High torque engines

[Texasmark]

History has taught us...er ah me, that under square (stroke longer than piston diameter) 6 cylinder engines (for inherent balance) were what's needed to provide high torque performance for heavy loads over the long haul. Many 500 hp, 450,000 mile between overhauls in OTR big rigs have proven this fact.

So here comes Ford with their semi-current (at least) square (4.2x4.2) to over square (4.4x4.2) and on up to their (4.4x4.4) and then I learn today that they dropped the stroke 0.2" back to 4.4x4.2 and installed a turbo on more recent, larger engines.

So having had Fords as my primary mover over the years, but not being a BTO, getting by with it satisfactorily, I was just wondering how they got away with it.

Its cold and wet outside and I have nothing else to do....goodie goodie...nothing is broken. Been in the house all day working jigsaw puzzles.

 

[Janicholson]

Rpm and turbo charging makes horse power, Over square allows good volumetric efficiency (pumping action), and HP equals performance. Torque from horsepower comes from gearing and lots of it. Jim

 

[NDIHC]

I always thought a straight 8 would be a torque monster. Firing in a straight line every 90 degrees. I'm not an engineer or anything like that, just for some reason a power stroke every 90 degrees in an inline engine sounds like it would produce a lot of torque. The old Buick straight 8 was known as a smooth running engine with a lot of low end torque.

 

[DWF]

A friend of mine's father had a late 1940's Unit Crane and shovel with a flat head strait-8 Chrysler engine. I drove truck for him some when I was young. Smooth running engine, the later shovels had Chrysler 6 cylinder engines or GM Diesels. The strait 8 had a very smooth sound. I remember the Buicks really sounded nice too.
DWF

 

[NDIHC]

A friend of mine's father had a late 1940's Unit Crane and shovel with a flat head strait-8 Chrysler engine. I drove truck for him some when I was young. Smooth running engine, the later shovels had Chrysler 6 cylinder engines or GM Diesels. The strait 8 had a very smooth sound. I remember the Buicks really sounded nice too.
DWF

My dad drove my grandparent's 50 Buick from ND to California and back in around 1954 he said it ran nice and smooth and they had no breakdowns along the way. It had the 3 speed, don't remember if it had overdrive or not. I remember riding in it in the early 70s. My grandma loved that car. They bought a 71 Dodge Coronet and sold the Buick. Grandma always said she liked the Buick better. Dodge in those years weren't known for a good solid body!

 

[Fixingfarmer]

Rpm and turbo charging makes horse power, Over square allows good volumetric efficiency (pumping action), and HP equals performance. Torque from horsepower comes from gearing and lots of it. Jim

Yep by putting a turbocharger on things that shouldn’t have it they can get away with a lot. And the way people drive they want power at high rpm anyway. 8 speed transmissions are becoming common. It’s only got to last a couple hundred thousand miles and by then it’s the 3rd owners problem. The latest 4 cylinder Chevy Silverado 1500 sure says ecoboost to me. It has intrigued me though I won’t lie that little 2005 of mine is showing it’s age if I don’t have to worry about any cylinders shutting down and pay attention to signs of water in the oil and can probably stumble through installing a liquid cooled turbo when it does go out maybe in 4 or 5 years it’s time to upgrade…that 5000 dollar quote that the last employer got to change out a turbo on his f150 got my attention though. My ears perked up at that I can remember putting one on the landfills Cat compactor and it cost a 3rd of that for me to do it out on the hill. I’m betting it was 3 times the size of that little ford one and 8 times the weight

 

[NDIHC]

Yep by putting a turbocharger on things that shouldn’t have it they can get away with a lot. And the way people drive they want power at high rpm anyway. 8 speed transmissions are becoming common. It’s only got to last a couple hundred thousand miles and by then it’s the 3rd owners problem. The latest 4 cylinder Chevy Silverado 1500 sure says ecoboost to me. It has intrigued me though I won’t lie that little 2005 of mine is showing it’s age if I don’t have to worry about any cylinders shutting down and pay attention to signs of water in the oil and can probably stumble through installing a liquid cooled turbo when it does go out maybe in 4 or 5 years it’s time to upgrade…that 5000 dollar quote that the last employer got to change out a turbo on his f150 got my attention though. My ears perked up at that I can remember putting one on the landfills Cat compactor and it cost a 3rd of that for me to do it out on the hill. I’m betting it was 3 times the size of that little ford one and 8 times the weight

Does anybody know what the warranty is on the newer turbo engines? Like the Chevy turbo or the Ford ecoboost? Some have a 10 year 100,000 mile warranty, don't know about those though. The ones I work on are 10/100k. But they aren't pickups.

 

[Brendon-KS]

Long stoke engines MUST make their torque (and the resulting power that accomplishes work) at low speeds because the long piston travel limits how fast the engine is capable of running - high engine speeds and the high power that comes as a result just isn't an option when the pistons need to move so far each revolution. This slow running speed is conducive to long life but reduces the maximum specific power (the horsepower per cubic inch) that is achievable. For things like large trucks, tractors, and construction equipment this isn't a problem but for vehicles like cars and light pickups that are rarely asked to produce maximum power it is often desireable to have an engine that can produce more power for a given physical size so shorter stoke engines that can rev higher are used. The drive wheels can't tell the difference between 100 hp coming from a low speed, higher torque engine and a high speed, lower torque engine when both are geared to give the same driveshaft speed - the torque being transmitted by the driveshaft will be the same. But, if you were going to do this all the time the lower speed engine will obviously last longer.

 

[Goose]

I always thought a straight 8 would be a torque monster. Firing in a straight line every 90 degrees. I'm not an engineer or anything like that, just for some reason a power stroke every 90 degrees in an inline engine sounds like it would produce a lot of torque. The old Buick straight 8 was known as a smooth running engine with a lot of low end torque.

In the mid 1950s I had a Buick Roadmaster with the straight 8 engine, manual transmission. That thing had so much torque that when you were driving in traffic you could just leave it in second gear. It would take off from a stop in second, and easily roll along 30 or 35 mph in second. (Made it handy when I was driving around with my right arm around the gal I was dating at the time).

 

[Texasmark]

I always thought a straight 8 would be a torque monster. Firing in a straight line every 90 degrees. I'm not an engineer or anything like that, just for some reason a power stroke every 90 degrees in an inline engine sounds like it would produce a lot of torque. The old Buick straight 8 was known as a smooth running engine with a lot of low end torque.

Yeah and the single gear Dynaflow tranny in a 1950 as I recall. Mash on the gas, hear this roaring noise, car starts rolling. Never knew what kind of fuel consumption accompanied that tranny. When my sister's husband was dating her he had a Pontiac straight 8 coupe with 3 on the tree. They had to be good "torquers" with all that mass in the crankshaft. One of the problems with them was the length of the hood.....forced you into a long wheelbase.

 

[Texasmark]

Rpm and turbo charging makes horse power, Over square allows good volumetric efficiency (pumping action), and HP equals performance. Torque from horsepower comes from gearing and lots of it. Jim

Well I do recall that Ford's rear end has a fancy drive train (forget what it's called).....at least my 3910 has such.

 

[olddavid]

Had a 1972 304 cu. in. V-8 Gremlin 3-spd stick in my younger days. I could start it on even a grade in high gear. The axle was something like 3.54 to 1. It was a torque monster but not much on the high end. I now have an 2000 Integra 1.8 litre (110 cu. in.) 5-spd dohc (nonVtec) 4 cyl. Not much torque on the low end but at around 3000 rpm it feels like a switch was thrown and the power just keeps coming. In a quarter mile run the V-8 would probably win but not by much. The Gremlin red lined at around 100 mph but the former owner of the Integra said he had driven at up to 125 mph and I believe him.

 

[560Dennis]

I ve been impressed the 440 mopar over the hemi for street and track , performance

 

[dhermesc]

Long stoke engines MUST make their torque (and the resulting power that accomplishes work) at low speeds because the long piston travel limits how fast the engine is capable of running - high engine speeds and the high power that comes as a result just isn't an option when the pistons need to move so far each revolution. This slow running speed is conducive to long life but reduces the maximum specific power (the horsepower per cubic inch) that is achievable. For things like large trucks, tractors, and construction equipment this isn't a problem but for vehicles like cars and light pickups that are rarely asked to produce maximum power it is often desireable to have an engine that can produce more power for a given physical size so shorter stoke engines that can rev higher are used. The drive wheels can't tell the difference between 100 hp coming from a low speed, higher torque engine and a high speed, lower torque engine when both are geared to give the same driveshaft speed - the torque being transmitted by the driveshaft will be the same. But, if you were going to do this all the time the lower speed engine will obviously last longer.

I agree but I also remember the massive RPMs the old 300 6 in our Ford F600 would make when down shifting from 4th to 3rd while climbing a hill. It seemed the pistons were ready to jump out of their holes and swap places.

 

[1948CaseVAI]

My dad drove my grandparent's 50 Buick from ND to California and back in around 1954 he said it ran nice and smooth and they had no breakdowns along the way. It had the 3 speed, don't remember if it had overdrive or not. I remember riding in it in the early 70s. My grandma loved that car. They bought a 71 Dodge Coronet and sold the Buick. Grandma always said she liked the Buick better. Dodge in those years weren't known for a good solid body!

"Dodge in those years weren't known for a good solid body!"
That is for sure true, but as a police patrol car those early 70s Coronets would peg that 140 mph certified speedometer PDQ. Went through a lot of brakes though. But fun cars!

 

[NDIHC]

"Dodge in those years weren't known for a good solid body!"
That is for sure true, but as a police patrol car those early 70s Coronets would peg that 140 mph certified speedometer PDQ. Went through a lot of brakes though. But fun cars!

That Coronet had a 318 2 barrel but it certainly wasn't a slouch! Plain jane with rubber floor mats and vinyl seats, no ac. Driving on gravel was no fun because the dust would roll in like crazy. A hot day, no ac, had to keep the windows closed and vents off to try and keep the dust out. It only had a little over 30,000 miles on it when my grandpa gave it to my sister in the early 90s.

 

[Neil Powell]

Long stoke engines MUST make their torque (and the resulting power that accomplishes work) at low speeds because the long piston travel limits how fast the engine is capable of running - high engine speeds and the high power that comes as a result just isn't an option when the pistons need to move so far each revolution. This slow running speed is conducive to long life but reduces the maximum specific power (the horsepower per cubic inch) that is achievable. For things like large trucks, tractors, and construction equipment this isn't a problem but for vehicles like cars and light pickups that are rarely asked to produce maximum power it is often desireable to have an engine that can produce more power for a given physical size so shorter stoke engines that can rev higher are used. The drive wheels can't tell the difference between 100 hp coming from a low speed, higher torque engine and a high speed, lower torque engine when both are geared to give the same driveshaft speed - the torque being transmitted by the driveshaft will be the same. But, if you were going to do this all the time the lower speed engine will obviously last longer.

Agreed. Also, as far as I can tell, it's a myth that an oversquare configuration cannot make as much torque as undersquare. If you trade 10% less stroke for 10% more bore area, you trade 10% less lever arm for 10% more force (pressure times area) on the piston. The end result is the same twist. In other words, within reasonable limits, torque is proportional to displacement, regardless of whether the displacement comes from bore or stroke.

 

[Brendon-KS]

Agreed. Also, as far as I can tell, it's a myth that an oversquare configuration cannot make as much torque as undersquare. If you trade 10% less stroke for 10% more bore area, you trade 10% less lever arm for 10% more force (pressure times area) on the piston. The end result is the same twist. In other words, within reasonable limits, torque is proportional to displacement, regardless of whether the displacement comes from bore or stroke.

That is true and is well-demonstrated by the old GMC V-6 engine family that all had a very oversquare dimensions (for example, the 401 size measured 4.875" bore by 3.58" stroke.) However, these engines were known for their low rpm power and durability. There is much more that goes into where in the rpm range an engine produces its power than just the cylinder dimensions.

 

[Neil Powell]

That is true and is well-demonstrated by the old GMC V-6 engine family that all had a very oversquare dimensions (for example, the 401 size measured 4.875" bore by 3.58" stroke.) However, these engines were known for their low rpm power and durability. There is much more that goes into where in the rpm range an engine produces its power than just the cylinder dimensions.

Agree again. I once had a ford pickup with an over square (4.36" bore x 3.85" stroke) 460. It also had very good low-speed torque, due largely to a very conservative camshaft.

 

[MARK ROBKE]

In the mid 1950s I had a Buick Roadmaster with the straight 8 engine, manual transmission. That thing had so much torque that when you were driving in traffic you could just leave it in second gear. It would take off from a stop in second, and easily roll along 30 or 35 mph in second. (Made it handy when I was driving around with my right arm around the gal I was dating at the time).

I had a 4spd Duster, 340v8, bench seat, and I would have the girl shift the tranny! Mark.