valvetrain ticking

[Rippin]

Recently I've started getting a pretty loud tick coming from the valve train. Seems to be coming from the rear of the engine. I haven't taken the valve cover off yet, but from what i can tell from the pictures I've seen there aren't adjusting screws on the rockers. how do they adjust?

 

[CJim7]

First (and always the first) thing to check when this phenomenon occurs is the exhaust manifold. You are looking for a leak whether it's a bad gasket or a loose bolt.
A leaky exhaust manifold will make the engine sound like it's coming apart.

If everything looks sound (see what I did there? ), it's time to pull the valve cover and start inspecting the valvetrain. loose, warn, or non-oiled parts.

 

[Rippin]

already checked the manifold, did that today. Gonna pull the valve cover next weekend, just not 100% sure what I'm looking for

 

[CJim7]

Recently I've started getting a pretty loud tick coming from the valve train. Seems to be coming from the rear of the engine. I haven't taken the valve cover off yet, but from what i can tell from the pictures I've seen there aren't adjusting screws on the rockers. how do they adjust?

The AMC 258 i6 / 4.2l uses non adjustable rockers. They are simply bolted down to the mounting bosses.

 

[CJim7]

already checked the manifold, did that today. Gonna pull the valve cover next weekend, just not 100% sure what I'm looking for

I always start looking to see if anything is loose first. Start poking around and if something feels loose, verify the rocker pivot bolts are tight. From there, pull them and check three areas for wear: the pivot cup where the pushrod rides, the other end that contacts the valve stem, and the area where the rocker pivots ride against the rocker. Generally if these areas are wearing, it's due to lack of oiling from the lifters via the pushrods...or..they are just getting old.

Verify that the pushrod is not plugged (you can see right through them). if the pushrod is not plugged, and it is not oiling, then it is a lifter issue, whether collapsed, plugged, or mechanical failure.

You can also verify valvetrain oiling by turning the engine over by hand or ignition (I prefer by hand) and visually observing oil at each rocker. This can actually tell you more then trying to guess if you are getting oil to the top end of the engine.

 

[73CJ]

4.2s have hydraulic lifters. Not adjustable.

CJim7 has good advise about cranking over without spark plugs and watching the rockers oil flow with the valve cover off.

Combination of high miles, dirty oil and/or low oil pump pressure, they will tick. Not sure how loud is "pretty loud" is. Chances are good you're looking at new lifters.

Alll this under the premise that no one has done a push rod or head swap recently.