oil priming on my 350

[matt h 350]

right firstly its a 4.2 v8 development stage 3 build,which i bought 2nd hand..it was still cellophane wrapped and untried,now ive tried to prime the oil pump,with vasoline and the dist drive tool,but i still cant get oil pressure...ive even cut the top off an old filter and watched the oil pump up,its full of tiny air bubbles..
any ideas
oil pressure shows 50lbs on the dash and then just falls away to zero plus warning lamp

[2mad]

hi you could try back filling the oil pump by getting a plastic tube on a
plastic bottle like the old casterol bottles and sqeezing the oil in the oil filter hole sqeeze for about 30 seconds then screw the oil filter back on the oil pressure should be restored if it is not then it could be a stuck oil pressure relief valve .