Brooklyn-427,
Thanks for the thought, but I have studs & nuts. I also checked tightness because I know the gaskets can relax a little from new. However, all nuts seemed snug. I guess I've been unlucky with this engine. Don't whether to try and bodge it with RTV as Large Arbor suggests and then live with it until I need to pull the engine again, or bite the bullet now after only 18 miles of running and pull the engine and try an re-seal the rear main cap seals.........sooooooo frustrating! I finally got to experience 600hp in a lightweight Kirkham and was blown away by the acceleration. All I want to do is drive the thing and enjoy it.........not blow
oil out of the back of the engine!