A simple question which is nonetheless CONTROVERSIAL
 

I don't want to be the next person to ignite the BB-vs-sb firestorm BUTT, after reading tons of literature and talking with people about any number of engines, AND having driven my own 351C as well as several BB cobras---I have a question specifically about displacement and "real" horsepower (vs "pony-power").

The April "Mustang and Fords" issue had the article title "Still No Replacement for Displacement" which is a new twist on the old adage "There is no substitute for Cubic Inches". So, I talked to several local Ferraristi (a convenient source of low-displacement, high dynoed power afficianadoes) and then to some American big-block fans. The latter said, "unless each rated horsepower and foot/lb. of torque comes from close to a cubic inch, it won't have the grunt". In other words (let's say), 450 hp/450 ft/lbs. from 270 ci is NOT the equivalent of 450 square from 427 inches. I suppose this means that 1.8 hp @ cubic inch is not as powerful as 1.0 hp. One old, wise man said, "Rated (dynoed) hp is hp--period. It's the torque which does the talkin' and THAT'S where the cubic inches count!"

Who's right? Do you need the cubic inches to have real power, or do these frenetic turbo'd rice-burners have the answer (in equivalent power)? Is there, in other words, TRULY no substitue for cubic inches, or is it all in letting those cubic inchces breath? I tend to believe that displacement is the easiest and truest source....until some steroided Honda gallops past my cobra, that is.

Hope there are some brave and helpful piston-heads out there who'll throw their hats in the ring on this one.

Keep smilin'

There are four major things you must have to go fast/quick.
1. Horsepower
2. Torque
3. Drivetrain to hook-up and hold
4. Light weight

They are all equally important categories. You need them all whether you are drag racing, auto-crossing, track racing, or just trying dust off the car next to you on the street.

If you can get 450hp and 450 tq out of a small block, it is the SAME as getting it out of a ricer motor or a big block, but you will have weight differences.

True - to a point.

Getting lots of power from a small engine almost always requires that the small engine be revved higher and the power will come in a much peakier manner....in other words when that Honda jumps you you can be assured that he is in the right gear wheras with a large engine you may only have to jump on the accelerator to get going without the need for a downshift.

Torque IS what gets you there and torque is usually a by product of cubic inches (by the way I remember reading in Car and Driver about 20 years ago that when the torque is over 500ft/lbs it is spelled tork...FTF)



:)

Certainly no expert here but I think torque is overated in a light weight car. I know you need lots of torque to move 70,000 lb dump trucks but somehow the lightweight 4 cylinder rice burners with all the power adders can run in the 7 second range on the drag strip.
The high rpm F1 cars are very light and are the fastest accelerating road race cars and they have small displacement engines with little torque.
The Nascar stockcars of today are a little lighter than they used to be but run much smaller but more powerfull engines than they ever did.

Ain't nothing wrong with running one of thse big block engines in a Cobra if authenticity is your goal but for anybody to assume a big engine equates to better performance is fooling themselves and nobody else.

There is no replacement for light weight.

RD

As a fellow Cobra owner who also owns a turbo "rice burner" (Impreza STi- say what you will, then meet me on the AutoX course! :LOL: ), there's a lot to consider to the equation...
First off, while a smaller displacement engine is capable of big power, it has to work much harder to do it. Harder work= more stress.
While it is true our cars are lightweight- it's a relative thing; mebbe it's not needed in a 1300 lb Lotus or an F1 car, but torque is VERY important in a Cobra replica, IMHO.
A car w/ plenty of torque will be much more streetable than an equivalent car w/ the same hp, but lower lbs/ft.


Just my opinion- your mileage may vary,
Russ R

Indy cars don't need gobs of torque because they are already moving.....horsepower is what will keep you going.....if it were an acceleration race (like drag racing) it would be different. But Indy cars (F1 cars) just need top speed.

Torque is torque,

The tires don't know if it comes from a big block or a small block...

- Dan

Tannks, guys.....
 

I appreciate the input. I think you (sorta corporately) have explained it pretty well. I guess it has more to do with all factors combined. Nonetheless, the old goozer who is quite the local expert said that a 2.5 liter Ferrai engine rated at (let's say) 350 hp, etc. and and a 5.0 liter with identical stats----placed in identical cars (for the purposes of the argument) will perform differently. I told him that regardless of displacement, wouldn't they perform the same if their dyno numbers were the same? He said "Nope, cubes rule the roost, no mistake".

Scroot (Dutch verb)--I'm stroking the old Cleveland to 393 ci.!

Tanks again.

Fred - He's wrong. If two different engines have identical power and torque curves they will run exactly the same in the same car, PERIOD!!!! (as long as the engines weigh the same) Matters not if it's a Honda or a Hemi, high or low tech.
There is however intangables that make all the difference. Starting with costs, there is also durability factors, how a engine throttles up and down under load, V.E. factors that affect mileage, and how different engines react to heat to mention a few, and many, many other things.
In the real world it's these other intangables that dictate the choices we make with engines, or cars for that matter, or even toasters, blenders and t.v's.
Good luck with that 383,,,,,,,,,,,,,,,,,,
cobrashock

Freddy,
Don't listen to the old fart, probably hasn't been to a racetrack in years(if ever).
Just consider where the expert opinions come from. Usually guys who watch others perform are your best "experts". I find it ironic that the guys with the most "knowledge" can be found peering under the hoods at car shows.

If you wanna know how the wax your car ask Barry Maguire.
If you wanna know about performance ask the guys that still partisipate at the tracks.Better yet, do it yourself.

I don't care if your a BB or sb fan unless your involved your just guessing.

" I don't care if your a BB or sb fan unless your involved your just guessing."
AMEN BROTHER!!
Cobrashock

Same cubes does not equal same performance, in my opinion. Some engine designs "build rpm" faster than others. In addition to that other factors will come into play, like internal engine friction and weight of the rotating mass parts. Like pistons, crank, flywheel, etc. Alloy flywheel will "spin up" faster than iron wheel for instance.

Big Bore short stroke will accellerate to max rpm faster than small bore long stroke, cube for cube for instance. It's not surprising the 427 was a big bore short stroke as opposed to the 428 which relied on a longer stroke for more "torque" at a given engine speed. Porsche is famous for it's big bore short stroke approach to engine design.

7 second ricers and Formula One cars are hardly "real world" applications. But DO illustrate the holy grail of racing which is indeed "light weight" in every area.

1 pound shaved off "rotating"weight, like the flywheel or tire/wheels, is worth 3 pounds of static weight, like the drivers belly.

Maybe a way to visualize this is to think of horsepower as cfm in a tube.

Torque is the fan that pushes the air throught the tube. The larger diameter the fan, the biger the torque number (hp=tqxrpm/5250). A large fan or small fan can push the same cfm, but the small Ferrari fan has to spin faster to push the same cfm as the big block fan. Other things like crank/damper/flywheel weight will have an effect on perceived hp at the rear wheels, but if two engines have identical dyno sheets, they will perform similarly in a car.

You guys are great...
 

..thank you. I am absolutely sure old guru's wrong----but I have so much respect for age (having recently acquired quite a bit of it meself, ar-ar-ar), that I'm reluctant to lay the lumber on him. He was a decent race-driver and is the one who's teaching me to drive faster and safer. He is also a tremendous tweaker and tuner. I am more of a tuna (ar-ar-ar).

Tanks agin

Wanna prove him wrong? Take a nicely built 289 with a blower (for the torque) making the same power as a smogger 460 and see which is faster in the Cobra. My guess is the 460 will perform much like a 79 Trans Am, great power during parking manouvers but a slug beyond highway speeds. It'd feel more like a diesel truck than a sports car in comparison to the 289.

The difference is the power bands are vastly different. A 450 hp small block makes 450 hp over a very narrow range you may never see in daily driving, say 5700 rpm...

The 427, 428, 454 et al. will make 450 hp at 3600 rpm and can be made to scream well past 7,000....

So sure you can build a small block to make the numbers you want but you'll be wringing the @#$%^ out of it to get there.