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Old 06-29-2020, 12:56 PM   #1
Bob Bidonde
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Default Rear Wheel Horsepower & Torque

Theoretically, the power loss in a drive-line is 15 to 18% for a modern car. Lets say our old school technology Model "A" has a drive-line power consumption of 20%. Then the power at the rear wheels would be 32 HP. The same analogy applies to the engine's torque rating which is 128 Lbs-Ft @1000 RPM at the flywheel. So with a 20% drive-line consumption, that leaves 102.4 Lbs-Ft of torque at the rear wheels.
Is there a dynamometer test result for a stock Model "A" with a fresh engine and restored drive-line?
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Old 06-29-2020, 02:07 PM   #2
denis4x4
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Default Re: Rear Wheel Horsepower & Torque

My Zipper with ‘31 A running gear and a ‘39 transmission put out 60 HP at the rear wheels and a hundred something torque. The car is 1700 pounds. Engine has a 7:1 head, inserts, crank counterweights, FS ignition, headers, Weber 32/36 carb and 32# flywheel with a V8 clutch. Could have purchased at least three SBC crate motors for what it cost to get a 50% increase in HP!
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Old 06-29-2020, 04:33 PM   #3
Dave in MN
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Default Re: Rear Wheel Horsepower & Torque

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Originally Posted by denis4x4 View Post
My Zipper with ‘31 A running gear and a ‘39 transmission put out 60 HP at the rear wheels and a hundred something torque. The car is 1700 pounds. Engine has a 7:1 head, inserts, crank counterweights, FS ignition, headers, Weber 32/36 carb and 32# flywheel with a V8 clutch. Could have purchased at least three SBC crate motors for what it cost to get a 50% increase in HP!
Denis4x4, Interesting info on your engine. One of mine is similar.

FWIW: My '31 S?W Town Sedan with T-5 transmission.
My full pressure "B" engine block has: Inserts, high output Stipe oil pump (28 psi warm at 2200 rpm, 20 psi warm at fast idle), counter weighted crank with SBC rear oil seal (no drips yet @ 20k+ miles), 7.3:1 Lion Speed Head III milled .074" and relieved at the intake valve area, FSI Ignition, cast iron header (Tried tube header but no change in HP), Single Stromberg 97, Sterling Rattler flywheel with V-8 Clutch, front damper pulley.
77 HP a with 24 degrees advance at 2900 rpm. I would say almost the same as your engines output. I ran the engine up to 2900 rpm on the engine dyno (water brake) but when on the road, I shift at or near 2600 rpm. I do not recall what the HP was at 2600 rpm.
Good Day.

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Old 06-29-2020, 04:45 PM   #4
Kurt in NJ
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Default Re: Rear Wheel Horsepower & Torque

I think the power train consumption is the same or less than many modern cars, I can pull my a on level paved road with one finger, can't do that with modern car
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Old 06-29-2020, 10:39 PM   #5
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Default Re: Rear Wheel Horsepower & Torque

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I think the power train consumption is the same or less than many modern cars, I can pull my a on level paved road with one finger, can't do that with modern car



I think that's a combination of big wheels and low weight. I can push my 90's compact car (weighing around 950 kg) just as well as the A.
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Old 06-30-2020, 08:18 AM   #6
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Default Re: Rear Wheel Horsepower & Torque

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Powertrain consumption can been seen as a constant,you cant drive without it.Dynamometer results are predicated on a large number of conditions,no guarantee the dyno results are indicative of the car actually on the road.To test the validity of the speed components I bolted them on one at a time and used the dyno god gave me..best results for individual components I found in order...fuel,compression,cam tied it together.Harold Hick's stock exhaust manifold with a straight pipe gave just as good as a tube header.but no where near as sexy..
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Old 06-30-2020, 09:34 AM   #7
Ernie Vitucci
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Default Re: Rear Wheel Horsepower & Torque

So old Harold was a pretty good engine guy it would seem! Ernie in Arizona
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Old 06-30-2020, 10:23 AM   #8
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Default Re: Rear Wheel Horsepower & Torque

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Originally Posted by Jack Shaft View Post
Dynamometer results are predicated on a large number of conditions,no guarantee the dyno results are indicative of the car actually on the road.To test the validity of the speed components I bolted them on one at a time and used the dyno god gave me

A Dyno measures the power and torque at the rear wheels. By measuring the drag of the entire drivetrain it then calculates the power and torque that the engine puts out.
Sure, there is a margin of error and usually you can only compare results on the same dyno at the same temperatur and humidity, but it is a lot more precise than trying to feel the difference while driving if that's what you meant.
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Old 06-30-2020, 12:07 PM   #9
Jim Brierley
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Default Re: Rear Wheel Horsepower & Torque

Years ago I put my wide-bed on an electric dyno. On an electric dyno, you can let the dyno drive the wheels. At the time I was running a 2-port Riley conversion on a B block, stock B cam, single glass-bowl Holley carb, stock exhaust, B trans. It had 60 hp at the wheels and took 25 hp to drive the wheels and trans, I just pushed in the clutch and let the dyno do the driving. I believe percentages do not apply in this case, as Jack Sahft does. If I put my truck on the dyno today with a hot 4-port in it, the hp to drive the wheels would be the same.
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Old 06-30-2020, 01:39 PM   #10
Jack Shaft
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Default Re: Rear Wheel Horsepower & Torque

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A Dyno measures the power and torque at the rear wheels. By measuring the drag of the entire drivetrain it then calculates the power and torque that the engine puts out.
Sure, there is a margin of error and usually you can only compare results on the same dyno at the same temperatur and humidity, but it is a lot more precise than trying to feel the difference while driving if that's what you meant.
Ageed,it does put numbers to the feel.My point is those numbers vary under the best of conditions..
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Old 06-30-2020, 01:44 PM   #11
Jack Shaft
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So old Harold was a pretty good engine guy it would seem! Ernie in Arizona
He impressed Mr Ford but quickly got on his bad side,it appears Mr Hicks argued his point 'incorrectly' with Mr Ford over the main bearing issue he found with the design when he was doing his other famous work..hero in '28, gone from Ford Motor Company by '36..
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