L31 loose rocker arm

[andrewm]

97 k1500 crew cab L31 (Vortec 350), 240k miles

Over this weekend I changed the lower intake manifold gaskets due to the leaking gaskets, pretty straight forward. Truck has never given me trouble outside the fuel injectors clogging, which I replaced with the updated delphi system.

During the reassembly, about 98% done I'm putting the bank 2 valve cover back on and notice that one of the rocker arms is loose on cylinder #2. Crap. I didnt see anything unusual when I had the manifolds off, but I didnt really feel aroudn for anything.

Now, from what I've read the pushrods on the L31 are fairly weak, and usually bend/break before the valves do. I've not taken the L31 apart past the lower intake manifold, but I assume I will need a special service tool to remove the push rods, and I have to take the lower intake manifold off again...

She ticks when she's cold, but once warmed up it goes away. I have not yet set the timing with the PCM tool, but if I have to take the distributor out again, I don't see any point in taking it to a shop to set the timing just yet.

Barring a bent/broken push rod, the spring looked okay. So if the pushrod is solid and undamaged, I'd be looking at a bent, or burnt valve. Which the thought is just weighing me down.

Thoughts?

I can't access fullsizechevy at work, it's a blocked site...

[brent5631]

Can you not remove the offending rocker and pull the pushrod up from the top of the valvecover?
I know you can on a LS motor. And these are Hydro lifters so you cant necessarily say that it is loose when it has had time to leak down.

[andrewm]

You can, but I think the trick is more about the lifter coming off the seat and falling in. I remember that from somewhere, but I'm not 100% sure. I tried searching for the answer to that, but I'm not finding anything to support the answer.

The fact the tapping goes away after a warm up makes me think I have a collapsed lifter, to be honest. Might be that once the oil thins out it starts to get better. Not sure how I feel about that since the motors have notoriously weak push rods and typically outstanding lifters...

Edit, this is annoying me. I keep trying to double check my memory, but you're right. For the old school SBC you dont need to take the manifolds off, nor for the LS series. Why I remember this for the L31 I cannot fathom. That's what irks me, to remember one specific motor that you cant do it on? Just makes me think I remembered that for a reason!

Like the fuel pumps on 7.3l ford diesels, when you remove the fuel pump, hold the valve tight...

[brent5631]

The lifter sits right on the cam and is in its own bore so I don't think it can go anywhere when the pushrods are removed. I'd pull those pushrods and check them. If they are straight (roll the on a flat surface) then maybe the lifters need to be changed.
But Chevy motors are known to e "ticky" either lifters or piston slap.

[andrewm]

Yea, I'm gonna pull it this weekend I think - It doesnt sound like piston slap to me, it's much closer to the sound of bearing rattle/slop. Just not in the right spot. But you're right about Chevy motors are notorious for their ticking, especially in the cold.