Hey guys,

I'm trying to diagnose a strange valve train noise in my truck. It is absolutely driving me crazy and I'm not sure where to go from here.

Its a turbo 4.8 with a small cam, comp beehive springs, ls7 lifters, Texas speed push rods, and comp trunion upgrade. All the valve train mods have about 5k on them.

About 8-10 min after I start it, I hear an RPM based ticking on the passenger bank of the engine. It lasts about 2-3 minutes and is RPM based. The truck doesn't miss out, but I haven't really beaten on it when this happens for obvious reasons. My wide band reads fine. After 2-3 minutes, it goes away, and doesn't come back until I turn of the truck and let it cool off. I've driven it over an hour after it happens with no additional noise.

I initially thought it was a lifter, so I pulled the heads, put a new set of lifters in and called it a day. Same damn noise once I started it up. When I took it apart, all of the valve train looked and felt fine. The only thing I didn't do was pull the springs off. I've also checked for an exhaust leak (I have a Trick turbo manifold) but didn't find anything. I also unplugged my injectors one at a time while it was making the noise and the noise didn't go away.

With that said, I'm ready to give up and buy either an L33 or Lq4 because that would fix it and be a lot more fun, but I really want to know whats going on as I was planning on reusing some of the valve train stuff since it only had 5k miles.

Any ideas? I'm at a loss. Thanks in advance!

 

Could it be piston slap or how about taking a mechanics stethoscope to the block while it warms up to pinpoint it better.

Otherwise I'd not even give a **** if the noise stops after a few minutes.

 

Thanks...I order a stethoscope and I’ll see what I can find. I’ve never heard piston slap, is that common on a stock engine? Mine has about 110k.

 

Yeah man! Super common. GM even had TSB’s about it. You don’t need a mechanics stethoscope if you have a super long screwdriver, it works just as well. I’m going to say there is an exhaust gasket leaking and when the motor warms up enough the “ticking” goes away. Either the o-ring gasket or manifold gasket is leaking. Could even be a loose bolt/popped manifold bolt head

If lifters we’re going to fail they would make noise 24/7

If a rocker lost bearings in the trunnion you would have seen material in the top of the head with
The valve cover off( you would also have a misfire, possible bent pushrod )

If a spring collapsed you would have hard starts, misfire, and other driveability issues

 

I’ll double check again for exhaust leaks. I kinda figured if it was anything else the noise wouldn’t come and go the way it does. Thanks again for the help!

 

Did you solve the issue?