Best overall SBF combo for a street/strip Cobra

[blykins]

By itself, the stroke doesn’t make the torque, it doesn’t shape the curve, it doesn’t control the rpm limits, it doesn’t control the smoothness. All of that is attributed to other parts of the engine. You could literally substitute any other number into that sentence and say the exact thing.

Do you think an engine with a 4.400” bore and a 3.25” stroke would behave the same way as an engine with a 3” bore and 3.25” stroke? Nope! It’s not about the stroke number!

[Streetwize]

Originally Posted by blykins

By itself, the stroke doesn’t make the torque, it doesn’t shape the curve, it doesn’t control the rpm limits, it doesn’t control the smoothness. All of that is attributed to other parts of the engine. You could literally substitute any other number into that sentence and say the exact thing.

Do you think an engine with a 4.400” bore and a 3.25” stroke would behave the same way as an engine with a 3” bore and 3.25” stroke? Nope! It’s not about the stroke number!

That’s not apples to apples so I’m not sure what point you’re trying to make

but there is definately a correlation between stroke and torque. Step on a 1 speed bicycle pedal, one with a 3.25 stroke and the other with a 4.25 stroke. The longer one gets going faster initially but the smaller one uses less energy to pedal faster once it gets moving.

Piston speed is also a factor…a shorter stroke will have less friction at any given rpm, and Peak torque is the RPK point at which ring and bearing Friction starts acting like a brake and overcoming the rate of acceleration under load. And that is generally why shorter stroke engines tend to carry more rpm between peak torque and peak hp RPM where long strokes tend to flatten out at a faster rate. All else being equal.

That’s true of any 4 cycle engine that have enough airflow and combustion efficiency to reach that point.

And with full respect….The whole point of this thread really wasn’t anything to do with engine theory, it had to do with what engine cubic inch combination might produce the best powerband might be in a 90” wheelbase Cobra.

[blykins]

I'm sorry, but a lot of the statements that you're making are just basic internet-based misapplications that I see on various forums. They are unfortunately passed around and around and are never corrected.

Let me try to be more apples to apples...

Displacement makes torque. Not the stroke. A 4.030"x3.250" engine is a 331. A 4.125"x3.250" engine is a 347. They will not have equal amounts of torque because the stroke is the same. You chose the 3.250" stroke because you stated that it's the 3.250" crankshaft that makes an engine docile, linear, predictable, non-violent, etc. I could build an engine exactly like that with a 4" stroke, or a 4.250" stroke. I could also build a 331 that would be more "violent" than your 427 and would make you poop your pants if one of your friends hopped in and did a 360 around a corner...

I understand that this thread is not about engine theory, but your fascination with a 3.250" stroke prompted me to explain that the stroke is not a magical number. It's the combination of *every* part that's in an engine that makes/breaks a combination.

Nice to see that I'm highly respected until I disagree.