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09-12-2023, 12:39 PM | #1 |
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maximum rpm, personal choice...
Hi guys and gals,
my personal and completely subjective maximum rpm that i drive my engine at is 2.300rpm. My engine has not been opened up during the last 92 1/2 years and i feel that's the maximum i want to run it at. Speed at this rpm is 50mph. According to hearsay, the maximum speed for the Model A, without overdrive or similar, is 65mph. That gives us an engine speed of 3.000rpm. Do you drive your stock engine, with babbitt, with an unbalanced crankshaft at that speed? thanks for your thoughts and input... |
09-12-2023, 12:48 PM | #2 | |
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Re: maximum rpm, personal choice...
Quote:
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JayJay San Francisco Bay Area ------------------------ 1930 Murray Town Sedan 1931 Briggs S/W Town Sedan |
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09-12-2023, 02:20 PM | #3 |
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Re: maximum rpm, personal choice...
Going over (up to as fast as it will go) for short periods are fine. Like going down a hill gathering speed to go up a hill on the other side. It's the sustained speeds that seems like it eats up an unbalanced engine.
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09-12-2023, 02:51 PM | #4 |
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Re: maximum rpm, personal choice...
I'm not comfortable running much above 2200 rpm. But I have a Mitchell and an HC 5.5:1 head. These let me drive between 50 - 55 mph at 1800 to 2000 rpm, with which I am very comfortable.
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09-12-2023, 04:27 PM | #5 |
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Re: maximum rpm, personal choice...
92 year old, never rebuilt engine?
Should be in a museum not being driven at high speed. I would treat it like an elderly relative. Your a lucky guy! Enjoy. |
09-12-2023, 08:55 PM | #6 |
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Re: maximum rpm, personal choice...
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David in San Antonio 1930 ('31?) Deluxe "Wretched Roadster" Restored 1957 Alamo A’s Club |
09-13-2023, 07:30 AM | #7 |
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Re: maximum rpm, personal choice...
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09-13-2023, 08:30 AM | #8 |
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Re: maximum rpm, personal choice...
My Burtz engine seems very happy at 3,000 which is my arbitrary red line. It would probably go more but 3,000 is all I need. I usually drive it at 2,000. I have a Weber down draft.
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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. |
09-13-2023, 09:33 AM | #9 |
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Re: maximum rpm, personal choice...
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09-13-2023, 01:38 PM | #10 |
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Re: maximum rpm, personal choice...
Burtz cam, Burtz head, Burtz flywheel, and V8 disk pressure plate from the old engine.
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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. |
09-13-2023, 02:34 PM | #11 |
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Re: maximum rpm, personal choice...
The first engine I broke in easy and slow, after 500 miles I still didn’t go much over 50, in 3000 miles the rear main crumbled.
I poured and bored my own block, 2 days afterwards I knew the car would go 67, after 1000 miles I drove the whole length of PA turnpike at 65. I have done 3rd gear starts, rode the clutch pedal over 25 miles trying to break loose stuck clutch, held my foot to the floor in second to see how fast it would go. lugging around corner in third at 5 mph. How else can i see how well i did the first time . It’s been ove 40 years since, still trying to break it. did emission testing to 3200 rpm on dyno I’m not afraid I know that I have a flywheel/ crankshaft balance problem, the car moves in a circle going through about 1000-1300 rpm, I think if i fix that I can get over 70, and am looking to see if I can get to the 75 that is there |
09-14-2023, 04:28 PM | #12 |
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Re: maximum rpm, personal choice...
A measure of the maximum engine RPM is the average piston speed. This is used for engine designs from the 1960s at 18 m/sec. specified.
Our gray cast iron heavy A engine with uncertain mass balance should not be rotated beyond this limit.
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Beste Gruesse aus Deutschland, Werner Ford Model A, Roadster, 1928 Citroen 11 CV, 1947 Hercules W 2000, 1976; (with NSU-Wankel Rotary Engine), Canadian version |
09-14-2023, 07:30 PM | #13 |
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Re: maximum rpm, personal choice...
You win.
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The Master Cylinder Enjoying life at the beach in SoCal... |
09-14-2023, 08:31 PM | #14 |
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Re: maximum rpm, personal choice...
Did I do the math right? Is that a little over 5,000 rpm?
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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. |
09-14-2023, 11:09 PM | #15 |
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Re: maximum rpm, personal choice...
The maximum stress in a connecting rod is tension at TDC and at the end of the exhaust stroke.
The "New Engine" connecting rod was analyzed by FEI (Finite Element Analysis) with a 2-pound piston at 5500 RPM. The stress in the connecting rod was 19,740 PSI and the material that the connecting rod is made from has a yield strength of 135,000 PSI. |
09-15-2023, 12:14 AM | #16 | |
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Re: maximum rpm, personal choice...
Quote:
I wonder what the speed of the model A is at that engine rpm |
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09-15-2023, 10:00 AM | #17 |
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Re: maximum rpm, personal choice...
Depends on if you have a Mitchell O/D or not. I calculate ~844.50 mph. w/o O/D.
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The Master Cylinder Enjoying life at the beach in SoCal... Last edited by The Master Cylinder; 09-15-2023 at 10:06 AM. |
09-15-2023, 10:29 AM | #18 |
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Re: maximum rpm, personal choice...
Ditto JayJay's practice.
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Bob Bidonde |
09-15-2023, 10:37 AM | #19 |
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Re: maximum rpm, personal choice...
Thanks for info ... Good info on how Burtz engine runs with Weber carb.
Last edited by Benson; 09-15-2023 at 11:21 AM. |
09-15-2023, 11:42 AM | #20 |
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Re: maximum rpm, personal choice...
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