maximum rpm, personal choice...

TomInCologne

TomInCologne

Senior Member
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...
 
TomInCologne said:
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...
Click to expand...
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...
 
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.
 
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.
 
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.
 
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.
 
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.
 
nkaminar said:
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.
Click to expand...

Is that a Stipe IB330 cam or a Burtz 340 cam OR ??
 
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
 
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 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.
 
Terry Burtz said:
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.
Click to expand...

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


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