Oil Filter Adapter

My bolt did not have either a gasket or copper washer, but appeared to be leaking mostly from the large gasket. Thanks for the source on the copper washer.

This gasket thickness thing has got me curious, so I did some measuring on a 340 block and the oil filter adapter. On the oil filter adapter, the inner (small) gasket machined face is 0.264 lower than the outer (large) gasket machined face. On the block, the inner face is 0.175 higher than the outer face. This means that when assembled, the compressed inner gasket should be 0.264-0.175=0.089 thicker than the compressed outer gasket.

It will be interesting to see the difference in new gasket thickness when my gasket kit arrives.