Replaced intake manifold gasket, ran good for a day,then oil pressure started bouncing, overheated and shutdown. Had it towed home, Been sitting for 6 wks. Assuming oil pump screen was clogged from manifold change. Trying to access damages, but will not start, cranks but wont start. Any ideas where to start?

 

You need proper quantities and timing of Air, Fuel, and Spark to have a properly running engine. If you do not have all three, the engine will not run.

Now, why would you want to start an engine that you suspect has had oil starvation problems. You should be concentrating on preventing further damage. If you suspect that junk has gotten down into the oil pump screen and clogged it, then you might want to get the pan off and inspect the pickup.