Calculating rod length change effect on timing

I've been watching #5 take a beating on my hemi for a while now and figured it might be time to try a shorter rod...

I figure it could really do with one degree taken out on that cylinder and I've been trying to remember the maths behind it.

It a 4.467 x 4.150 stroke combo...

Is the maths as simple as 4.150 / 360 = 0.0115 ???

Thanks for the help

Russ

 

The piston will stroke 4.150 in 180 degrees of crank rotation.
Also near TDC the piston slows so the distance travelled decreases. Using the basic math you would come up with 0.022" per degree of crank rotation when in reality the piston would move around 0.041 for the last 10 degrees of crank rotation.

 

Rod length / timing

According to my trig. if we are using 25 degrees as a base line then one degree would be equal to 0.015" two degrees 0.030" three degrees 0.044".

Depends on where you start as said earlier the piston slows down the closer it gets to tdc.