. I think it was loose from the start and backed out as I was attempting to richen the mixture over the past few months. Did not have time to run the car after making that adjustment so I won't know if it will make a difference until tomorrow.
I adjusted the mixture screw on top of the secondary mixture chamber and the hesitation has cleared up. I'm not sure why but that cleared the problem up. The hot plate does not have any holes in it and the flapper in the secondary mixture chamber is free so I can't think of anything else to check. The thing that I still cannot figure out is why there seems to be no change when the primary mixture adjustment is changed. The needle valve makes no difference. Since the car now starts well and runs OK I am not going to take a chance and play with it any more until I have a problem.
I do not understand how the slotted screw on top of the secondary mixture chamber is used as a fuel/air adjustment. Could you please explain how it works! Are we talking about the screw on top of part #6254, or Factory #2202?
Your vaporizer has a major malfunction. Your needle valve is NOT adjusting the heated vapor fuel/air mixture. It is fixed at an abnormally high fuel content. Adjusting the the top screw lets in an abnormal amount of cold air, compensating for the heated vapor, which is way too rich.
Somehow, your needle valve is not mating with the brass needle seat. It's as if the needle seat is missing, and the needle valve is grounding out at the end of the thread, instead of against the seat.
Please take apart the bowl assembly and determine if the needle valve is seating properly, or if there is some alternate leak-hole for fuel into the air-stream in the bowl.
Make sure there is a cotter pin in the shaft to limit it's travel into the adjusting rod arm. If it goes in to far it can cause a binding of the universal preventing proper needle valve adjustment.
Jim I will do that but it certainly seems like the needle is seating. I suppose it is possible that there is no seat since I never checked that but I can't believe the car would even run without a seat for the needle valve as gas would be totally unmetered. I guess it is possible that the threads on the needle valve are not cut up far enough so the needle never seats. Repro stuff being what it is that is a real possibility that I never thought of. I have a few old Vaporizers laying around and will pull a needle out of one of them and compare it to the one on the car.
There's a bit of a mystery here. Being puzzled, I went back and re-examined Ford's detailed cross-section diagram of the Holley vaporizer, and then I took apart my vaporizer to see if what I was seeing in the diagram was correct.
The vaporizer bowl assembly is nothing like a Holley NH. The bottom of the cast-iron stem into which the drain valve threads is open at the bottom, and the drain valve is open at the top. Fuel is given complete freedom to well up into the mixing chamber. The fuel makes a pool in the mixing chamber, at a height common with the height of fuel in the bowl. At the surface of the pool, the hot air coming down from the exhaust manifold rips droplets off and sends them up the pipe to the heater plate.
Question that I had never thought to ask: What's the needle valve for? If gas is allowed to pool in the chamber from a big hole underneath, then the needle valve appears to have no function.
For such a primary vaporizing setup, the float adjustment is extremely important. It sets the height of the pool surface in the mixing chamber. You might want to check it.
I hope that other vaporizer enthusiasts will read this and set me straight about the needle valve.
Jim, that is certainly a question that I would like to see answered by those more knowledgeable than I. I do not remember if the vaporizer I had on the car before was sensitive to adjustment of the needle valve. Since the car is running fairly well I think I will wait to hear what others have to say. I have a couple of parts carburetors that I am going to play with to get a feel for how they work. All I know is that in my case the needle valve makes no difference. If someone could tell us that their needle valve shuts the car off when it is closed that would help. Could it be that if the float level is high enough it overrides the needle valve?
I use a Kingston B-1 vaporizer, and I've studied it for years, but I thought I understood the Holley. Turns out, it's more mysterious than I had ever realized.
Going back over the literature, I've found a major design change in the Holly/Ford vaporizer, sometime between January and March 1927. If you have the Ford Service Bulletin Essentials, look first on page 464, and then on page 470. On the earlier diagram, the bottom of the mixing chamber has a hole drilled in it, as does the drain valve. On the later diagram, there is no such hole. The only way for fuel to reach the engine is through the needle valve, and if it is closed, the engine stops running. On the earlier setup, the engine runs whether or not the needle is closed, and it doesn't really do anything.
Looking at the 1927 instruction book, it shows the latter diagram of the mixing bowl, and it details the adjustment of the needle valve, just like with the NH.
I never realized that there was a possible change in the construction of the Holley/Ford. I examined mine, and it's definitely the earlier design.
You learn something every day.
Well Jim it sound like you got the answer I was looking for. I assume that means that the only two adjustments are the float level and the screw on the top of the secondary mixture chamber. Since the adjustment I made to that screw eliminated the hesitation problem I am inclined to leave the float level as is unless raising it would make cold starts easier. It amazes me that Ford would have gone to the expense of putting a needle and seat into a carburetor when it was not needed but I think you are correct because one day while I was driving and trying to make adjustments to the carburetor I actually unscrewed the needle valve completely and did not even realize it until I shut the car off and opened the hood to close the gas shut off. Thanks for the help. My copy of the book you are referring to is in Florida but I will definitely check it out when I get back down there after Hershey.
Old-carburetors.com Fig 3 shows an unidentified part on top of the drain-valve plug that keeps the gas from bypassing the needle valve. If this part is missing the needle valve adjustment will have no effect. (Which I found out.) New drain-valve plugs are not drilled completely through so this part is not necessary. Anyone know what this part looks like? Another problem for running too rich could be excessive corroded threads in the cast iron stem. I had to put a sealer on mine. http://old-carburetors.com/1927-Dykes/1927-Dykes-059.htm
Val: The screw on the mixing chamber that you refer was a certain length by factory specs, meant to be fully screwed down into the mixing chamber casting. It only limits the internal weighted flapper to prescribed maximum travel.
I had problem with repro gas needle not lining up with the seat.... was not entering the seat to meter the gas mixture via the mixture rod the driver can access at the dash.
Wonder if the manifold gaskets were seated and not sucking air ??? Maybe you have the same problem with the misaligned gas mixture needle & seat ???
I spent some time today with a good friend. His T has a Vaporizor, standard head, Ford coils, mostly original car. Vaporizor responsive, lots of power, worked great. ..... had signature "chugging" sound associated with the Vaporizor.... Pleasant day of driving.
You will find the gremlin in your system, and you will enjoy your T driving for a long time.
Bob I have been enjoying my T's for a long time already but this is the first later T with a Vaporizer. It does seem like a lot more trouble to deal with all of it's idiosyncrasies when you could just slap an NH on it and take off without any issues. I am going to check on the needle valve alignment but I have to admit that I drove the car over 45 miles today without any issues and got 3 free starts. I was even able to get it started with the crank when cold this morning by opening the throttle all the way, cranking it over 8 times with the choke on then turning on the switch and giving it a full turn. On the theory that " if it ain't broke don't fix it " I am inclined to leave well enough alone at this point if it performs the same way tomorrow. It clearly does not have the same performance as my earlier brass T's but I am assuming the extra weight of the '27 may be a bigger part of that than the carburetor.
Sound like your gremlin has taken a vacation . Enjoy your ride !
Further to the issue about the needle valve and the apparent by-pass, my vaporizer does not have the disc above the drain valve, but the float chamber screws hard against the bottom of the central stem so fuel can only get into the tube around the needle and jet. I have always assumed that this is how it was supposed to work. It means that the drain valve can be fully tightened to hold the float chamber against the stem, with just enough compression of the ring gasket at the top.