1995 Blazer 4.3 motor knock

I bought this blazer from my mother in law, it sat about 4 months during the winter. I went and picked it up and drove it for about a month and a half. I then changed my oil and the motor began to tick. It then became a knock, I tried a different oil filter, oil and tried mystery oil, and lucas. If its colder out it takes about 30 - 45 seconds before it starts to knock, what is the problem and why did this happen?

Is it in lower end or top end of engine?
Does it do it under a load or sitting still?
Can you change the noise by shorting out the cylinders?
How is the oil pressure doing?