How do I adjust my gas and spark linkage for best performance

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Model T Ford Forum: Forum 2015: How do I adjust my gas and spark linkage for best performance
Top of pagePrevious messageNext messageBottom of page Link to this message  By Travis Melnick -Waterford , Pa on Wednesday, July 01, 2015 - 09:38 pm:

Wondering the proper procedure for adjusting the linkage , when driving I adjust a bit for acceleration and it seems ok , then takes off and revs high , then when I adjust it back it slows down , then starves for fuel , I'm sure the carb is fine and that my issue lies in the linkage , but no idea how to rectify . Any ideas ??


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Coiro on Thursday, July 02, 2015 - 02:52 am:

Modern carburetors—wait a minute, is there even such a thing as a modern carburetor, anymore?—Well, let's run that down just for clarity:
According to Wikipedia, the last carburetor-equipped American cars were the...
1990 Olds Custom Cruiser, Buick Estate Wagon, Cadillac Brougham;
1991 Ford Crown Victoria Police Interceptor and Jeep Grand Wagoneer.

With that out of the way, relatively modern carburetors came equipped with a gizmo called an "accelerator pump," and again, Wikipedia can do a better job of explaining about that than I, so here's what they say about it:

Liquid gasoline, being denser than air, is slower than air to react to a force applied to it. When the throttle is rapidly opened, airflow through the carburetor increases immediately, faster than the fuel flow rate can increase. This transient oversupply of air causes a lean mixture, which makes the engine misfire (or "stumble")—an effect opposite what was demanded by opening the throttle. This is remedied by the use of a small piston or diaphragm pump which, when actuated by the throttle linkage, forces a small amount of gasoline through a jet into the carburetor throat. This extra shot of fuel counteracts the transient lean condition on throttle tip-in.

The Model T Ford carburetor don't have accelerator pump and the only way to get it to behave well during acceleration is to adjust the fuel mixture rich enough to be overly rich for steady cruising. _On top of that, many Flivvers prefer an overly rich mixture for starting and warm-up.

What to do; what to do? _Well, there are at least two schools of thought on this (Actually I can only think of two, but somebody out there in Forumland will think of more and I'd rather not look dumb): There's the "Set it and forget it" method and the "I enjoy a challenge" method:

If you're the type that sees the spark advance lever as having two positions, i.e., "start" and "run," you'll probably like this way of handling the mixture: _Put a magic marker in your pocket, go out and start your Model T. _After she's nice and warm, advance the spark most of the way, bring the engine up to a fast idle and slowly adjust the mixture for maximum RPM at that throttle setting. _Now, take out your magic marker and put a mark on your mixture knob that points straight ahead. _ Now, twist that mixture knob to the position indicated in this snapshot:



That's it. _You're done. _Your car should start okay and accelerate okay as well.

Now, on the other hand, if you're one of those guys who long for the days when men were men and cars had manual transmissions, choke knobs and AM radios that had to warm up before you could tune in the ball game, you'll probably prefer this other way of doing things:

Mark the mixture knob as above, but use a fountain pen or a Russian, zero-gravity astronaut pen (grease-pencil), because resorting to a magic marker wouldn't be the challenging, period-correct way of doing things.

Now, for starting the engine, turn the mixture knob counter-clockwise so that the mark points at the driver's door and start the engine (with the crank—after all, we're not taking the easy way out). _As the engine begins to warm up, slowly and gradually rotate the mixture knob clockwise until it points straight ahead. _You should be finished twisting just as the engine reaches perfect operating temperature as indicated on your motometer. _You'll catch onto the technique after a while.

Accelerate as usual, then upshift and bring the car up to whichever cruising speed is desired. _Now, with your power-setting and speed stabilized, twist the fuel mixture knob an eighth of a turn, clockwise so your cruising mixture will be stoichiometric (Look it up, but not online. _Instead use an actual bound dictionary—after all, we're not taking the easy way out). _Whenever you slow down for a curve, downshift or come to a stop, also smoothly return the mixture knob indication to the straight-ahead position so you'll have a nice, rich mixture for acceleration. _Don't forget to coordinate this with proper spark-advance technique as specified by this chart, which you shall memorize:



As both of your hands will be busy, steer with your chin or the tops of your thighs. _:-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Thursday, July 02, 2015 - 02:55 am:

It's a learning process, each car is different so there is really no one answer to your question, just ball park.
I would guess you are talking about the spray needle? Spark? Throttle?
If your question is about spray needle;
Generally you need to adjust it till the motor runs good at quick idle with the spark advanced to where it sounds best and the exhaust manifold does not get overly hot.
That failing, get a copy of the owners manual for your year. Then read it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Travis Melnick -Waterford , Pa on Thursday, July 02, 2015 - 07:20 am:

I appreciate the responses , but I guess what I'm asking about is the notches that the spark and gas lever have on the column , when I advance a notch at a time shouldn't there be an equal response by the carb ? I'm not seeing that response , is there a procedure for adjusting/bending the rod that links the carb to the lever on the column that would make that happen ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Thursday, July 02, 2015 - 07:47 am:

Does the lever at the carb react at all if you move several notches? If so, then look for wear in the various components. You can make a new throttle linkage out of thicker rod if the ears are wallowed out - I made a new timing linkage out of slightly thicker (7mm diam) rod, had to file down the diameter somewhat in the ends to make it fit perfectly without slop before I drilled the ends for cotter pins and bent them.

A little slop isn't much of a problem, sometimes a spring that holds the linkage steady in one direction helps.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Thursday, July 02, 2015 - 11:35 am:

Travis

The carb steel rod from the carb butterfly arm to the arm on the throttle lever shaft is bent to obtain the full movement of the carb lever.

See Para. 23 Ford Manual, Fig. 28.

Sometimes previous owners may have bent both the arms, instead of bending the rod. So do check the carb arm closes and opens the butterfly fully or you won't get full performance from the carb, as the 'throttle' can't open full. Then make sure when you fit and bend the steel rod, that the carb butterfly is closed with the lever at the wheel full up, and then opens the carb butterfly fully with the lever pulled all the way down.

It's simple mechanical pull of the rod, but it has to be bent to shape with trial and error for best performance.

Same with the Spark lever, the rod to the timer is bent to the proper length for correct timing, or else the engine won't be in time, and will overheat or perform poorly, with hard starting and lack of power.


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