Valvetrain noise when at operating temperature

[CJChen]

I have a 2002 Wrangler 4.0 off of a fresh rebuild. The engine sounds healthy and runs great, however, it has a valvetrain noise that only appears once the engine is hot. It can start and Idle for 20 minutes with no issue, but as soon as I drive it for a bit I can hear it when parking. It sounds like a typewriter and the "tick-tick" increases with rpm but the volume does not increase. It also can be drowned out around ~1500-2000 rpm. I feel like I have narrowed it down to two options: either I need to verify I have the right pushrod length (I used stock length pushrods) or it is a cracked exhaust manifold. If anyone else has dealt with this please let me know!

Pushrods: I took the engine to the machine shop and he took a minuscule amount off the head and engine. I am also using a slightly thicker felpro head gasket. I installed some Harland sharp non-adjustable roller rockers as well. I know that they tend to be a bit noisy, but I would imagine the ticking would be present the entire time if that were the case. Would incorrect-length pushrods be making this noise after warm-up?

Exhaust Manifold: I have dealt with exhaust leaks before, but usually that only applies on startup. They are the original manifolds, however it's difficult to tell where the ticking is coming from. it sounds like it's coming from under the valve cover but I haven't been able to narrow it down.

Long story not so short, is there any recommendations for how to narrow down the source of the tick?

 

[macleanflood]

Have you run the engine without the valve cover off and watched, listened and probed with a stethoscope?

-Mac

 

[Unique Username]

Sounds like most 4.0 engines I have heard run. Don't want to tell you it's completely normal as I have not heard it.
Many of the older techs used to say a tappy engine is a happy engine when it came to the old style flat tappet engines.

 

[CharlesHS]

One of the lifters may not be staying full pumped up when it warms up causing the ticking sound.
I agree with Mac that you should remove the valve cover after the engine has warmed up (very hot) to do an inspection for pushrod(s) that are loose or a roller rocker that has a problem.
The 4.0L engines run hydraulic lifters so valve adjustment is a non issue.

 

[gasiorv]

Are you sure it is the valve train and not the cam position sensor / camshaft synchronizer ? Usually a tick that happens when it warms up and at low RPM/idle which goes away when RPM increases. It is on passenger side right in front of the oil filter, when you hear the ticking if it is the Cam synchronizer you can feel it if you put your finger on the top of the sensor. I am not saying it is the noise you are hearing, but it is worth a check.

I think 2000-2004 4.0L uses the camshaft synchronizer (aka as oil driven pump assembly) and it has the cam position sensor mounted directly to the top with the wire connector pointing backwards. Not to be confused with the OPDA issue that the 05-06 experiences, but very similar.