I have to adjust the rockers on my chevy 305 engine. How do I go about doing that?? They seem very loose.

Loosen one till it starts to clack. Tighten slowly till it goes away. Turn 1/2 turn. Repeat for remainder.

by the way, how bad does the oil splash around when you're doing this procedure, since the valve covers are removed and stuff lol... does the fact that the engine is idling really keep much from splashing everywhere

Thanks for the info. I wasn't sure if I was going to have to do each one at top dead center or anything like that. If its just as simple as tightening them one by one, I can handle that no problem.

by the way, how bad does the oil splash around when you're doing this procedure, since the valve covers are removed and stuff lol... does the fact that the engine is idling really keep much from splashing everywhere

Back when I worked in a shop, I bought these clips that clip onto the rocker arm to keep oil from squirting all over the place. Some oil will leak onto the manifolds.

This is a good article on adjusting valves without starting the engine: http://chevyhiperformance.com/techarticles/148_0303_valve/

//2000CAYukon

Here's how i do it without the engine running. get the cylinder to tdc. or when the valves are fully closed. Grab the pushrod with your fingers and tighten the rocker until it doesn't spin freely. Don't try and spin it real hard, it should not turn under some light pressure, then give it a 1/8 to 1/4 turn more.
You want to preload the lifter about .050 max. from zero lash.