Shifting gears

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    My 1923 Pierce-Arrow Model 33 was delivered and I had to drive it 10 miles up a mountain road to display it at a hotel.  It did not take kindly to double clutching on up-shifting.  Seems to require a direct shift.  I had little time to get used to it.  What is the best way to shift up and down?  I also have the car running on full “lean” and it is still running rich due to the altitude.  Is this an easy adjustment?  Thank you,  Larry Altherr



    Clean up shifting on an uphill is a challenge. Depending on the steepness of the hill, as you found, sometimes a straight shift works better.  When double clutching on an uphill/up shift, the shift has to be made slower, as the car is slowing down. Often times the car slows down as much or more than the engine/gears and it is not possible to make a clean shift by double clutching. Speed, steepness of the hill and engine RPM all play into it.  Find some hills of varying steepness and practice on them to see what works best. Sometimes it just isn’t possible to make a clean uphill up shift.  You should be able to make clean down shifts going uphill with a little practice. How much you rev the engine while the clutch is out/trans in neutral makes the difference along with the steepness of the hill and the speed of the car.  Practice, practice……

    Perhaps someone that has found a technique that works on uphill shifts will chime in.

    There are a number of articles in the service bulletin on adjusting the Series 33 carb.  Use the technical search tool and put “33” in the model box and “carburetor adjustment” in the title box.  I know that issues 1988-6 and 1976-3 have good instructions on adjusting these carbs. It’s not too difficult. There are good diagrams in these articles.

    You asked for easy, so first I would suggest trying to adjust the Main Jet on the bottom of the carb before going through the whole adjustment process. First center the dashboard mixture knob. Then make a note of the location of the rod that goes through the main jet screw so you can start over if need be. Loosen the clamp on the main jet screw that connects to the mixture control cable. Turn the main jet screw in a small amount. Tighten the clamp. Take it out and drive it and see if it improves. Keep adjusting until it is not running rich anymore. Vary the mixture control on the dash while driving and once you can get the mixture where you are happy using the mixture knob, pull over, note the position of the through rod, loosen the clamp, center the mixture knob without turning the main jet screw, tighten the clamp and you should be good.

    Once you get the carb adjusted where you are happy, I would suggest warming it up and driving it several miles at moderate throttle. Shut the engine off and pull over and pull a spark plug. The insulator should be a tan color if the mixture is correct.

    When you go to altitude (unless your are going really high) you should be able to lean enough using the mixture knob.

    If this doesn’t solve your problem it is possible your carb needs a more complete adjustment, or there is a problem such as reeds not opening properly or the float level is too high.  You can check the float level through the glass window on the float bowl. One other possibility is the fuel pressure is too high.  The gauge in the car should not show more than 3-4 lbs. The air pump pressure is adjustable.

    The majority of the intake air comes through the block into the back of the carb. It enters through a hole behind the water pump and through the oil filler cap. At high speeds the reeds under the round intake screen open to give the carb additional air. If they are not opening, the car will run rich at high speeds.


    I hope this helps you.


    • This reply was modified 4 months, 3 weeks ago by David White.

    Excellent, Dave!  I’d like to add that almost any Pierce, but especially dual valve cars like yours, should be run on the rich side–but certainly not belching black smoke!

    For a seat-of-the-pants adjustment (i.e., assuming you don’t have a gas analyzer), consider this:  With a fully warmed up engine, loosen the main jet clamp, have an assistant run the engine at about 1200-1500 rpm (no load, of course) while you adjust the main jet–with a vacuum gauge if possible.  That will be your base setting of the main jet itself, and under load or greater speed it will need to be a tad richer.  Since you’re at altitude already, you want to be able to lean it further for greater altitude but also to enrichen the mixture at lower altitudes.  Your call as to where you position the mixture knob for your default or “home” setting, but be sure to allow for both leaning and enrichment in the remaining travel of the knob.


    Thank you both Dave and George for your wealth of information.  The car went through a nut and bolt restoration about 20 years ago and driven very little.  It feels very tight – new like.  The most difficult car I ever learned to shift smoothly on is a PI Rolls-Royce and their mesh of gears requires almost perfect RPM timing to perfect a smooth shift.  I seemed to be better at downshifting the Pierce than up-shifting, which is opposite of what one would expect.  I believe the Pierce is more user friendly than the Rolls and I was over compensating.  I know shifting at a lower RPM is much easier but the mountains do not always allow for that.  For 1923, the Pierce drove quite well on flat ground but the lower horsepower  requires patience, slow speeds and hopefully a flagman following to keep others at bay when climbing. I’m going from 2,000 ft to 5,200 ft in 4 miles.

    I believe I have enough information to start dialing in the carburetor.  I will first set the idle jet and then test drive before I dial in the main jet.  Trial and error will work and I will always know where I started as a base line.  Thank you so much for all your help and I will check the service bulletins.  Larry Altherr


    Larry, you may want to check the 20-year-old 600W gear oil in your transmission–my experience is that it thickens with time and 20 years is twice my own interval for change.  Shifting will be stiff when the oil is cold, as you know from your R-R experience, and we should shift earlier under those circumstances, but should be buttery smooth when the oil is hot.  Restoration Supply has about SAE 250 gear oil which works well for me.  I haven’t been able to find any Texaco Thuban SAE 250 in the last few years that I found to be perfect, and I just finished the end of a 3-gallon pail from a previous owner of one of my cars.

    Shifting a crash box is half-science, half-art, and each transmission is different–so experiment with different techniques.



    George brought up a really good point about running your car slightly rich.  The dual valve sixes have a tendency to crack around the exhaust valves when hot so running them lean (hot) is not a good thing.  I set my base mixture on a level road near sea level at part throttle. Anytime I am going up a hill or pulling hard, I run the mixture richer. Check your spark plugs under different conditions to see if you are running it OK. Don’t let the car idle for any time before pulling the plugs or you will be seeing the idle mixture. Ideally, having an exhaust gas analyzer that you can use on the road would be the best way to check.

    It sounds like you have experience with non synchro boxes, so practice is a good thing. Every car shifts differently with different gear ratios and different gear spacing. Every time I change cars, I have to readjust my pause time and engine revs for that car. My two Series 36 cars shift differently because the Runabout has a higher geared rear end than the touring car.

    I will add to George’s comments about oil that you can change the shift characteristics by changing the viscosity of the oil. Heavier oil = quicker shift action needed.  I like to pause my shifts a little longer (not good for uphill up shifts) than George so I run a slightly thinner oil.  Gear oils are an entire subject on their own. 250 weight gear oil is getting harder to find in any quantity less than 55 gal. I have been looking for several years for a 5 gallon pail.

    You make a comment about slow going up hills.  Your car should do well going up hill compared most cars of the era.  Perhaps the RR you are used to was a more powerful car.  It might be a good idea to check all the ignition settings to make sure that they are correct. Also check your valve clearances. I run the exhaust valves .001″ loose from factory setting.  I have not found that I am holding up other cars going uphill (except for George in his 48hp Dual Valve, it will run just below lift off speed). Are both ignitions working?  My Runabout was running on only one ignition when I got it.  A huge difference when I got both sides working. When you check the ignitions individually, you should get a noticeable RPM drop at idle compared to both on.


    • This reply was modified 4 months, 3 weeks ago by David White.

    Thanks again George and Dave – I do believe I should have had more power driving up.  Something is off and I am dealing with unknown settings, fluids and the list goes on.  Approx. 1 mile from the top of my climb, I took the gas mixture from center to full lean and I had more power.  There is a mixture problem and it may require a full re-setting in the end.  I believe it may be multiple issues.  The engine starts easily, runs and sounds great but switching left and right ignition, one side was quite weak.  I asked for a simple fix when we all really know there is no such thing.  I will slowly go through each system as I become acquainted.  I love a challenge and have the time and few miles will be driven until I have the issues resolved.  I also have patience or at least know when to leave the garage.  I can read and scratch my head as well as the next guy and it is a labor of love to keep these cars going.  I tip my hat to the Pierce-Arrow engineers (outstanding) as well as Ron Blissit for his restoration abilities which show so well after many years.  I am keeping several cars until the end and they will be worthy for the next caretaker.  Thank you again,  Larry Altherr


    Hi Larry, I was reading about wanting to change the mixture on your series 33. Screwing the needle valve up will make it run richer. The way I usually set them is to set the knob on the dash to the middle, straight up, loosen the arm at the carburetor, unscrew the needle until it stops, then turn it 1/2 to 3/4 turn and see how the car runs and adjust from there. The other end of the needle is on a taper, so unscrewing it closes the gap and leans the car, screwing it in opens the gap and riches the car.


    Sorry, I worded that poorly.  How about; Looking from above, turn the main jet screw clockwise to lean.


    Thank you Heidi and William.  I have read more than once the description of the carburetor and its function and settings.  It is sinking in slowly and I do understand “out” is close.  I received a call from Ron Blissit, the gentleman who is responsible for the beautiful restoration years ago and have hit on another gold mine of information and he has spent countless hours with the car.  I feel it will be brought back to its full glory and provide many years of enjoyment.  Larry

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