Intermittent Oil Pressure

Before I pulled the 170 out of Vixen late last year, she would so similar. Sometimes she would knock on startup both cold or hot. The oil light would stay on extended periods....like ten full seconds, then go out and the engine got quiet. Sometimes it didn't do it. Never once though, did it lose oil pressure once running.

I suspected sludge in the oil pickup and I was sorta right. After I pulled it and got the pan off, there was a layer of sludge about a full 1/2" deep, with the exception of a round disc directly under the pickup. There was actually little sludge in the pickup itself.

Although the bearings were still in fine shape, since I had new standard rod and main bearings, I replaced them, along with a new oil pump, oil pickup and timing set. Now it turns the oil light with the starter before the engine ever fires, even after sitting long periods.

You got something going on affecting the supply of oil "somewhere", "somehow". When you had it all down, did you think to look at the block where the pickup screws in? I hate to say it, but I have seen a big block crack where the pickup screws in and they are very similar. When it got hot, the crack would open up and the oil pressure would drop. The guy took it to several shops and nobody could find it. He was a friend of mine so I told him to let me have a swing at it and I found it. He actually had another engine and we opted to go that way.