The Ford Barn

TomInCologne · 09-12-2023, 12:39 PM

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...

JayJay · 09-12-2023, 12:48 PM

Quote:

Originally Posted by TomInCologne

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...

Tom - I don't have a tach, but I drive my '31 comfortably at 50-55mph indicated (actual may be a couple lower) on a smooth freeway. On downhills I've seen it creep up to 60+ indicated until I back off, but it doesn't feel comfortable there. Stock (unbalanced) crank, babbitt bearings, 5.2 head, 0.080" over bore. Stay tuned a year as I'm going to install a Mitchell O/D as soon as it comes...

Gene F · 09-12-2023, 02:20 PM

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.

Oldgearz · 09-12-2023, 02:51 PM

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.

WHN · 09-12-2023, 04:27 PM

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.

David in San Antonio · 09-12-2023, 08:55 PM

Sponsored Links (Register now to hide all advertisements)

Babbitt, not balanced, very old rebuild (or perhaps engine swap). 60 mph verified by GPS which matches the speedometer rebuilt by Morris Eddie. The engine does not feel happy at that speed and I seldom push it that hard.

old31 · 09-13-2023, 07:30 AM

Quote:

Originally Posted by WHN

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.

x2!

nkaminar · 09-13-2023, 08:30 AM

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.

Benson · 09-13-2023, 09:33 AM

Quote:

Originally Posted by nkaminar

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.

Is that a Stipe IB330 cam or a Burtz 340 cam OR ??

nkaminar · 09-13-2023, 01:38 PM

Burtz cam, Burtz head, Burtz flywheel, and V8 disk pressure plate from the old engine.

Kurt in NJ · 09-13-2023, 02:34 PM

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

Werner · 09-14-2023, 04:28 PM

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.

The Master Cylinder · 09-14-2023, 07:30 PM

Quote:

Originally Posted by Werner

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.

You win.

nkaminar · 09-14-2023, 08:31 PM

Did I do the math right? Is that a little over 5,000 rpm?

Terry Burtz, Calif · 09-14-2023, 11:09 PM

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.

DkFordor · 09-15-2023, 12:14 AM

Quote:

Originally Posted by Terry Burtz, Calif

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.

On a less serious note: That must equate to a maximum rpm range around 37,000 rpm

I wonder what the speed of the model A is at that engine rpm

The Master Cylinder · 09-15-2023, 10:00 AM

Quote:

Originally Posted by DkFordor

On a less serious note: That must equate to a maximum rpm range around 37,000 rpm

I wonder what the speed of the model A is at that engine rpm

Depends on if you have a Mitchell O/D or not. I calculate ~844.50 mph. w/o O/D.

Bob Bidonde · 09-15-2023, 10:29 AM

Ditto JayJay's practice.

Benson · 09-15-2023, 10:37 AM

Quote:

Originally Posted by nkaminar

Burtz cam, Burtz head, Burtz flywheel, and V8 disk pressure plate from the old engine.

Thanks for info ... Good info on how Burtz engine runs with Weber carb.

Terry Burtz, Calif · 09-15-2023, 11:42 AM

Quote:

Originally Posted by DkFordor

On a less serious note: That must equate to a maximum rpm range around 37,000 rpm

I wonder what the speed of the model A is at that engine rpm

NO, stress increases by the square of the speed. If you double the speed, stress increases by 4 times.

09-12-2023, 12:39 PM	#1
TomInCologne Senior Member Join Date: Aug 2021 Location: Germany: Cologne and Witten Posts: 305	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, 02:20 PM	#3
Gene F Senior Member Join Date: Mar 2012 Location: Ohio Posts: 1,973	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.

09-12-2023, 02:51 PM	#4
Oldgearz Senior Member Join Date: Aug 2020 Location: Sagle, Idaho Posts: 359	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.

09-12-2023, 04:27 PM	#5
WHN Senior Member Join Date: Mar 2017 Location: Connecticut Shoreline Posts: 1,824	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
David in San Antonio Senior Member Join Date: Sep 2022 Location: San Antonio Texas Posts: 222	Re: maximum rpm, personal choice... Sponsored Links (Register now to hide all advertisements) Babbitt, not balanced, very old rebuild (or perhaps engine swap). 60 mph verified by GPS which matches the speedometer rebuilt by Morris Eddie. The engine does not feel happy at that speed and I seldom push it that hard. __________________ David in San Antonio 1930 ('31?) Deluxe "Wretched Roadster" Restored 1957 Alamo A’s Club

09-13-2023, 08:30 AM	#8
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,900	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. __________________ 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, 01:38 PM	#10
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,900	Re: maximum rpm, personal choice... Burtz cam, Burtz head, Burtz flywheel, and V8 disk pressure plate from the old engine. __________________ 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
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,159	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
Werner Senior Member Join Date: Jan 2019 Location: Germany, near Aachen Posts: 1,159	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. __________________ 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, 08:31 PM	#14
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,900	Re: maximum rpm, personal choice... Did I do the math right? Is that a little over 5,000 rpm? __________________ 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
Terry Burtz, Calif Senior Member Join Date: May 2010 Location: Campbell,CA, USA Posts: 319	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, 10:29 AM	#18
Bob Bidonde Senior Member Join Date: May 2010 Location: Long Island, NY Posts: 3,472	Re: maximum rpm, personal choice... Ditto JayJay's practice. __________________ Bob Bidonde