"stroker" stroke doesnt add up

[mini64]

Can someone explain what I am missing here? I am looking at the Bean catalog at the stroker pistons made to allow a crossflow crank in a standard height twin cam block. The compression height of the stroker pistons is 1.46", vs 1.53 standard twin cam. Thats a difference of 0.07". But the stroke on a crossflow crank is 3.06", vs 2.86" on a twin cam. That's a difference of .2". So it seems the pistons would stand way proud of the block deck. Not only that, the crown on the stroker piston is taller too.

As an aside, as long as the crank width matches the rod width, does it matter whether we use the narrow or wide rod journal? I see BDD and such engines use the narrow.

[rgh0]

The extra height the piston comes up is half the extra stroke ( the other half is down the bottom of the cylinder. The increase of 30 thou that results is to close up the standard below top deck position of the piston to help achieve a higher compression I presume.

You need to check actual deck height for the block you are going to use to ensure it all comes together OK and potentially you may need to take a little off the top of the piston to get the clearances and compression ratio you want.

regards
Rohan

[mini64]

thats what it was - i wasnt dividing the stroke length in two when making my calculations- thanks!