A head gasket instrumented with ionization probes made using printed-circuit-board technology has been successfully demonstrated in a single-cylinder development version of a General Motors 3800 V-6 engine. Four different gasket designs were tested, but common to all was the use of a printed-circuit-board layer to provide multiple ionization-probes around the perimeter of the cylinder bore. The probes detect the arrival time of the flame at eight equally-spaced locations, giving an inferred measure of flame geometry. The cylinder pressure is recorded simultaneously with the eight ionization-probe signals using a personal-computer based data acquisition system. The technique provides a useful tool for studying cycle-to-cycle and cylinder-to-cylinder variations in the combustion rate as related to the flame arrival time at the gasket face. The design features of the gaskets that both succeeded and failed are discussed, and representative ionization-probe signals and data sets are presented.