Did you prime the engine at all, sounds to me that if you did prime the motor and you did the biuld that maybe one of your galley plugs worked ther way loose and is leaking , witch is not comon at all but i have seen it happen,I think that your bearing clearances are very loose ( cam, rod ,crank and maybe even lifter bore) High oil preasure robs horsepower but a small chevy will be safe at 10 psi for every 1000 rpm's, some guys don't like to hear that but it's true,I have a 600 hp 383 that idols at 800 rpm.s and 15 psi and it sreams!! but to get this preasure i installed a soft spring in my pump. I hope you solve your problum before it's to late ! GOOD LUCK