Redline

[Dusty]

What is the max RPM for a Model A engine, at 50 mph what kind RPM would you have? 1930 Coupe with stock rear end.

thanks
dusty

[160B]

Try this link to some old posts

http://www.fordbarn.com/forum/showthread.php?t=31439

[Bruce Adams]

Sooooooooooooooooooooo?
If 55MPH is 2000 RPM, I guess in THIRD
What speed is 2000 RPM in first and second with a standard rear end, 19 inch wheels?

Thanks.

[Tom Wesenberg]

45 MPH equals about 2,000 RPM with standard rear end and tires.

[Dusty]

Originally Posted by Tom Wesenberg

45 MPH equals about 2,000 RPM with standard rear end and tires.

Thanks Tom, so redline is what or about what?

thanks
dusty

[sphanna]

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Tom is about right with his 2000 = 45 mph. RPM divided by 44 will give you the MPH. 2000/44=45. The model A is rated at 40 hp at 2200 rpm which is 50 mph. I have heard someplace in the past that the engine red lined at 2700. I do not know if this is correct. My personal red line is 2500 or about 56 mph.

[Tom Wesenberg]

I don't like to go over about 2,200 RPM with a stock uncounterweighted crankshaft. Others will say more RPM's is fine, but remember the forces on the reciprocating parts quadruple as the speed doubles. The same goes for stopping distance and forces on your body in a crash. I wish people would drive more sanely.

[160B]

I have a high compression head counterweighed crank and Mitchell overdrive and a Tach. I cruise at 2100 to 2200 rpm and consider 2600 max rpm. The below table is approximate and shows mph for a given rpm with standard gearing and with a 27% overdrive.

Rpm mph mph @ 27%
2600 59 74.93
2500 57 72.39
2400 54.5 69.215
2300 52.5 66.675
2200 50 63.5
2100 47.5 60.325
2000 45 57.15
1900 43 54.61
1800 41 52.07
1700 38.5 48.895
1600 36.5 46.355
1500 34 43.18
1400 32 40.64
1300 27.5 34.925
1200 25 31.75
1100 22.5 28.575

[Dusty]

Good info guys....THANKS!!

dusty

[Special Coupe Frank]

According to the SAE ( Society of Automotive Engineers ), "exceeding the speed at which maximum Horsepower is obtained is considered over-speeding the engine."

The stock Model A engine produces 40 HP @ 2200 RPM.

Exceeding 2200 RPM is considered "overspeeding the engine", by the SAE's definition.

In my '28 Coupe, with stock rear and 21" tires, 2200 RPM = 50-55 MPH.

I spent about a month this summer driving my coupe around with a tach hooked-up...

I learned that when I was "shifting by ear", my upshifts were around 15 mph/2000 rpm First to Second, and 25 MPH /2000 rpm Second to Hig.

Now, if you're running a balanced crank, and / or insert bearings, pressurized oil feed, you might safely get to 3000 RPM or more for "red-line"...

Unless you've got a specially-built "high-speed" engine, I'd play it safe.

Good luck,

SC Frank

[Kevin in NJ]

Ford told the dealers to show the customers that the car goes 60 MPH.

That would be 2640 RPM according to the formula above.

My brothers (before a rod had a babbitt failure) coupe ran at 65 MPH for a day or two going from WI to NJ. Plus a day or more at 65 on the way out. That would be 2860 rpm.

So one might conclude that are properly rebuilt to factory engine is likely to have a 'redline' out around 3000 RPM. Granted I am making some assumptions and relying on the correctness of the above posts.

After my brother replaced the rod the balance changed significantly. He lost 5 MPH off the top end. This was YEARS after the Wisconsin trip. He also tends to drive his car at 55 to 65 MPH. The rods are a big unknown as they were part of the 1970 rebuild from a shop with a horrible babbitting reputation.

The number one problem is the A engine is a failure to center and balance the rotating crank. Ford made it VERY balanced as I have outlined in the past. We know most shops have troubles coming close to an accurate grind on the crank. Then a lot of care needs to be taken in how the engine is built. Lots of details that you MUST pay attention to in building the A engine. SO we should expect a lot of engines that are NOT happy at higher rpms.

So unless the engine was rebuilt to correct Ford specs you are likely to have vibration issues robbing your engine of its full potential.

As Special Coupe Frank points out, you might want to play it safe unless you know your engine is well balanced.

[Special Coupe Frank]

I have recently been into two original engines that still have their original River Rouge Babbit... one of the engines as 88,000 miles on it, the other has 62,000.

The 62,000 miles mill still has shims on the mains, none on the rods; some cracking on the inner thrust-face of the rear main.

As long as the bearings get oil and and aren't lugged to death, the babbit can last a long, long time.

The extreme wear seems to occur in the piston / cylinder bores.

[Louis]

Dusty,
You should be able to tell by the sound and vibration if your in danger of over speeding your stock A model, All your going to get out of watching a tach. is a distraction, and shortly after, a bad wreck .
YOU CAN DO IT....

[Dusty]

Originally Posted by Louis

Dusty,
You should be able to tell by the sound and vibration if your in danger of over speeding your stock A model, All your going to get out of watching a tach. is a distraction, and shortly after, a bad wreck .
YOU CAN DO IT....

Yea I know but its more of a curiosity than anything else and whenever I'm on the interstate and not having an accurate speedo I thought it would add an extra step of safety.

Thanks all

dusty

[MikeK]

The real answer is at what point will rod throw lubrication with a dipper system become insufficient/ ineffective. Track racers with hot 4's regularly turn near 5K, but that is intermittent. On a constant cruise the 'A' starts to have wind-age problems with the dippers about 3500. I consider the redline for acceleration 3600, for cruise 2800. Your results may vary.

Since the oil feed through the dipper tray is primarily front overflow from the valve chamber, and the engine sits tilted back three degrees, wind-age takes it's toll as the oil goes from 1 to 2 to 3 to 4. Most people blame the cooling system for 3 & 4 running hotter and scoring, but the diminishing oil feed cannot be ignored. Later designs, like the B, dropped oil to the crankcase and dipper pan at several places back from the front.

[Great Lakes Greg]

I have heard that a paper clip figuratively attached to the outer edge of a crank counter weight, can weigh up to 90 pounds at high r.p.m.s.

[Kirby1374]

Originally Posted by Louis

Dusty,
You should be able to tell by the sound and vibration if your in danger of over speeding your stock A model, All your going to get out of watching a tach. is a distraction, and shortly after, a bad wreck .
YOU CAN DO IT....

Ya, gauges cause accidents......

[dave in australia]

This is only my opinion with not much to back it up, but even though the Model A can do 65 mph, if you drive it up at the top end of this, it will wear the engine out a lot quicker. My BMW will do 155 mph, but if I drive it at that speed everywhere, assuming I don't get arrested, the engine will need a rebuild in a short time. Is it worth a premature engine rebuild just to do a higher speed? I see this in aviation, a pilot will brag about leaning out his mixture to save 1/2 to 1 gallon of fuel on a journey, only to have to pay for a new barrel or a premature rebuild, at a much higher price than the cost of the saved fuel.

[Louis]

JMHO...An A model is never going to run wide open for any length of time as Dave said, If you want to go fast and ck. out your max rpm and redline, buy a BMW like Dave.

Kirby, you are right, guages don't cause accidents, but people who like to look at guages trying to fig. out where their red line is on an 80 year old 40 hp. car sometimes might .

An A model, is what it is . agin JMO.

[Jim Brierley]

Read between the lines in some of the above posts and realize that red-line and cruising rpm are not the same thing. Red-line would be the max rpm for shifting points if you are really pushing it, or climbing a steep hill. Keep the cruising rpm around 2,000 - 2200.