Quote:
Originally Posted by Streetwize
When you say "Again, do you think that a 4.250" x 3.250" combination would behave the same as a 4.000" x 3.250" combination".
Like me (or anyone with any sense) would think an extra 40 cubic inches would make any difference at all?
That sounds a bit condescending, but maybe you missed the "all else being equal" part...Like displacement, static compression ratio, etc
I only spoke in generalities about stroke. It's physics and trigonometry, not much to argue about. But Can you tune each one to Optimize each combo? Of course.
"Again"...I never said any of the other elements of engine design were not important for power production...but it seems like you want to harp on one thing I did say and maybe making it seem (to others) like that's the entire point of my thread?
I'll leave it at that.
But what about the question about loading up the 2 same displacement (1 long stroke one short stroke, all else the same) motors at 2000 rpm instead of 3000?
And again, I listed type of motor and powerband I (PERSONALLY) would like for my next Cobra....and back in the 60's there were certain factory bore stoke combinations (like the ones I mentioned, 327 Chevy, 340 Mopar), and with close ratio manual transmissions, they all have similar powerband characteristics as to how they put down power....and coincidently(?) they all just happened to all had a ~3.25"-ish stroke....and that's the kind of "linear" power curve I'd like to emulate in my next Cobra, only I just want to turn up the wick a bit.
Anybody who builds a motor either wants to (or settles for) a particular short block size / combo, this is the one I want to build.
The point of the thread was to ask what everybody else's Best Cobra combo is....and why they like it.
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If you want to change your argument now after thinking about it more, that's fine. But in your first several posts, you were very adamant about using a 3.250" stroke because (in your own words) "it's a great balance of 'just right' torque and a predictable power curve", along with saying that there is a correlation between torque and stroke.
Those arguments, along with a few more, are what I zoned in on because I see those incorrect applications being made almost on every engine/car forum.
There is no correlation between stroke and torque.
A particular stroke number does not (by itself) change any balance between torque and power curves.
We do not pull engines down to 2000 rpm on the dyno with a full load. It's very hard on an engine to do that and exposes them to detonation. It's also not necessary to do because higher rpm ranges give you a great view of torque and horsepower curves.
But no, I do not agree with your argument that the longer stroke engine "will accelerate harder because it generates intake velocity sooner". Getting the intake charge started sooner is not the job of the crankshaft stroke! It's the job of everything above it!
Again, you are so hyper-focused on a stroke number, and the stroke number isn't as important as what you're wanting it to be.