The +.003 Over Piston fits the 196cc blocks when honed.
This piston allows you to make minor bore corrections and prefer crosshatching and surface finish for your blueprinted 196cc clone box stock racing engine. The benefit of the .003 vs. .005, .010, or larger bores is minimal additional weight while potentially better ring seal from honing resulting in more power.
Piston Specs
- 2.678" (+.003" Over Stock)
-Compression Height .9235" ± .005
- Dish Top
AKRA 2020 Rules for Piston & Rings
The piston must be unaltered box stock only. Overall piston length 1.935" max, 1.920" min and from top of wrist pin to the top of piston .580" max. The arrow on top of the piston must be pointed towards valves/lifters. Overall length wrist pin 2.100" min, inside diameter .550" max. Top ring and middle ring .115" max-width, .060" max thickness.) Filing of ring end gaps permitted including oil expander, max end gap .040" (top rings only.) The lapping of rings permitted for proper seal. Piston Ring must be on the piece (unbroken) when presented for tech. Piston Rings must be self-supporting in the cylinder bore when checked installed on the piston with a connecting rod attached (rod cap and bolts installed are not required for this check). Minimum weight of piston 145 grams. Honing of wrist pin journals permitted. The bore surface must remain flat and retain stock configuration edges. The skirt of the piston must retain as produced no chamfering, radius, or breaking of edges permitted. Up to .010" over piston allowed
NKA 2020 Rules for Piston & Rings
40.4.12: Piston
40.4.12.1: Must be of a three-ring design.
40.4.12.2: Minimum weight of 145 grams with Oil Expander Ring and two rail
rings installed.
40.4.12.3: Piston length is 1.935" max, 1.910" minimum. .580" max top of
wrist pin hole to top of the piston as measured with a dial caliper.
40.4.12.4: Standard bore is 2.685", maximum overbore allowed is 2.700".
40.4.12.5: The piston is not allowed to be any higher than the deck of the block
at TDC, zero tolerance (zero deck height).
40.4.12.6: No flat top piston allowed; must be dished-OEM w/no modifications.
40.4.12.7: Aftermarket pistons and/or sizes up to .25mm (0.010") over are
permitted.
40.4.12.8: Machining of the piston is prohibited.
40.4.13: Piston Rings
40.4.13.1: It is mandatory that all three rings be intact and functional.
40.4.13.2: Top ring must be the chrome face ring
40.4.13.3: No alterations of rings are permitted.
40.4.13.4: Ring Sizes
-Top Ring
.058" +/-.005" height & .115" maximum width.
-Middle Ring
.058" +/-.005" height & .115" maximum width.
- Oil Expander Ring (reference)
.095" +/-.005" height & .092" +/-.005" width
40.4.14: Ring Tension Requirement
- Top two rings must support themselves in the cylinder when removed from the piston. They cannot fall through the cylinder.
- The bottom ring is a non-tech item regarding tension. The bottom expander ring & two rail rings, when mounted on piston and rod in place, should support piston in
the cylinder when inserted upside-down.
40.4.15: Ring Tension Inspection Procedure
- Top 2 rings must support themselves without assistance in the cylinder.
- Each of the top two rings should be placed, individually, approx. one inch
(1") down in the cylinder.
- Square ring with piston turned upside down.
- If the ring supports itself, it is legal.
