427 Oil Leak Mystery

[Paul Sutphen]

My friend (Dave) and I worked all day on his Cobra chasing a mystery oil leak. Oil in significant quantity (enough to leave a 3" spill on floor after 15 min. run) is leaking at the joint where the Lakewood housing plate and the block where the pan is, come together, just in front of the oil pan flange. We changed the main rear seal (both circular seal and vertical seals), removed the tranny and flywheel, replaced a suspected leaking oil plug in the back of the block, replaced the oil pan and gaskets too! We didn't find much if any oil on back of engine block behind flywheel although the clutch housing had been soaked with oil as a result of the oil leaking down the plate and into the holes in the front of the lakewood plate. We changed the clutch pressure plate. We reassembled thinking we had covered all the bases, test ran with car on lift, and about 2 minutes after starting engine, oil resumed leaking - just as heavy as before. There are no oil leaks up above around valve covers and manifold joint. No oil is leaking into clutch housing as we taped off the holes in the Lakewood bell housing. We are now suspecting a cracked rear main bearing cap that leaks toward the rear between the bell housing plate or something else very unusual. Before we drop the pan again, do you have any suggestions?

Paul Sutphen and Dave Betts