390 strokers: 431 vs 445

[moore_rb]

Originally Posted by 120mm

Right now, the two most common stroker "kits" are 4.125 or 4.250 cranks, which result with approximately 431 or 445 c.i. displacement.

Knowing that, why would someone choose 431 over 445?

I'm new to stroked engines, so am curious as to what makes the smaller more attractive.

My (amateur engine builder) opinion is right in line with Blykin's (pro engine builder)'s opinions..,

and I also agree with Patrick that with a street engine, the "feel" and the sensation that an engine provides you is just as important as the raw bench-racing numbers, so focus on the shape of the HP and torque curves that will maximize power in the RPM ranges that your car will actually spend time operating in, moreso than worrying about peak numbers.

As to why someone might purposefully choose a same-priced, but smaller stroke crank... Mainly that choice is made when building an engine for a racing class that has specific cubic inch limitations, or maybe has cylinder head limitations (some classes require factory, unmodified head castings that reach a point where they just stop flowing any better, regardless of how many more CFM you try to pump through them)

but for a hobby-car engine, where cost is a concern- absolutely- take the free cubes wherever you can get them....

Nothing creates power easier than basic air-pumping capacity.