Best overall SBF combo for a street/strip Cobra

[Streetwize]

Brent,

Don't get me wrong I agree with your "go for cubes' and 600HP or more is great, but for MOST cobras even with 450 hp puts the power to weight ratio of a 1000cc Sport bike.

My whole thing is what (TO ME) would be the best overall motor combination for a Cobra.

the ~ 3.25" stroke in any small block, Ford, 327 Chevy, 340 Mopar is just a great balance of "just right" torque for a light car and it makes a very linear and predictable and very "fun to drive" power curve, which for I think a lot of people might be "just right". The torque stays flat and the power curve, even with a very docile and streetable cam, just goes up and to the right, all the way past 7000; so the HP gain per 500 rpm is not violent, like a "light switch" or a nitrous shot, but it is "predictable" and the part throttle roll-on makes the cobra feel more like a High torque 289 FIA car.

That's why I picked this combo around this stroke. It's not about the peak hp its about the drivability and fun...specific to a street driven (or even an occassional track day road race) Cobra.


I love the 427 Windsor in my Midstates cobra, to me it feels "perfect" with the 500/500 wall to wall torque and a Tremec and 3.50 gears. BTW my Rotating kit was the very first one Coast High Performance sold over the counter, with bushed 340 Mopar Rods that needed a good bit of rod shoulder massaging just to clear the cam lobes.

But when my friends all say "can I drive it?" I have to tell them "Hell No!" because as any of us know, most people cant jump into a 500hp 2500 pound car with big block torque at 2500RPM and then romp on it and not get sideways or do a 360 going around a corner.

Yeah my whole point of this thread was looking for the Cobra specific "ideal" 4.125 x 3.25 302 block 347 (Again, to me) would be a perfect all-around motor for a Cobra; combine the 289 tractability at part throttle along with the sports car 7500 redline, along with FE 427 S/C 500 ish HP power up top. So it's not the HP really, it's how you want to apply it, and that could be "tuned" simply by how you gear the transmission and rear axle.

Maybe not what everyone would build for themselves, but one that ANY Experienced Cobra driver could drive and be happy with and respect.

The thread was also to encourage what others what They think is the perfect combo.

[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.