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12-18-2020, 04:51 PM | #1 |
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2-3 Shift Point Speed
Shifting the old 31 Tudor from first to second can be done at a very slow speed with no problem. My question is the second to third shift. My engine lugs if I shift much below 30mph which makes me feel like I am winding it out in second higher than should be necessary. Sort of feels like I should have a four speed trans with a gear in between my actual second and third to get me up to cruising speed. At what speed do most folks typicall shift in to third ? Could my spark timing be over or under advanced to support a lower speed shift point ? Just seems like the engine is turning too slow to drive in third at 25mph or less. Watcha think ?
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12-18-2020, 05:00 PM | #2 | |
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Re: 2-3 Shift Point Speed
Quote:
Even when I have 3.54 gear ratio and a high compression head in a Model-A, I can turn a corner at 15 - 20 mph, -remain in 3rd gear and accelerate back to speed without the engine lugging or bucking. |
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12-18-2020, 05:06 PM | #3 |
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Re: 2-3 Shift Point Speed
Brent has some good comments. Go with that. But I want to add that the Mitchell overdrive splits between second and third, about half way. so that, in my car, I find myself driving in second high a lot of the time when on residential or mountain roads. I have a lightened flywheel and shit into third at about 20 to 25 or more depending on circumstances.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
12-18-2020, 05:18 PM | #4 |
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Re: 2-3 Shift Point Speed
It appears something isn't correct. I can actually start in second with very little effort If I choose. I agree with Brent, you shouldn't have to rev the engine at all. If your engine is retarded to much you will lack power.
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12-18-2020, 05:27 PM | #5 |
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Re: 2-3 Shift Point Speed
2nd to 3rd at speeds above 20 you better be double clutching! My normal up shift 2-3 is below 20 mph, I’am not lugging. Slowing down 20 to 15 mph then I may down shift, it depends on the road conditions! but I can accelerate in 3rd at those speeds. I’am with Brent that you probably have issues with your engine.
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12-18-2020, 05:34 PM | #6 |
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Re: 2-3 Shift Point Speed
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12-18-2020, 05:39 PM | #7 |
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Re: 2-3 Shift Point Speed
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12-19-2020, 03:22 PM | #8 |
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Re: 2-3 Shift Point Speed
Problem solved. Turns out I was not using enough advance. Typically I start full up on the timing lever and drop down to 1/3 to drive. Tried 7/8 to full advance and it runs fine at 20 mpg. At full advance still did not have any pinging. Suspect every engine is different, but in general, can full advance at slow speed be damaging over time ?
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12-19-2020, 08:09 PM | #9 |
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Re: 2-3 Shift Point Speed
Here is my 2 cents regarding timing. There are several people who will disagree, which is fine with me.
The timing is advanced because it take time for the flame front to burn the fuel/air mixture and build up pressure. The idea is to have the pressure fully built up at top dead center. The time it takes for the burning to take place is tied to the turbulence in the combustion space. That is why the head has a squish area to make more turbulence. As the engine speed increases the turbulence is greater and the fuel/air mixture burns faster. With some minor exception, a constant setting of advance lever will work well from idle to full speed. With my car, after starting, I set the advance two or three clicks from full advanced and leave it there. The best spot for the advance lever is different with each car and can be found by experimenting. Pick a hill and slightly retard the spark until the speed starts to drop off. Advance the spark a little at a time until the engine no longer increased in speed. The knee where the engine is performing best but advancing more will do no good is the correct advance. Some people with better hearing than I have may be able to hear an ignition knock with too much advance.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
12-20-2020, 12:02 PM | #10 |
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Re: 2-3 Shift Point Speed
Mine also likes the spark advance set about 3/4 of the way down, and on our busy surface streets here in S. California I shift from 2nd to 3rd at around 20 mph. Even though you can shift at 15 mph, there is a huge gap between those 2 gears, and I find 3rd accelerates better at that speed.
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12-20-2020, 12:42 PM | #11 |
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Re: 2-3 Shift Point Speed
Your engine runs best at 1 degree per 100 rpm,max 26 degrees..stock engine is very tolerant of improper timing. Setting the lever means your timing is correct at a specific rpm.
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12-20-2020, 12:42 PM | #12 | |
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Re: 2-3 Shift Point Speed
Quote:
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12-29-2020, 08:41 PM | #13 |
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Re: 2-3 Shift Point Speed
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12-29-2020, 09:44 PM | #14 |
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Re: 2-3 Shift Point Speed
It'll start OK but there is a great risk of it kicking back and either jamming the starter or bending the shaft.
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