then why does the article state this: "If you buy a big-inch engine today that will satisfy your need for speed far into the future, racing will be a more successful and more satisfying pursuit." and "A large-displacement engine makes a race car easier to run, simpler to maintain, and more consistent to drive. Cubic inches can compensate for a converter that's not quite perfect or a car that's a few pounds too heavy. If you are racing on a four-tenths Tree, the torque of a big motor will move the car harder on the initial hit of the throttle, breaking the beams quicker and cutting your reaction time. That all adds up to more round wins. Big-inch engines can also be less expensive in the long run." also "The price of power in a 358ci Pro Stock Truck engine is roughly $111 per horsepower; in one of our Super Series 565ci big-blocks, each horsepower costs less than $24. The bottom line: You get a lot more bang for your buck with a big motor!" oooh yeah and this "The simple fact is that big bores produce "free" horsepower."

need i continue?????????????????????????????????????????? ???????????????



check this out: http://www.musclemustangfastfords.co...est/index.html

for some reason the 5.4 seems to work just fine

 

Recently I’ve had several conversations with racers who wanted to build engines with long crankshaft strokes and small cylinder bores. When I questioned them about their preference for long-stroke/small-bore engines, the common answer was that this combination makes more torque. Unfortunately that assertion doesn’t match up with my experience in building drag racing engines.

My subject is racing engines, not street motors, so I’m not concerned with torque at 2,000 rpm. In my view, if you are building an engine for maximum output at a specific displacement, such as a Comp eliminator motor, then the bores should be as big as possible and the stroke as short as possible. If you’re building an engine that’s not restricted in size, such as a heads-up Super eliminator or Quick 16 motor, then big bores are an absolute performance bargain.

I know that there are drag racers who are successful with small-bore/long-stroke engines. And I know that countless magazine articles have been written about “torque monster” motors. But before readers fire off angry e-mails to National DRAGSTER about Reher’s rantings on the back page, allow me to explain my observations on the bore vs. stroke debate.

In mechanical terms, the definition of torque is the force acting on an object that causes that object to rotate. In an internal combustion engine, the pressure produced by expanding gases acts through the pistons and connecting rods to push against the crankshaft, producing torque. The mechanical leverage is greatest at the point when the connecting rod is perpendicular to its respective crank throw; depending on the geometry of the crank, piston and rod, this typically occurs when the piston is about 80 degrees after top dead center (ATDC).
So if torque is what accelerates a race car, why don’t we use engines with 2-inch diameter cylinder bores and 6-inch long crankshaft strokes? Obviously there are other factors involved.

The first consideration is that the cylinder pressure produced by the expanding gases reaches its peak shortly after combustion begins, when the volume above the piston is still relatively small and the lever arm created by the piston, rod and crank pin is an acute angle of less than 90 degrees. Peak cylinder pressure occurs at approximately 30 degrees ATDC, and drops dramatically by the time that the rod has its maximum leverage against the crank arm. Consequently the mechanical torque advantage of a long stroke is significantly diminished by the reduced force that’s pushing against the piston when the leverage of a long crankshaft stroke is greatest.

 

An engine produces peak torque at the rpm where it is most efficient. Efficiency is the result of many factors, including airflow, combustion, and parasitic losses such as friction and windage. Comparing two engines with the same displacement, a long-stroke/small-bore combination is simply less efficient than a short-stroke/big-bore combination on several counts.

Big bores promote better breathing. If you compare cylinder head airflow on a small-bore test fixture and on a large-bore fixture, the bigger bore will almost invariably improve airflow due to less valve shrouding. If the goal is maximum performance, the larger bore diameter allows the installation of larger valves, which further improve power.

A short crankshaft stroke reduces parasitic losses. Ring drag is the major source of internal friction. With a shorter stroke, the pistons don’t travel as far with every revolution. The crankshaft assembly also rotates in a smaller arc so the windage is reduced. In a wet-sump engine, a shorter stroke also cuts down on oil pressure problems caused by windage and oil aeration.
The big-block Chevrolet V-8 is an example of an engine that responds positively to increases in bore diameter. The GM engineers who designed the big-block knew that its splayed valves needed room to breath; that’s why the factory machined notches in the tops of the cylinder bores on high-performance blocks. When Chevy went Can-Am racing back in the ’60s, special blocks were produced with 4.440-inch bores instead of the standard 4.250-inch diameter cylinders. There’s been a steady progression in bore diameters ever since. We’re now using 4.700-inch bores in NHRA Pro Stock, and even bigger bores in unrestricted engines.

Racers are no longer limited to production castings and the relatively small cylinder bore diameters that they dictated. Today’s aftermarket blocks are manufactured with better materials and thicker cylinder walls that make big-bore engines affordable and reliable. A sportsman drag racer can enjoy the benefits of big cylinder bores at no extra cost: a set of pistons for 4.500-inch, 4.600-inch or 4.625-inch cylinders cost virtually the same. For my money, the bigger bore is a bargain. The customer not only gets more cubic inches for the same price, but also gets better performance because the larger bores improve airflow. A big-bore engine delivers more bang for the buck.

Big bores aren’t just for big-blocks. Many aftermarket Chevy small-block V-8s now have siamesed cylinder walls that will easily accommodate 4.185-inch cylinder bores. There’s simply no reason to build a 383-cubic-inch small-block with a 4-inch bore block when you can have a 406 or 412-cubic-inch small-block for about the same money.

There are much more cost-effective ways to tailor an engine’s torque curve than to use a long stroke crank and small bore block. The intake manifold, cylinder head runner volume, and camshaft timing all have a much more significant impact on the torque curve than the stroke – and are much easier and less expensive to change.

 

a long stroke small bore generates more frictional loss and more stroke that has no power pushing it down anymore meaning the next cylnder to fire has to work harder to pull the one before it down and back up again. shorter stroke is better. read my article. i posted the wrong link the first time.

 

We will see. IF it makes it to production, it will be watered down, or over priced. Ford dropped the ball on performance, as far as I am concerned. They cannot compete N/A, and have not been able to since going to the modular motors.

I hope it changes, but so far, I have not seen any indication it is going to. I loved making 475RWHP in my '03 Cobra, but I would rather make that, or more, on motor alone. Ford does not have anything available that can do it, unfortunately.

 

yeh its saddening but true. u can go onto the ford motor sports site and buy the 5.0 cammer as of now. and it isnt watered down. but damn they are expensive

 

Faster,

Did you really understand what you copied from this article

http://findarticles.com/p/articles/m...9/ai_n15614621

JMC

EDIT: spelling

 

Yeah nice cut and paste job. Next time reference your source. We knew it wasn't from you.

 

here ill quote myself to show i posted the link to the article but to save a click on your behalf i decided i would copy n paste it.

 

yes did you? longer stroke means less effective use of displacement for generating power. due to friction and windage and the factor of power through the length of the stroke did you understand everything in the article i copied for you?

 

Quoted from your source: Big bores promote better breathing. If you compare cylinder head airflow on a small-bore test fixture and on a large-bore fixture, the bigger bore will almost invariably improve airflow due to less valve shrouding. If the goal is maximum performance, the larger bore diameter allows the installation of larger valves, which further improve power.
The bore spacing on both the 4.6 and 5.4 engine are identical. There is not much more room to bore out the cylinder before you run into problems. That is why Ford decided to use a longer stroke in lieu of bigger bores. We can shoot the shìt and talk theory all you want but your article was not printed in reference to an engine that has the characteristics of the modular engine. Why does the 5.4 with identical cams and head make more power an torque than the 4.6? And to answer your question, no, I did not understand anything at all in your article......

JMC

 

I think anyone who is using a 5.4 or a 6.8 on the street IS concerned about torque at 2,000 rpm.

It's really nice to know that drag racers custom building Chevies can get more bang for their buck with a big bore vs. a long stroke. Can you let us know why that would be of interest to Ford truck owners? Or explain how it proves that an oversquare engine is superior to a long stroke engine for every possible application?

 

that reference was to show does the engine make low end power or top end power. one for speed and acceleration and one was designed for pulling.

 

its makes more torque but not HP and i have proven that. so has ford with the new 3v motors. and the 4v's and the 2v the 4.6 made more HP but less torque

 

faster150 makes me laugh sooo hard!