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Old 09-06-2010, 09:03 PM   #41
Logan
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Default Re: What is average highway speed for the model a?

on tours we usually run around 40-50. If we get on the interstate, usually atleast 45 is the minumum. If a car isnt doing atleast 45, Ive been known to leave them. I dont feel like getting run over. When i'm by myself i usually atleast try to do 60 mph on the interstate. But i do have a 4 speed O.D. But i can vouch for jordan, my brother ^^^, our sedan with mostly stock engine, besides inserts and high comp head, and stock tranny & rear end it will run 60-65 all day long. (i drive faster than he does) Every cars sweet spot is different. Thats what you have to figure out. Most bone stock cars are anywhere from 45-53 mph from what i have noticed. Another thing i have noticed is, people think they have the max rpm while driving down the road, just because the engine is revving high. But what i noticed in our sedan, is we just go through that little vibration speed of 50-55 and it smooths out past that speed and just humms.
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Old 09-06-2010, 10:12 PM   #42
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Default Re: What is average highway speed for the model a?

WOW! what a discussion I see that there are a lot of different views out there which is good! I like the response and boy I got several. I can say one thing for sure as different as each car is with it's own personalty so is the driving style of each driver! Each and every speed is "just right" for each individual whether it is at 30mph or 65mph to each his own, each person has to come up with what there "comfort speed" is and how well they trust and know there A as for me I will stay in the 40 to 45mph speed with my A but I am a slow driver in my modern car anyway I usually only do around 50 to 55 mph in it. So we have a lot of good feedback and that is what I wanted so everybody be safe whether at 30mph or 65mph and for the guys that go over that you all are just CRAZY!!!! HA! HA! If anybody else wants to ring in on this subject fill free! Thanks guys for all the posts, Robert DeBord
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Old 09-06-2010, 10:35 PM   #43
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Default Re: What is average highway speed for the model a?

My 31 sw 4 door with overdrive likes 50mph. I had up to 64 for just a short spell.
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Old 09-06-2010, 10:42 PM   #44
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Default Re: What is average highway speed for the model a?

My Coupe is essentailly standard apart from an 80 thou overbore and a 3.54 rear end and I cruise on the open road at 50 to 55mph (I have checked that with GPS ) It would go slightly faster but I get the impression that it could travel forever at 55mph . Interestingly enought I think my Phaeton with a B motor and carb is only slightly faster but gets there a lot quicker ie accleration is much better.
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Old 09-06-2010, 10:50 PM   #45
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Default Re: What is average highway speed for the model a?

I was sold on a mod that could do 65. Ha ha... I'm happy with my 45 cruiser. Some how I knew it was bs. Very happy at 45!!! Some day i'll up 65 :]' or not I don't like to stress the banger yet.'
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Old 09-07-2010, 04:56 AM   #46
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Default Re: What is average highway speed for the model a?

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How about RPM's, Anybody run a tach? What is a "safe" RPM range,with a stock motor?

Last edited by MN Stumpjumper; 09-07-2010 at 04:58 AM. Reason: Add Pic
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Old 09-07-2010, 05:50 AM   #47
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Default Re: What is average highway speed for the model a?

MN Stumpjumper good question that is what I would like to know my old 4 banger seems like it is real stressed out at speeds of more than 45 mph but may just be me since I have never drove another A besides mine so I have nothing to compare mine with. Robert DeBord
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Old 09-07-2010, 06:02 AM   #48
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Default Re: What is average highway speed for the model a?

It is not stressed so much by RPM. The stressor is imbalance and lugging.

The bearings really do not care have fast the crank is rotating. The journals are just riding on the oil and not really touching any metal. The problem is when the system is run off balance. You get the engine off balance from a physical imbalance say from a crank out of center or dynamically out of balance. You can also get out of balance when you are lugging, which I am out of the correct words to describe, but the common example is when you are in too high a gear for the speed. You can also be lugging the engine with the wrong timing setting at higher speeds.

The A should always be run at higher RPMs and you need to take time to understand the proper setting of the timing where the engine is happiest for the given driving conditions.

Keep in mind that an engine that is built out of balance will seemed stressed pretty easy as it is just not working right. By out of balance, I am being very general and including items like not breathing right because the valves are not letting it breath right.
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Old 09-07-2010, 11:37 AM   #49
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Default Re: What is average highway speed for the model a?

Mine goes 55 easy and thats what i cruse at. My biggest feer at thoughs speeds is at the moment im running 55 year old tires. Saving up for my new ones.
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Old 09-07-2010, 02:36 PM   #50
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Default Re: What is average highway speed for the model a?

i wouldnt even get it out of the drive way with 55 year old tires
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Old 09-07-2010, 03:37 PM   #51
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Default Re: What is average highway speed for the model a?

Quote:
Originally Posted by MN Stumpjumper View Post
How about RPM's, Anybody run a tach? What is a "safe" RPM range,with a stock motor?

SAE defines "overspeeding an engine" as operating it at speeds in excess of the point where peak power is produced.

The stock Model A engine produces its peak HP at 2200 rpm. In the case of my '28, with stock 4.50x21 tires and 3.78 rear, that should have me going along at 53 mph.

Theoretically, one should be able to drive at 2200 rpm "forever" w/o doing major damage to the engine.

The "babbit-pounding" Chevy six usually had its HP rated at 3200 to 3600 RPM, but then the six doesn't have the same inherent balance issues as a four (or V-8) with a single-plane crank.

Lugging isn't good for any engine, especially a "splasher" with expensive poured bearings.
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Old 09-09-2010, 05:11 AM   #52
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Default Re: What is average highway speed for the model a?

Thanks for the info Frank, most people don't use tach's. Drive by "feel". I don't want to ruin a good engine.
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Old 09-09-2010, 09:53 AM   #53
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Default Re: What is average highway speed for the model a?

One must always remember all those 80 yr. old parts that have to work together that may have cristalized that could let go. Not to be paronoid but I can't help but remember my highschool days in my 31 at 70 mph with marginal running gear.
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Old 09-09-2010, 11:14 AM   #54
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Default Re: What is average highway speed for the model a?

When I had my 1933 Chev., I would limit my top speed to 45 MPH.

One day, I was crusing along 128 in Massachusetts when a Model A pulled up beside me. He went up to 50 MPH...I thought, no Model A Ford is going to pass me ! I went to 50 too. This continued to 55 and then 60.

The chev. was starting to vibrate but I kept on going. I passed by somewhat north of 60 MPH at which time, the Ford driver gave me a "thumbs up" and smiled.

When I returned home, I found put that I had cracked the head and burned out a valve seat. I told my father what happened....he just smiled.

Marc
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Old 09-09-2010, 11:19 AM   #55
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Default Re: What is average highway speed for the model a?

thought about that yesterday on my back and forth to work, well my car normally goes on the highway around 58-60 but i do find when back it off to 50 it runs more smooth and then if i take it down to 45 it runs great all day... just my thoughts
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Old 09-09-2010, 12:35 PM   #56
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Default Re: What is average highway speed for the model a?

I had my 29 roadster up to 80,then i took it off the trailer.Then drove 40-45
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Old 09-09-2010, 02:35 PM   #57
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Default Re: What is average highway speed for the model a?

I don't have a tach; those numbers were calculated from the mounted diameter of the tires / circumference, which in turn is calculated into "revolutions per mile", which is then calculated against the ring & pinion ratio to determine the "engine revolutions per mile", which in turn gives you your engine RPM at a given road-speed...

I'm not a math geek by any stretch, just plugged through the math one day, and came up with the numbers...

I certainly appreciate driving "by feel", and mostly do that myself, but I can tell you that a Model A with 21" or 19" tires and a 3.78 rear "sounds / feels" a LOT less "busy" at 50 mph than my friend's '40 Chevy six with 16" wheels and 4.11 rear at the same speed...

I like keeping my A under 50 MPH.
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Old 09-12-2010, 09:26 PM   #58
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Default Re: What is average highway speed for the model a?

Robert: I have a 1930 deluxe coupe that is fully stock. Model A engines were designed to develop 40 HP at 2200 RPM. That translates to 48 MPH with 19" wheels and 4.75-5.00/19 tires with the stock rear-end gear ratio. Off the top of my head I think the ratio is 3.78 to 1. Anyway I installed a tachometer to check this out and at 2200 RPM the GPS registered exactly 48 MPH. I find that my A runs very smooth and happy at this speed. I also find that it will run smooth up to 55 mph. This translates to just over 2500 RPM and I do not believe this extra speed is in anyway detrimental to the engine. Lugging the A is the worst thing for the Crank bearings. Keep those RPM's up.

Love my A,

Steve
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Old 09-12-2010, 09:31 PM   #59
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Default Re: What is average highway speed for the model a?

Also if you have 21" wheels you will have to add 5 MPH to the 2200 speed of 48 getting 53 MPH
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Old 09-12-2010, 09:48 PM   #60
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Default Re: What is average highway speed for the model a?

IMHO forty two is a 'happy speed for a stock A. I drove our '29 fordor from Northern WI to SW Florida in five days and rarely exceeded 42. The little Ford was just as happy in FL as it was when we left WI. If you visit with some folks that have drive Model A's long distances, they agree with the above. Californians excepted!
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