[356RS]

Hi Dave, Did you check to surface area on the case to make sure there was no rough spots? The seating area for the o-ring and special washer is often cleaned up by the machine shop when work is being done on the case to make sure the seating area is flat and smooth. All the o-rings are the same size for many 911's 356's and 914 cases and also use the same special washer. I did think there was any chamfer on the engine case, only on the washer. Did you use the o-rings that came with the gasket kit? If not that could be the problem.