283 Chevy small block

The ones that are off-put it back in place and tighten it while turning the push rod till push rod won't turn-not fire it up now tighten down the rockers til the noise stops and then 1 full turn do this on all of them. Loosen it till its start clattering and tighten it till noise stops and then 1 full turn-When done check ignition timing-

Check the rocker arm, push rod and the valve lifter

You need to remove the intake to get at it-You can pull the lifter out with a special tool-check tool rental

If this is a 1973 engine then it's more than likely your camshaft has worn down. These were famous for doing this. If your lifter tool won't get teh lifter out it may be mushroomed on the bottom and the only way it will come out is through the bottom. But you'll need to pull the cam out first as you'll need a new one.

You have to pull thedistributor to remove the intake. Eitehr mark the distirbutor and the rotor and don't turn the engine over. If you do turn it over, takeit to number 1 (left side front) with the timing mark on crank lined up to cam cover mark, point rotor to about 11:30 with 12:00 being front of engine. It should start ok then or it will be off a few degrees but easily reset.