Driving on the freeway
 

Hey guys!

I recently picked up a 52 f1 pickup with the original flathead and 3speed column shift which had been sitting for a long time. After rebuilding the usual stuff its now roadworthy and is running better and better as I drive it around the neighborhood. Gradually driving it further and further from home over the last few days I finally ventured out onto the freeway this morning. She rides surprisingly smooth out there! My dumb question is- What freeway speeds are yalls driving? I didn't want to push it past 50-ish but wondering if regular sustained driving in the 55-65mph range perfectly normal with these old machines or damaging to the motor?

Thanks and apologies for the long winded post!

Jeff

Re: Driving on the freeway
 

Rear gear ratio and tire size will determine the cruise speed.

Re: Driving on the freeway
 

What Ggmac said x2. 4.11s generally are too low for the freeway without an overdrive.

Re: Driving on the freeway
 

To help answer this question can we get some input into what might be considered an acceptable sustained rpm? I have driven coast to coast with 4.11s many times with '60s and '70s pickups, but I tend to run 3/4 tons with a 32" tire. There are formulas that determine rpm @ 60 mph. They use base numbers representing tire diameter/circumference, 5280 feet, axle ratio etc. With a good flattie cruising RPM (stock engine) established the rest is just math. So, what do we want to run our V8s at for extended periods?

Re: Driving on the freeway
 

Personally, I like to stay under 3000 rpm on the highway. That rpm with a 4.11 rear gear and 29" tire will be 63 mph. Above that rpm it just feels too busy to be comfortable for my taste. My '41 Merc with 3.54 gear and 29" tire is just under 2600 rpm at 63 mph and really runs nicely there.

This isn't to say you can't spin 'em faster...but I prefer the above.


Terry

Re: Driving on the freeway
 

A Ford flathead engine in as-built configuration will not redline under load. Valve spring float and ignition point float will limit the RPMs, and while the engine won’t sound happy at that speed, it won’t damage a healthy engine. Your ears will tell you a comfortable speed, until the red lights in your rear view mirror tell you otherwise.

Re: Driving on the freeway
 

I drove the 39 with 60hp engine at 65-70 a lot, if it dropped to 40 on hills i went to 2nd gear.
In the stock model A i have driven the length of PA turnpike at 65
The 1-1/2 ton 46 truck had a 2 speed rear, usually kept that just under 60, it usually had about a 2 ton load of flea market merchandise, the guy that bought it drove it to california in 4 days, i suspect he drove over 60.

Re: Driving on the freeway
 

Don't know what the speed limit is where the OP lives but where I live it is mostly 60, 70 in some places. People drive 70-75+ here in WA. At 60 you get scarily tailgated and the finger.

Re: Driving on the freeway
 

Must be some nasty people where you live. I drive the Inrterstate in the right lane at 50-55 MPH, and the only finger I ever see is the thumb up. People generally love old cars, and people know old cars drive slower. Never saw any anger, only smiling faces as they pass.

Re: Driving on the freeway
 

Doen here in S Florida, doing 60 will get someone pulling in front of you and hitting the brakes . Braking is far more important to me on the highway than keeping up with traffic. I usually take the scenic ( slow ) route .

Re: Driving on the freeway
 

The 3:92 rear axle ratio, as in my '52 F1, was a popular ratio in these trucks.
The "sweet spot" (where mine seems happy cruising) is around 50 mph. Thats ok by me!

Re: Driving on the freeway
 

As said above, it depends on tire size and rear end ratio. What I can add to the equation is that my '51 with a slightly modded '51 Merc engine with a set of Edmunds heads, a Rochester 2G, and a Mallory dual point cruises at a little over 70. This car has 3.55 gears and 225/75R15 tires. The engine is really happy at 2300 RPM, and starts to get unhappy at 2700 RPM.

Just plug that into your equation.

Re: Driving on the freeway
 

The Ford shop manual shows 4.27 or 3.92 ratios for the F1.

Re: Driving on the freeway
 

Thanks for the info everybody. I guess I need to see what my rear end gears I have and measure some tires. And maybe get a tachometer. Speaking of which what rpms do these motors like to spin at where do they not like to spin at?

Good stuff either way-

J

Re: Driving on the freeway
 

I drive my 52 F1 all over, I've thought a lot about this, and honestly I just don't enjoy driving it on a large highway at those speeds. Sure it'll do 60-65, but is that really why I got the truck? Here in NJ, the southern part of the Garden State Parkway is doable for a few exits, as there is no heavy commercial traffic and its a pleasant looking well designed road. I couldn't imagine bringing it on a large 6 lane interstate like the I-95 or even a large 4 lane highway, you'd be holding everyone back. Even driving on some larger thoroughfares 6 lane roads with traffic lights, with large retail box stores, I just don't enjoy driving on them with the old truck. I stick to two lane country type roads which can get you anywhere you want to go. If you plan out your trip.

Don't forget it's not only the engine that you have to think about. It's the brakes, bias ply tires if you have them, and suspension, not to mention the steering wheel- windshield if you were in an accident god forbid. The steering wheel will crush your chest in an accident. Thats why they got rid of them as early as the fifties in cars, but trucks still had them.

Re: Driving on the freeway
 

Might not be what Wiggles wanted to hear. BUT
Excellent point 52flthed,
When your truck was new those 4lanes were yet to be.
People still got around, as I do when I have my avatar buzzing.
So you give up a little TV time

Re: Driving on the freeway
 

When my 40 was sick it would only do 60 mph tops.
Replaced the ignition resistor and now will do 75.
65 is more comfortable with a 3.78 gear
It is nice to have a little more top speed.
I enjoy being the fastest car in the slow lane.

Re: Driving on the freeway
 

When I got my 54 Meteor running (with a Canadian flathead 255) in summer of 2021, I drove it all over with the factory 3 on the tree and 3.55 rear gears. It would easily do 60mph, even 70mph, but at 70 I felt it was just revving too high.

I've since installed a factory borg warner overdrive, and I will never go back to the 3 speed. I can easily do 70 and I've even cruised at 80mph. The fuel economy gets worse at 80 but at 60 to 70, I got 21 Imperial MPG! Took a 1600 mile road trip with that transmission and it's amazing.

I know not everyone would be as lucky as I was to source out an overdrive, but with the factory setup, I just didn't feel right driving long distances at 65+.

Re: Driving on the freeway
 

Personally I have never, and will never drive my flathead on anything more than two lane blacktop where life is a little more laid back and easy going. I've pushed the 52 Mercomatic to 60 mph and felt quite comfortable with the sound of the straight pipe. Plenty more travel left on the gas pedal but I was in no big hurry. Would be nice to find a six volt tach for it just to see what rpm the engine is turning.

Re: Driving on the freeway
 

Here is a calculator that will help you solve for MPH, Gear Ratio, Tire Size, or RPM from Strange.
https://www.strangeengineering.net/g...io-calculator/

IMO you will feel the sweet spot that your car and the driver are humming along at which I think varies with road condition. We are fortunate to have access to many country roads. While my flatheads are quite capable of cruising at highway speeds the sweet spot for me is at a slower speed, even with my Columbia.