Well I was told in school that a 1.71:1 rod/stroke ratio is the ideal ratio. The smaller the ratio, more stress is put on the side of the cylinder walls because the rod is trying to push the piston out of the side of the block. Anyone have any "ideal" numbers or anything. Any info would be appreciated

 

dude- search. This has been beaten to death.

lower rod/ratio has an impact on things such as side-loading forces and piston dwell as well as many other things.

 

Well if the search engine was working maybe Id attempt that.....

 

This is a good topic to discuss. In a "perfect" world, i thought 1.75 was the best ratio...

 

2005.2.19 (Night)

Uh, you might already know this, BUT, ANYWAYS----

Long stroke, Small bore = Torque, Low RPM (i.e. truck engine, Nissan KA24DE)

Short stroke, Large bore = Horsepower, High RPM (i.e. Champ car, Suzuki GSXR)

Equal Stroke to bore = you'd think a good balance between the two, but from what I heard it makes the engine "dull" in response. Kind of like riding one of those electric scooters up a hill....ugh.

Not much ratios going on here, but in general it works... and well, for us laymen, "in general" is best.

 

you want your rod to stroke ratio from 1.7-1.76. that is the ideal rod to stroke. like you can see above if you have the longer rod your dwell time is longer and you get more torque but you sacrifice rpm speed. short rods have more rod angularity and as you said wears the bottom of the cylinder walls but you gain rpm speed. as long as you stay between 1.7-1.76 you'll be alright. also it depends what you are building the car for, drag, autocross, etc.