Going from the 948 to the 998 +.020" should be fine.  The 948cc piston is 2.4775", the 998cc pistons are 2.5420" and 998cc +.020 =2.562". The rods are the same, the pin height for both pistons is the same (1.342").

The change represents taking a 948 block and boring it +.0845" over (from standard).

We would suggest getting larger valves in the head to take advantage of the larger displacement. If you could find a 12G206 or 12G295 head - those have larger intake valves - or just go to the large intake valves in your head. That plus more of a street camshaft and maybe a header and exhaust and you'd be good to go.

Spridget Mania Tech Team

The Spridget Parts and Accessories Experts