No, because the torque is multiplied by RPMs. Let’s try a fictional example: Let’s say your max torque is 3 foot-pounds at 8,000 rpm (yeah, I know–bear with me). 8,000 x 3/5252 = 4.57 HP.
Let’s say that your torque drops to 2.5 foot-pounds at 10,000 rpm; 10,000 x 2.5/5252 = 4.76 HP. See? The max horsepower will always be at a higher rpm than max torque.
That’s assuming that the equation is accurate; I wouldn’t know, I just like math.
It has always been my conspiracy theory that diplacement measurements were switched to liters in the 80s to disguise how small the engine had become. Of course, as has been pointed out above, displacement and power are not always the same.
I agree with saoirse. Wasn’t it in the 80s that Ford started selling Mustangs with 2.2 liter engines?
I don’t think Ford could’ve sold quite so many if people realized that 2.2 liters equals 135 cubic inches.
To make it really simple, engines develop power by breathing in air into which fuel is mixed, then burning same. Engine size (nowadays given in liters, given in cubic inches decades ago for American cars) is essentially the “lung capacity” of the engine (bigger lungs = more power). It is not a measurement of how much oil it holds. There are some engines whose oil capacity equals their breathing capacity, but that’s purely coincidental.
Chevy350/5.7…349.98…347.8368
Ford302/4.9…300.86…299.0176
Chevy454/7.4…454.36…451.5924
From this handful of engine displacements (the only three dual displacements I know for sure;) ) the 61.4 conversion fractor appears more accurate than the official CF of 61.024.
(btw, 61.4 came out of a pocket dictionary…go figure:rolleyes: )
As for the constant 5252, I don’t know why its significant other than the fact that that is the rpm that makes torque=hp.
Perhaps it has something to do with the linear concepts of Newtonian Force and Work and Power translated into rotary form,
using the units of feet and pounds.
Would the metric units of kilograms and meters, producing Newtons and Kilowatts, produce a different constant?
I don’t see how it can be 61.4. One liter is defined as 1000 cubic centimeters, and one inch is exactly 2.54 cm, so one liter is 1000/(2.54)^3=61.0237 cubic inches. It has nothing to do with force or rotation.
Without actually sitting down to derive it, I’m pretty sure that they would.
AFAIK, there’s nothing really significant about 5252 rpm. At that speed, power measured in horsepower and torque measured in foot-pounds happen to be numerically the same. Measure either quantity in another unit, and they won’t be.
Clearly, if you measured power in BTU/hour and kept your torque measurement in foot-pounds, you’d get a different constant (1 BTU/h = 2544.4 hp).
I get nervous when I see equations presented in such a unit-dependent fashion, although I appreciate the convenience they give.
Enola Straight,
The discrepancy you’re seeing is from rounding (and sometimes PR, as you’ll see). Here are your examples redone:
—Engine---------------Bore--------------Stroke---------c.i.-----liters----c.i./61.4—c.i./61.0237
Chevy350/5.7:------4.00", 10.16mm----3.48", 8.84mm------349.84----5.732------5.69-------5.732
Ford302/4.9:--------4.00", 10.16mm—3.00", 7.62mm-------301.59----4.94-------4.91-------4.94
(not quite 5.0, is it?)
Chevy454/7.4:------4.25", 10.795mm–4.00", 10.16mm-----453.96-----7.439------7.39-------7.439
As you can see, the correct number to divide by is 61.0237, NOT 61.4. The reason 61.4 gives close results is that it’s a small difference and makes the Liter number a bit higher (and engine numbers are NEVER rounded down, only up. for PR reasons)
Here is the explanation for the significance of the constant 5252. It’s just a trick of the mathematics.
And brad_d, you’re a little off on your numbers. 1HP = 2546.4 BTU/hr.
Otherwise, I’d have to figure out a way to run my van with this 45,000 BTU/hr monstrosity, instead of the 460 that’s in it now! 
Slight hijack
I work for a euopean car company. We publish a pocket data book for technicians so that they can refer to size of things torque spec and other odds and ends. Being european they have always expressed everything in metric terms with US equivlants.
Seems in 1999 They gave this conversion task to someone who wasn’t too familar with the US
All the engine sizes were in liters with the US equivlant being QUARTS
Got quite a laugh around the office.
BTW our largest engine is the 3.0 quart engine…
Whoops. I read my ancient conversion table backwards. 
Never mind the slight error in the number therein. Thanks.