I have a 2wd, 1997 Rodeo that makes a very load clanking noise. I have been told that it is the lifters however, I have done about everything, to fix it... Tried Reso, Heavyweight Oil ect and it still makes the nosie. 80k in milage, it started around 50k Could this be the timing belt. Also I am getting horrible milage around 9 mpg. Not sure if the two issues are related.

Loud knocking at idle or low RPM's is typically a worn timing belt tensioner assembly on these trucks. This will create enough slack in the timing belt to let it slap against one of the timing belt covers. Many have mistaken this for a rod knock. If you remove your T-belt covers & the noise stops, this is your problem.
G/luck
Joel

you said you ran heavy weight oil? you need to run a lighter weight like 5w30 mobil1 synthetic. my 97 has a tick and nothing has helped it either. some say lighter weight oils will help because the oil passages are blocked and a thinner oil will penetrate through. Although none of this applies if the t- belt tensioner is worn out. have you changed the t-belt yet?

I vote t-belt tensioner. The hydraulic pusher part is what is probably bad and the idler is clanging against it. Cost about $75.00 for the part.

idler? what do you mean cat fuzz

The idler is the pulley that pushes against the timing belt. The pusher is a little hydraulic piston that pushes on the idler instead of a regular spring like some other cars have.

so a loose tensioner can sound like a valve tap? is the noise similar to a valve tap, or do they sound different?

Yes. It's pretty loud though. With mine, it wasn't constant though. What happened is the little cylinder got stuck and had stopped pushing on the idler. Eventually the cylinder kept getting pushed back down into the bore and just stayed there instead of springing back out. The idler was banging against the cylinder which was making the noise.

mine gets louder and quieter, it fluctuates, have you heard anything about this? when you get a new tensioner does it include the hydraulic piston you were talking about?