Box Stock

Big bore or stroker

Problem with either is this.
A bigger bore means a heavier piston and seeing as how the engine is not in proper balance with the stock bore, you can imagine what it’s going to be with a bigger piston. Still, the crank can have more counter weight welded in and that would help.
A longer stroke means the rod is even farther away from ideal. Yes there is a longer rod and piston to go with it, but it’s still to short. No way to adjust for a rod that’s too short.
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.
 
Just my .02 but on this question I look to the nascar engine builders. When at the bigger track and they wanting more hp and being restricted to 358ci they go with big bore small stroke, now in turn at the short tracks when needing that torque coming out of the corner they go with less of a bore and a bigger stroke. Now of course they do a lot of different things to the heads.
 
My head builder has always told me more stroke for dirt oval and more piston for paved drag racing lol everytime I do what he says it works, go figure an old guy with wisdom lol
 
Clearly I see many of you have never had or ever ran a big bore gx200/clone. Or let alone run a stroker big bore.

The answers you guys are saying are way off
 
dwight80 said:
Just my .02 but on this question I look to the nascar engine builders. When at the bigger track and they wanting more hp and being restricted to 358ci they go with big bore small stroke, now in turn at the short tracks when needing that torque coming out of the corner they go with less of a bore and a bigger stroke. Now of course they do a lot of different things to the heads.
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in Europe, they make kart engines with both long stroke and short stroke. Both win, regardless of the track.
 
I was thinking if he is running s/a or open it would depend on having a big bore or stroker. As the 3inch really starves for what it needs with a little s/a carb as a small bore stroker would be a better choice. If he is running open, a 3inch with a nice big tilly or equivalent carb would be much better choice.
 
You are not going to find any winning difference in bore and stroke relationships.
Get yourself a proven good engine, and work on the kart/tires/driving skills.
Never mind the esoteric when working on karts.
 
PD Power said:
You are not going to find any winning difference in bore and stroke relationships.
Get yourself a proven good engine, and work on the kart/tires/driving skills.
Never mind the esoteric when working on karts.
Click to expand...

All the guys that's losing will beg to differ. When you have less power tires and kart seems to handle and drive much easier than someone with more power.
 
flattop1 said:
also with out doing any math typically you will gain more cc with stroke increases than with bore increases.
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The math says it's actually the exact opposite; an increase in bore will yield more displacement than the same increase in stroke.

4.00" bore x 3.00" stroke: (2.00²)(pi)(3.00) = 36.7ci (starting point)

4.00" bore x 3.50" stroke: (2.00²)(pi)(3.50) = 44.0ci ( + 0.50" stroke)

4.50" bore x 3.00" stroke: (2.25²)(pi)(3.00) = 47.7ci ( + 0.50" bore)

Freezeman said:
How is the displacement not going to change with either a longer stroke or bigger bore 65Shelbyclone?
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How could two otherwise identical engines have the same displacement, but different bore:stroke ratios?

astrowrench said:
My Point was simply speaking stroke produces more constant and a broader torque band starting at a much lower rpm and remains smooth and progressive as rpm increases;with out a doubt the V8 would produce more ultimate torque,but look at the torque and horsepower curves, the long stroke Flathead is much more consistent
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Consistent curves? What does that mean?

Again, the flathead doesn't belong here. We're comparing two engines of identical architecture.

alvin l nunley said:
Problem with either is this.
A bigger bore means a heavier piston and seeing as how the engine is not in proper balance with the stock bore, you can imagine what it’s going to be with a bigger piston. Still, the crank can have more counter weight welded in and that would help.
Click to expand...

A longer stroke is going to increase piston acceleration and the apparent mass of that piston as it applies to the dynamic engine balance, so I don't think one has a distinct advantage in that regard.
 
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