A few questions and some things to check:
- What engine do you have and how well maintained is it?
- Check the oil level & quality as well as the coolant level & quality.
- Can you try and locate the basic area that the noise is coming from? Top, middle or bottom? Left side, right side, front or back? Use a mechanic's stethoscope to listen, or if you don't have one, a long handled screwdriver with your ear pressed against the handle and the tip held at different points around the engine.
Top end noises can be valve train, valve springs, rocker arms or hydraulic lash adjusters.
Middle engine noises can be piston slap or wrist pins.
Bottom noises can be bearings, connecting rods or the crankshaft.
Front noises could be accessories, belts, water pump, or timing chain.
Rear noises could be flex plate to transmission.
Hope this helps,
BILL