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Old 10-29-2020, 08:55 PM   #41
Chuck Sea/Tac
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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It's amazing isn't it! Years ago we had a guy in our club took his car out with a fresh engine, installed in a shop. Drove it some, and next thing ya know it had to be towed in. Someone forgot to put cotter pins in the rod caps. TORE IT UP!

And if ya say anything the supposed engine rebuilders get mad...
I doubt it was because he forgot cotter pins. I don’t have pin in my rods. No little second lock nuts either. He forgot to torque them!
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Old 10-29-2020, 09:33 PM   #42
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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It's amazing isn't it! Years ago we had a guy in our club took his car out with a fresh engine, installed in a shop. Drove it some, and next thing ya know it had to be towed in. Someone forgot to put cotter pins in the rod caps. TORE IT UP!

And if ya say anything the supposed engine rebuilders get mad...

I say "misdiagnosis" here. Properly torqued rod nuts don't back off like that! More likely, that shop owner told the new kid to torque the rods and "Don't forget the cotter keys!" When the holes didn't line up, the kid, not having been trained, backed off the nuts until the holes did line up. And no one checked his work!
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Old 10-29-2020, 09:37 PM   #43
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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I doubt it was because he forgot cotter pins. I don’t have pin in my rods. No little second lock nuts either. He forgot to torque them!
IMO, an even more stupid thing to do.
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Old 10-29-2020, 11:46 PM   #44
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

I have a Mitchell in my 1930 Town Sedan and it cruises nicely at 55 mph., but it is also wonderful to drive it on surface streets at 45 in OD....it is so quiet and almost serene....
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Old 10-30-2020, 04:58 AM   #45
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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I have a Mitchell in my 1930 Town Sedan and it cruises nicely at 55 mph., but it is also wonderful to drive it on surface streets at 45 in OD....it is so quiet and almost serene....
Same with my Coupe.
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Old 10-30-2020, 06:35 AM   #46
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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Back in the late 1950's I bought and sold a few Model A's one summer (kept one which I still have). I sold a 30 sedan to a teenage friend of mine. It was a nice car but the motor was tired. A few days after I sold it he came back to tell me that the car would easily do 60 miles an hour. I had trouble believing him until he explained that he had approached the top of a long local hill as fast as he could go and then put the car in neutral and didn't touch the brakes all the way down the hill (about a mile long) and it was doing over 60 at the bottom. Lucky there wasn't a slow truck or a cow at the crossroads at the bottom. Teenagers!!!
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Old 10-30-2020, 03:41 PM   #47
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

I use my A for a parts chaser and sometimes drive it to town Friday nights for "bench racing and hanging out". It is capable of going easily over 100 mph and I do that quite often on a certain road. I can easily keep up with the fastest freeway traffic. The car has a cage and the seat belts are attached to the frame. I use racing oil in the B engine, have 4 wheel disc brakes and 8 inch rubber. The car looks completely stock from the outside if I put the stock wheels on. (which I do quite often)

The point being, you should not drive at a faster speed than a car is safe at and a stock A was made to go about 60 max. safely.
There is no stigma with driving an A slow. No one has to justify how they drive or the car they drive.
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Old 10-30-2020, 06:12 PM   #48
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

How would I know if I had a high speed rear end in mine? By modern standards there seems to be a big jump from second to third, is that typical on standard rear ends? My car seems happy at 50 or even 55, I'm just not thrilled about mechanical brakes at 55.
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Old 10-30-2020, 06:17 PM   #49
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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How would I know if I had a high speed rear end in mine? By modern standards there seems to be a big jump from second to third, is that typical on standard rear ends? My car seems happy at 50 or even 55, I'm just not thrilled about mechanical brakes at 55.
Well unfortunately no matter which rear end ratio you have you will still have the big jump between 2nd and 3rd gears.
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Old 10-31-2020, 07:38 AM   #50
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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I use my A for a parts chaser and sometimes drive it to town Friday nights for "bench racing and hanging out". It is capable of going easily over 100 mph and I do that quite often on a certain road. I can easily keep up with the fastest freeway traffic. The car has a cage and the seat belts are attached to the frame. I use racing oil in the B engine, have 4 wheel disc brakes and 8 inch rubber. The car looks completely stock from the outside if I put the stock wheels on. (which I do quite often)

The point being, you should not drive at a faster speed than a car is safe at and a stock A was made to go about 60 max. safely.
There is no stigma with driving an A slow. No one has to justify how they drive or the car they drive.



100 mph ! Must be the racing oil !
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Old 10-31-2020, 08:40 AM   #51
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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Old 10-31-2020, 08:42 AM   #52
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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Old 10-31-2020, 12:04 PM   #53
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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Just installed a new stock/rebuilt engine in my A from a reputable builder. I asked him if it was OK to drive it 45 to 50 mph, or if that would hurt engine life. He suggested that it would likely last much longer if I typically kept it around 40mph or less. I'm inclined to believe him as he has decades of Model A & T experience, pours his own babbits, etc., but I'm curious what the group's experience is on this. I will probably drive the car 1,000 to 2,000 miles per year, so even 30,000 miles will take a long time. If I get 20 years out of this engine that should be plenty.
Russ & Jennifer are great friends of mine, so I am not about to counter anything he has told one of his customers, -but my questions of playing Devil's Advocate is directed to the others as I want to hear from them.

So why won't your Model-A engine reliably 'live' at a reasonable speed of 60 mph?

When you do the math, at around 2,550 rpms with a 30" tall tire and a 3.78 gear ratio, the car should be traveling at 60 mph. At 2,600 rpms, the piston speed is approximately 1,841 feet per minute. The piston that Ford used is good for well over 3,000 fpm, and the crankshaft with 3 main bearings and 7.500 long rod with the original style piston & pin calculates out to be safe to a little over 2,000 fpm, -and add counterweights you you gain another 300-400.

So the truth is, the design of the engine is capable of cruising 60 mph, with spurts of 65 mph not being an issue. So by engineering standards, Ford's advertising of his car being capable of 60 mph is not false-advertising. So if your Model-A engine struggles driving past 45 mph (-just under 2,000 rpms.) then we need to determine where the issue is. So lets look at a list of items that would potentially cause engine failures being operated over 2,000 rpms;

Connecting Rods: Generally speaking, the connecting rod rarely fails on its' own. A broken connecting rod does fail however it is usually from excessive clearance around the crankshaft journal or a wrist pin failure. Based on my own engine rebuilding experiences, I would guess that 1 in maybe 30 connecting rod fails a wet crack test (Magnaflux).

Connecting Rod Bolts: While I have seen connecting rod bolts fail on Model-A rods, it is usually caused by the cap being hammered which loosens the bolt. I don't have a way to test the tensile strength that a pair of Model-A rod bolts will sustain, however I feel fairly sure that a stock Model-A rod should be able to withstand piston speeds of 3,000 fpm which would equate to 4,000 rpms.

Crankshaft: I can probably count on both of my hands the number of broken crankshafts that I have seen in all my years in this hobby. In every one that I have seen fail, it was a craftsmanship error that initiated the cause. Craftsmanship Error includes failure to properly straighten the shaft prior to grinding, failure to grind the proper radii on each end of the journal pin, and/or machining the pin too far creating a lower stage of harmonics that interferes with a cruising rpm.

Flywheel: This is another area where poor craftsmanship and tolerances WAY outside of Ford factory specification cause vibrations that cause issues through-out reciprocating areas of the engine. Crankshafts that have flanges that do not run perpendicular to the crankshaft centerline cause vibrations. Flywheel Housings that are warped cause vibration issues too. Couple those to an improperly dynamically balanced flywheel and you have a mechanical machine that wants to transfer that vulgar energy into areas such as the crankshaft or connecting rod bearings. Sure, we ultimately see the bearings fail however is it really the fault of the bearing, -or shoddy workmanship?

Piston: One thing that is often overlooked is the weight of the piston, ...and/or the wrist pin. When a piston is oversized compared to an original-sized piston (3.8750"), the extra mass equals extra weight unless the rebuilder knows to remove weight to compensate. Next, many pistons used in Model-A/B engine rebuilding today have a wrist pin that is about 100 grams heavier than what the original pin. Think about what this affects as far as reciprocating weight balance and how it affects pistons with regard to travel.

Bearings: A cast bearing (-a.k.a. Babbitted Bearings) when properly poured and machined should have twice the longevity of an inserted bearing. The reason most get a bad reputation is from poor craftsmanship from the engine rebuilder. So often, the engine is being rebuilt on a price-point where steps are omitted and the quality of materials are compromised which affects longevity. This creates a poor reputation for a process that worked well for decades simply because of perception. This list is not about debating whether cast bearings vs. inserts are better, -as both bearings when properly installed should provide many miles of 60 mph driving.

Camshaft: Many Model-A engines still use worn camshafts that affect volumetric efficiency and power bands. Adding to this, many camshafts that have been re-ground to a standard (-sometimes called a touring cam) have been found to have specs that vary from cylinder to cylinder. How do you suppose this affects engine efficiency at higher rpms.

Carburetion: This topic could be a whole chapter in itself but in a nutshell, an aftermarket economy carburetor (-such as a Tillotson) which uses a smaller venturi and jet will never flow the CFMs to keep up with speeds a Model-A engine is capable of. Even when a stock Zenith carburetor has a leaking throttle shaft or poorly flowing venturi, it affects CFM air-flow. A lean fuel mixture at higher rpms definitely makes an engine feel like it is laboring. So at this point, is the problem with the design of the engine, -or poor/faulty maintenance?

Other: This is one of those areas where there a likely a dozen-plus topics that could be discussed as to why a Model-A doesn't feel comfortable traveling over 45 mph. I would be glad to hear your theory too.


Bring this to a close, based on my own experiences it really boils down to a Model-A that is not within the original specifications in one or more areas as to why it struggles to be driven over 45 mph. I would like to hear from someone who feels I am in error in any of the above, but I think this is something that many of us know deep-down is factual however it is easier to make excuses for why it won't (-or shouldn't) do 60 mph instead of making the proper corrections to our vehicle.
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Old 10-31-2020, 06:21 PM   #54
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

With attention to detail a stock model a engine with the stock drive train will do 60 mph.Dilligent adherence to specification and proper assembly will yield the results Ford advertised.The problem arises when you want 'reasonable engine life..Ford engineering,Lawrence Sheldrick's engine team noted an issue with main bearing wear at high speed and felt a larger crankshaft journal would provide the stability needed to overcome the torsional vibration encountered.Mr Ford overruled them citing flywheel mass was capable of dealing with the issue.
Today,counterbalanced crankshaft and harmonic balancers counteract torsional vibration.At high rpm,the stock model a crankshaft vibrates like a tuning fork,flex has been estimated at .001 at the center main at high rpm (in excess of 2300 rpm). Ever wonder why a front crankshaft pulley cracks and fails? The same rule applies to the uncomfortable feeling you have when you drive the car too fast,its why 45 feels so good
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Old 11-01-2020, 12:04 PM   #55
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

60 MPH is getting to be like “what oil do you use?”.

My father received a new 1931 Model A Sport Coupe as a college (Northeastern) graduation present.

In 1962 when I got my first Model A, also a 1931 Sport Coupe. He told me two things. Stay under 45 MPH, and stay away from big hills, either up or down.

Ford advertised that the car would do 60 MPH. My Volvo will do 120 MPH. I don’t think that either the Model A or the Volvo are/were expected to be driven at those speeds on a regular basis.

I plan on pasting our 1929 Sport Coupe down to my grandson. It’s 100 percent stock. No jewelry or speed parts. It really likes speeds under 45 MPH. It’s 91 years old, has won many show trophies. It is professional maintained mechanically.

60 MPH? This to me is a high school thing. Mine is bigger and better than yours, remember those days.

Enjoy.
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Old 11-01-2020, 01:21 PM   #56
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

Brent, my A snapped a crank. I saw above where you said "failure to grind the proper radii on each end of the journal pin". He said the radius was the thing that caused the crank to snap. I sent a crank over to that big time shop in central southeast PA that had never been cut. They cut off 10, counterweighted it, balanced it, Then added 30 lbs lightened flywheel, and balanced again, them pressure plate was added, and all balanced as a unit. That's 4 balance steps. Everything was matchmarked with a spray can, disassembled and sent back to me.

In any event it snapped. Please expalin in lay terms what this is.

Thanks,
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Old 11-01-2020, 01:27 PM   #57
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

If you are in a hurry you are driving the wrong car.

If the machine shop “cut” your crank tell them you do not want it back.
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Old 11-01-2020, 02:36 PM   #58
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

You need to read the history of the A to get a better understanding of how it was really driven back when they were just cars to drive.

Quite frankly they drove the hard and fast all the time on crappy roads.

There are also many examples of A's being driven beyond abuse and they kept running. People doing runs as fast as the could all around the country.

If I remember correctly the NY city PD expected 50,000 to 80,000 miles on the engine before a major rebuild. You can bet those cars were not babied.

We have a mental set about and 'old' car braced by a mis-understanding of how the engine was built and how it needs to be rebuilt. As Brent pointed out the engine was built to certain standards. Rarely are these engines or driveline for that matter are actually properly restored to specs. It is about very close attention to details that give you a car that is as good at driving 45 as running 65.

Finally, my experience with people who say the A is only good for 45 is their car did not look safe at 25. This is often surveying the car from 10 feet away.
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Old 11-01-2020, 03:18 PM   #59
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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You need to read the history of the A to get a better understanding of how it was really driven back when they were just cars to drive.

Quite frankly they drove the hard and fast all the time on crappy roads.

There are also many examples of A's being driven beyond abuse and they kept running. People doing runs as fast as the could all around the country.

If I remember correctly the NY city PD expected 50,000 to 80,000 miles on the engine before a major rebuild. You can bet those cars were not babied.

We have a mental set about and 'old' car braced by a mis-understanding of how the engine was built and how it needs to be rebuilt. As Brent pointed out the engine was built to certain standards. Rarely are these engines or driveline for that matter are actually properly restored to specs. It is about very close attention to details that give you a car that is as good at driving 45 as running 65.

Finally, my experience with people who say the A is only good for 45 is their car did not look safe at 25. This is often surveying the car from 10 feet away.
I am trying to understand what you are saying here.

New York City Police Department Model A’s were driven 50,000 to 80,000 miles at 60 plus MPH, or they were just driven hard? Driving a car hard at 30 MPH doesn’t seem to me to be answering the reasonable speed question.

Also, saying a car likes a certain speed range better than a higher speed range, doesn’t necessary mean the car is unsafe.

Owners were being asked for their opinion on a very often talked about question. “What is a reasonable speed”.

Just because a person drives their car fast, doesn’t make it in better condition than the owner who prefers under 45 MPH. Think back to high school again.

Enjoy.
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Old 11-02-2020, 09:30 AM   #60
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Default Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life

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Brent, my A snapped a crank. I saw above where you said "failure to grind the proper radii on each end of the journal pin". He said the radius was the thing that caused the crank to snap. I sent a crank over to that big time shop in central southeast PA that had never been cut. They cut off 10, counterweighted it, balanced it, Then added 30 lbs lightened flywheel, and balanced again, them pressure plate was added, and all balanced as a unit. That's 4 balance steps. Everything was matchmarked with a spray can, disassembled and sent back to me.

In any event it snapped. Please expalin in lay terms what this is.
When you reference "He", exactly who is 'he'?

Personally, I would want to look at the crankshaft. Maybe the grinder missed a stress riser or crack when he Magnafluxed the crank? Maybe he didn't Magnaflux it?? Maybe the crank got inadvertently nicked which set up a stress riser??? I am unsure if you mean the flywheel is 30 pounds, -or whether they removed 30 pounds from the entire assembly (flywheel & pressure plate).

The reason I mentioned what I did above, is many unknowledgeable crankshaft grinders put too small of a radius on the Model-A journals. Ford specified a ⅛" radius to be ground on each pin. For a 20" x 1" (wide) crankshaft grinding stone I am paying nearly $250. If I dress each end to a ⅛" radius, then that leaves about ¾" to grind the journal pin. Many modern engines call for a radius of 0.050 to 0.070 (-vs. 0.125) which means when the grinder finishes a Model-A crankshaft, he must true his wheel removing 0.125" of the diameter of his grinding wheel. Based on useable size of his wheel, that cost him about $10.00 in material expense plus the extra time of truing the wheel. Therefore it is much easier (i.e.: cost effective) to cheat on the radius and use a radius that is much akin to a modern crankshaft.


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Quote:
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I am trying to understand what you are saying here.

New York City Police Department Model A’s were driven 50,000 to 80,000 miles at 60 plus MPH, or they were just driven hard? Driving a car hard at 30 MPH doesn’t seem to me to be answering the reasonable speed question.

Also, saying a car likes a certain speed range better than a higher speed range, doesn’t necessary mean the car is unsafe.

Owners were being asked for their opinion on a very often talked about question. “What is a reasonable speed”.

Just because a person drives their car fast, doesn’t make it in better condition than the owner who prefers under 45 MPH. Think back to high school again.

Enjoy.
I think you are trying to confuse others in your justification. Very few hobbyists have ever driven a very low-mileage Model-A, -or driven a completely restored Model-A that was taken to fine-point status, so they really have no idea of the facts or how they can be driven. For the ones that have, we will tell you that those type of Model-As have no problem driving 60 mph, ...and they feel safe & comfortable doing so. When a Model-A struggles to get to 60 mph, -or if they cause their owner to feel uncomfortable at those speeds, then YES, they are unsafe.



One other quick thing to point out. Unlike today's society where a person's word is often found not to be factual, back during the Model-A era things were vastly different by comparison. Not to imply there were not shysters or con-artists during that time period however you did not find advertising from top-level companies to be as deceiving or misleading as you do today. When Ford offered a statement in their advertising, it was very likely to have been proven factually, ...and especially when their boast or claim was used in multiple years of advertising. So to infer that 45 mph was considered "high speed" back in that era is just not factual. Therefore, a 'restored' Model-A with a properly (-and thoroughly) rebuilt engine should find it to be reasonable to be able to be driven at the same speeds as it was when new. After all, a 'restored' vehicle should be in at least the same mechanical condition and specifications as when it was new. Prove me wrong in what I am saying!!

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