I have a 94 ranger with over 300k. I recently tore down the motor to replace broke piston rings. I got it all back together it has a extremely loud screeching noise. Give it a little throttle and it goes away but comes back when you let off the gas ( no matter what speed). Ive removed the valve cover thinking a lobe on the cam was being destroyed but everything appears fine. When i had the head off all the valves were closed. After running it I did a compression tes and realized I had no compression in cylinder 3. So off came the head again. Come to find out someone intentionally put a bolt in my valve and had it wedged open. I removed the valve and took the bolt out. Inspected the valve and seat they both looked fine so I thought nothing of it and put it back together. I'm sure it isnt causing the noise. I know the sound of a bent valve or something wrong with the valve. Also I dont have ac or power steering. I removed the power steering thinking that was the problem, just a bad pump but no luck. Ive nearly replaced everything on this motor undoing the previous owners damage. Any suggestions are welcomed