Carburetor Adjustment, stalling - backfire

Unknown
Unknown
edited November -1 in HUDSON
For the first time a quite a few months, I took my Super Six out for a short drive. I noticed a few things.



Even at idle, when I press the accelerator, I have to be careful not to stall the engine. Sometimes it will pop, and then stall. This should be a classic sign of something. I've heard it means the carb isn't getting enough gas. Dirty filters?



I changed the filters recently, but the carb itself may be dirty.



I smell gas as I idle, so I'm wondering if the mixture isn't too rich. I don't think I've ever properly adjusted the carb.



Any ideas?



-Chris



Carter carb, on a 308. "Single H" power :)

I have a Twin H setup that I might install one day.

Comments

  • [Deleted User]
    [Deleted User]
    Lots of possibilites for the remote diagnois to consider Chris.



    Is the choke sticking? Does the automatic choke allow the choke plate to open as the engine warms up?



    What about the timing? Points set to the proper gap? Distributor at the appropriate setting for the gas octane and altitude of use?



    All that being right... vacume leak at the carb? Are the carb mounting bolts tight? Is the carb air cleaner mounting bolt too tight on the air horn? If so this will stick the choke plate.



    Back fires are usually an artifact of timing vis a vis fuel... but not always.



    Start with the obvious ... do the eye ball checks and then check point gap, make sure the cap is clean and without carbon tracks or cracks. Replace check, if not improved, check the carb for the things listed above. adjust the idle and mixture to optimum. If all else fails check back chat history... believe there is a thread on resetting the float level due to gasoline octane.



    GOOD LUCK
  • junkcarfann
    junkcarfann Expert Adviser
    This sounds like a classic symptom of the accelerator pump not squirting enough fuel, resulting in a lean condition when the gas pedal is pressed down.



    Pressing the gas pedal down opens the throttle plate, which lets the engine quickly inhale a large quantity of air. If there is no corresponding increase of fuel at that precise moment, the engine goes lean, resulting in stalls, stumbles, and sometimes pops, as you describe.



    The accelerator pump gives a shot of fuel, like a squirt gun, to richen the mixture to the acceptable air-fuel ratio.



    If the pump is still functioning, but not at 100%, You can quickly pump the gas a few times as you accelerate the engine, (actually its a partial quick few pumps, not to the floor). If the pump has anything left, it will squirt some gas to at least partially overcome the stumble.



    The fact that this happened after the car has set for "quite a few months" further points to the accelerator pump, as it is made of leather which will dry up and crack.



    It could be in the ignition, but I seriously doubt that your points went bad, or your ignition timing got changed, while the car sat idle for a few months.

    This is assuming the car ran ok before it was parked.



    It is more likely that, if ignition related, moisture has entered the distributor cap. You can do a quick remedy of that by popping the cap off the distributor with wires still attached, and spraying WD40 on the inside of the cap. The WD40 will displace the moisture and allow proper distribution of the spark.



    A good ignition tune-up can never hurt, but it sounds like its in the carburetor, especially the gas odor at idle. That could be the choke sticking, or a leak that is more noticeable at idle because when the engine is revved up the fan blows the odor away.
  • Unknown
    Unknown
    Thanks all for the help. It looks like the timing was just a little off. I really should time it properly. What I did was turn the dist a little to the right first and the car wouldn't start. Then I turned it to the left of where it originally was, and it seems to run great.



    Just about all the parts are new. I rebuilt the carb after having this problem the first time. Yes, accel pump not working would also exactlly explain what's going on. I also noticed (4 years ago,when I rebuilt the carb) that the throttle would stick down, also due to a worn out accel pump.



    I'll drive the car around a bit. I think it's ok now, but would like to get my hands on some numbers. What should the timing be? What marks on the fly wheel should I be looking at?



    Thanks again for the help

    -Chris
  • [Deleted User]
    [Deleted User]
    usgrant7 wrote:
    Thanks all for the help. It looks like the timing was just a little off. I really should time it properly. What I did was turn the dist a little to the right first and the car wouldn't start. Then I turned it to the left of where it originally was, and it seems to run great.



    Just about all the parts are new. I rebuilt the carb after having this problem the first time. Yes, accel pump not working would also exactlly explain what's going on. I also noticed (4 years ago,when I rebuilt the carb) that the throttle would stick down, also due to a worn out accel pump.



    I'll drive the car around a bit. I think it's ok now, but would like to get my hands on some numbers. What should the timing be? What marks on the fly wheel should I be looking at?



    Thanks again for the help

    -Chris





    Chris



    Timing the engine will require you to use a timing light that allows you to place it so you get a NO PARALAX view of the hole just above the starter... drivers side of the engine. By looking just above the radiator you can view the hole and determine what LINE on the flywheel the timing light is illuminating. Note you need to have the timing mark metal pointer installed to determine the mark. Moving the distributor will advance or retard the timing and the marks at which the pointer aligns will naturally change. The vacuum advance needs to be disconnected and plugged. The point dwell must be precisely set .020 inch per the Hudson Manual. The flywheel face is marked "CYL-UDC-1" then there are five lines engraved into the flywheel. Those marks can be seen through the window above the starter. Using the starter solenoid button move these lines into view. Using chalk or a paint marker color in the longest line so that when the timing light illuminates the flywheel you can see the line clearly. The manual indicates you can time the engine for 1-6 via these lines. My mentor Bernie Siegried told me that minimum of 6 degrees of advance was need for a Hornet to run properly. I believe he meant this for an engine that was mechanically good and the carburetor was set properly.



    If you do not have a timing light the following is the Hudson manual procedure for setting the timing. BTW this will account for the octane of your gas too as it will optimize your timing based on all variables. Make sure you set the idle to 540-550 RPM.



    To set the timing without a timing light, remove NO. 1 spark plug and crank the engine until NO 1 Piston starts on the compression stroke. Continue cranking until the Long line on he flywheel lines up with pointer. Loosen distributor quadrant screw and rotate distributor clockwise to the limit of the slot in the quadrant. Remove secondary wire from the center of distributor cap and hold bare wire end of wire about 1/8 inch from the cylinder head. with ignition switch on, slowly rotate the distributor counter-clockwise until a spark jumps from the wire to the cylinder head; then tighten the quadrant screw.



    Correct ignition timing is indicated by a slight "ping" at about 15 MPH when accelerating at full throttle from 10 MPH in high gear. If no ping is heard, timing should be advanced one quadrant gradation mark at time until the ping is heard. Under no circumstances should the pointer at the flywheel opening be more than one inch (first short mark) before the UDC mark when the spark occurs. If too much ping occurs or if the engine pings at higher speeds, timing should be retarded by rotating the distributor clockwise one gradient at a time.



    Good Luck with your car.



    My website has the following link....



    http://www.carnut.com/specs/gen/huds50.html
  • Unknown
    Unknown
    Heart ot Texas;



    Excellent! What great detailed instructions. I would not have thought to disable the vacuum advance. I'll try to get that done today.



    -Chris
  • junkcarfann
    junkcarfann Expert Adviser
    I respectfully disagree with the above recommendation to advance the timing until it pings, then back it off.



    It is my understanding that today's gasoline is considerably higher in octane than the gas of fifty plus years ago.



    Therefore, it is possible to advance the timing until it pings, back it off, and still be more advanced than is healthy for the engine. This is because the higher octane will not allow for pinging at the point where the antique gas would.
  • Unknown
    Unknown
    The big change I suspect is converting to 12 volts. That shouldn't have changed the timing, but I wonder if the points fire off and chage the coil just a little sooner than they used to.



    It runs pretty well now, but I can still make the engine caugh when I press the pedal.



    I'm not sure which way the rotor is moving. If I turn the cap to the left does that advance or reterd the timing?



    -Chris
  • Uncle Josh
    Uncle Josh Senior Contributor
    Take the distributor cap off and turn the engine with the starter. The rotor will be turning clockwise on a Stepdown 6.



    Therefore, rotating the distributor counterclockwise will cause the points to meet the rotor sooner, thus advancing the timing.



    I suspect your caugh is carb-related however.



    Shoot, I thought the new gas was lower octane, requiring more advance than spec.
  • Unknown
    Unknown
    junkcarfann wrote:
    I respectfully disagree with the above recommendation to advance the timing until it pings, then back it off.



    It is my understanding that today's gasoline is considerably higher in octane than the gas of fifty plus years ago.



    Therefore, it is possible to advance the timing until it pings, back it off, and still be more advanced than is healthy for the engine. This is because the higher octane will not allow for pinging at the point where the antique gas would.



    Not exactly the case, from a physics point of view. The higher the octane, the slower the fuel burns. Therefore to get the proper combustion from a higher octane fuel, the ignition timing MUST be advanced. As long as you're not getting a ping, there's no potential for engine damage. Some earlier, lower compression engines will not ping on 87 octane fuel no matter where you advance them. The optimal remedy is to raise the compression ratio. If you're not engine building though, you can usually find a good number a few degrees advanced of the factory setting that will work fine. If you stick with low factory numbers for advance when running a higher octane fuel, you'll have the mixture combusting late, which will result in not only a loss of power, but a danger of burning up exhaust valves.



    In this respect, it is the fuel requirements moreso than the engine requirements that dictate the proper timing setting.



    Best Regards,
  • Unknown
    Unknown
    jamcoats wrote:
    In this respect, it is the fuel requirements moreso than the engine requirements that dictate the proper timing setting.



    Best Regards,



    In order to handle todays fuels, you suggest that the timing be advanced by how much? :confused:
  • Unknown
    Unknown
    If you're engine is high enough compression to ping on 87 octane, then Ken's method mentioned above will, as he said, account for all variables. Once it pings under a "lug" you know that's too much, and back it off a couple of degrees. If it's ancient, like my 29, you're not going to get it to ping, and you may just want to start out a few degrees (say, 3-4) advanced of the factory setting. More than that shouldn't be necessary. For example, the manual on my '29 suggests 3 flywheel teeth BTDC. I set mine at 4 teeth, which on a 118 tooth flywheel, would be 3.05 degress more advance than stock. Really I could probably go to 5 teeth, which would be 6.10 degrees more than stock, but I have babbitt in there, if you know what I mean!



    If you are setting your timing to a specific number at idle, then make sure you're below 600 RPMs, which is where the centrifugal advance on most Hudson engines starts to be employed.



    If you have a timing light that has an advance scale on it, run the engine up to where the auto advance is fully in (usually 2500-3000) and check the timing at that point. A good typical number for most engines is 36 degrees, and that would give you something to start with. This is referred as your "total timing" number. Anything in the 32-38 range should be fine.



    Also you can set your timing with a vacuum gauge. Advance the timing at idle with the vac advance disconnected until you achieve the highest vacuum reading, then retard the timing about one pound. This method is the best way to start if you want to do a performance curve on your distributor by modifying the advance weight springs (I can cover this in more detail if anyone is interested). Once you set it with a vac guage check the total timing and see if it's in the 32-38 degree range.



    Hope this helps.
  • Unknown
    Unknown
    So if the timing is too advanced, what kind of engine damage can occur? Also, numbers being numbers, isn't the octane raiting constant? 87 octane then is 87 octane now?.. or was gasoline not marked back in the day?



    It really does seem as though the timing is retarded. I rebuilt the Carter approx 2000 miles ago (3 years), and indeed the last time I had this problem was due to the accelerator pump.



    Now I suspect the conversion to 12 volts means the timing is somehow different.



    I think I'll try the "advance to ping and back off" method, unless pinging really does damage the engine.



    Thanks again. This is all great info!



    -Chris



    I'm even more tempted now to install electronic ignition. It just makes sense. Does anyone know who sells one? Hemmings?
  • Jon B
    Jon B Administrator
    What kind of engine damage? I believe that if the timing is too far advanced, pre-detonation (as the piston is actually rising) can not only blow a hole in the piston, but unduly wear the piston rod bearing (by putting extra stress on it).



    I myself tried the 'vacuum method' on my '37 in hopes of advancing the timing enough to get better mileage. Afterwards, it didn't 'ping' during lugging, but at the high end of each gear range (when the engine is racing) I got a rat-a-tat from the engine -- and it only went away when I set the timing back to EXACTLY u.d.c. -- frustrating.



    I've been told that this is because on cars with the early (non-vacuum advance) distributors, the pinging occurs at high, not low, rpms.



    I'd love to advance the timing a bit, but don't see how I can do that without endangering the engine.



    By the way, my flywheel seems to only have a couple of marks on it...not degrees. Next to the 'UDC 1-6' stamping, there seems to be an 'H', then a vertical stroke (I) which must be the actual u.d.c. mark. But how I figure out what '6 degrees' is, is beyond me! And then there is a SECOND UDC mark on the flywheel (I forget...it says UDC - 2-8 or something). Confusing.
  • Unknown
    Unknown
    When you converted to 12V, did you use the correct coil or coil resistor combination?. If you are not using a heavy enough wire to your coil, your coil will get very hot,break down and cause what you are discribing. You have to remember even tho you have converted to 12V, your distributer is still 6V due to the resister in the circuit
  • Unknown
    Unknown
    I did get a 12v coil, but no ballast resistor. I wonder if that's part of the problem. Now I'm getting no ping, and it runs pretty well as I said. But it could probably run better.



    Ignition during the compression stroke does indeed sound like a bad idea.



    -Chris
  • Unknown
    Unknown
    Yea, That would cause the problem. 2 types of coils are generally available, 1 with an internal resistor like what was used on GM products and Ford and 1without that was used on Mopar with a external resistor, which I perfer. Make sure you us at least a #12 wire from the switch to the resistor and coil. also use a Ford starter selinoid, so you can bypass the resistor on starting. Makes a very quick starting engine. I have used this system for quite a few years on my T8 Coupe and the car always is running after the second revolution of the engine. I also use a Delco 2 WIRE altenator hooked thru the idiot light, not a 1 wire altenator .
  • Unknown
    Unknown
    What's the value and current tolerance of the external resistor?



    -Chris
  • Unknown
    Unknown
    Dont know, but I use a mopar resistor and make sure it is located where it can disapate heat easily
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