this is pretty interesting, a stroker crank i would imagine the journal could be taken +.045" outward, used with +.050 undersize bearings, and therefore increasing stroke by ... i dont know how much.

Mark, do you know how to calculate how much this would increase displacement on a stock 1.8 block?

 

Roughly 1mm in stroke... although with the smaller of the honda rods I believe that as much as a 3mm stroke increase could be had. Using the 1.771 Big End Rod would mean that the normally 1.889 big end could be resized by as much as 0.118" (roughly 3mm), this would mean that the offset ground on the crank could be as much as 3mm. If you were to use a 1mm undersized bearing, you could theoretically get a 4mm stroker out of this setup. However you'll probably have to move the wrist pin quite a bit to accomplish this.

The miata already has a shallow 1.108" compression height to the pin, The D16 Honda has a compression height of 1.181", so that 0.080" and the 5 mm longer honda rod all of sudden can cause issues. 8mm is roughly 0.320" reducing the compression height from 1.108" to 0.782" This puts the wrist pin into the ring lands, or damn close to it. There are solutions to this problem, but they are not really "inexpensive". It doesn't have to break the bank either, just requires some clever machine work.

Mark

PS - The Honda Rods are available in lengths from 5.290" - 5.485", the stock miata rod is 5.232", so keeping the shorter rod and keeping the compression height reasonable is still possible.

 

Bruce, you know you're my hero. No need to flaunt it.