I have a 1989 Chevy Caprice with a small block 350. I'm not sure what all I have in this motor, but i'm going to try and explain this the best. My motor was rebuilt last year and recently I started hearing this knocking noise. The noise does not start until the motor warms up or gets hot. Someone told me that it may be the cam. Somone else said it may me a lifter, or a roller rocker. The noise is just coming from one side. One mechanic is telling me that its going to cost me $1200 to get fixed. Its hard to find a good mechanic. Can i get some help or ideas???????

How is oil pressure?

its a lifter not getting enough oil pumped to it i think, or a bent valve