onsdag 9 april 2014

Piston clearance for the 69,5 mm WW crank

So, at assembly it was clear that the my stock pistons from early 1957 did not fit as-is. At first I did modify the pistons according to Okrasa drawings from the 50's (thanks Bengt) but it still wouldn't clear the counterweights of the WW crank (early Okrasa cranks did not have CW).

In the end I did chose to do the Okrasa modification as well as shaving off 4 mm at the bottom of the skirt. Above you see a simpel sketch of what I did. I have included the distance from the piston pin center just so you can double check if you have some high-compression or stroker aftermarket pistons. In the end it's the pin position that determine what you need to do with the skirt.

Disclaimer: This is how I have done it. At this point in time the engine is only dry mounted and not started. This can act as a guide for others, but you need to think, measure and take responsibility yourself.

2 kommentarer:

  1. Hva er vekten på stemplene før og etter modifikasjonen?

    Mvh Kjell Roar

    1. I'll weigh them and post it on the blogg. Give it a week.