Inside The No. 1 Qualifier

A Question Of Compression
JKRE built the engine to run 12.4:1 compression on 91-octane fuel in the competition. Sounds pretty high, even with the heat-dissipation qualities of the aluminum Tiger heads. "Yes, it may ping and rattle a little bit," Kaase says, "but the engine has more cam than you would normally run on the street, which reduces cranking compression somewhat to ward off detonation. We also welded up the combustion chambers and reworked them to reduce volume to just 37 cc to gain quench area on each side of combustion chamber to further avoid detonation. Piston-to-deck height is +0.010, and the piston top, though it has a large dish to reduce compression, is shaped to mimic the combustion-chamber shape to increase quench area. The valves were Calico heat coated on the intake to reduce the heating of the mixture entering the chamber and on the exhaust to keep the valve from glowing red, and providing another possible origin for detonation. Running 28 degrees timing with 23 degrees initial up to 4,000 rpm and then adding in the final 5 degrees also reduces detonation slightly, but backing off the timing too much can really hurt power."