get out your DR. tools
Start the engine and start to listen to the noise, use a stefiscope[spelling] and move around to see where the noise is coming from. I had one that was something like what you are talking about, and it was the blower. Changed it out and the noise was gone. A rod knock will be it's loudest at morning startup's. That is when there is no oil to quiet it down.... They also sound more on the bottom of the engine. You can also use a long screwdriver to listen as well. Please be careful when you are putting the end of the driver on the engine. place the other end[the big end] to your ear and you will be suprised at all the things that you can hear...Good luck and if it is bad you can always sell it to me.........Rich
Too many cars,too little time to drive them. Anything less than 500 cubes is a small block. If you slow down in life you will get run over..