Recently I had to replace the valve cover gasket and at the same time took a look at restoring valve lash to factory spec of 0.012 for exhaust and 0.008 for intake. Most of the clearances needed to be increased a mil or two and the result was an engine that ticks quite a bit more loudly. When looking into this, actually reducing valve lash seems to have a positive effect on engine wear, fuel economy and also noise produced. As a result, I plan to go back in and change the clearances to 0.011 and 0.007 respectively. In this round of maintenance, it occurred to me I have a chance of inspecting the timing chain. At what point does the chain or anything related to it need service? Is there a way of visually inspecting its condition?

 

An irregular rattle at idle that improves as rpm's are raised is one clue. the other is if a plastic timing chain guide is broken. The one single reason why I favor plastic guides over metal.

 

Forgot to mention this 2.4L '94 22re is approaching 250,000 miles and ask at what point timing chains are usually replaced?

 

250k is a lot. But the question might be what was the mileage it was last replaced.
But hard to say mileage-wise. Proper oil changing with a decent filter with anti-drain back does prolong their life.
But one thing we saw often was headgaskets and timing chains having fairly similar lives. This is one of the reasons I encourage people to remove the head when doing a timing chain. It’s not hardly anymore labor, you can do a MUCH better job, and you don’t have to fret about the headgasket going out in the next year.

 

I doubt the head gasket has ever been replaced / I am the second owner since 130k. I would rather not get into servicing the chain / head gasket, but would like to preempt any damage due to chain failure.

 

servicing the head gasket and timing chain on the 22re is cake. i do it in my driveway. takes the good part of about 5.5 hrs to complete the job, but i've done it a few times.

jimkola is right, at 250k, if neither has been changed, you should at least be considering it. the 22re is an interference motor, but when the chain breaks, it doesn't always result in piston & valve contact. however, because it can have that happen, better to replace it prior to breakage.

 

At 250k and 30 years I'd expect both the chain and headgasket having been done at least once. But if not, I can't imagine a better promo for factory parts.

 

.011 and .007 are the cold lash clearances, while the factory recommendations are for a hot engine, so they are not interchangeable.

reducing valve lash = less time for the closed valve to sink heat into the head, so it's not advantageous for engine life.

more valve lash is effectively milding the cam profile, so you could argue weaker performance, but i think that it's going to be insignificant in real-world performance.

what i found with noise is that tightening the front two valve cover nuts can make a big difference, but the rear nuts not so much.

 

First of all. Don't fix anything that's not broke.

Just like @Jimkola said. The guides are mostly likely plastic. If one of them are broken/missing, then yes it's time for a timing gear set. If a guide is broken, most likely you will have chain slap on cold starts especially in the morning after it has sit over night. Chain slap will eventually wear a groove into the timing cover, and then coolant will get into the engine oil.

About the valve lash. I tried doing it hot, and it was just a PITA, so I set mine 11/7 cold. Bought a new bolt on head, new timing chain set, new water pump, Toyota head gasket, and new oil pump about six years ago, and it's been running fine to this day. On the head, I just used the old rocker assembly, and did not change a thing on the rocker assembly. Mine ticks lots, but runs great. Pretty sure if I would have reconditioned the rocker assembly, engine would be a good bit quieter. Anyway, good luck with the truck!

 

When you have that valve cover off, I'd try to snake your borescope down along the cam chain to inspect the guides. Borescopes are so cheap these days, there's no reason not to own one.

I've not tried this (didn't own one last time I had the valve cover off), but maybe others can comment on how easy it is to see the guides using a borescope when the valve cover is off.

My primary engine noise is piston slap when it's cold. Just at a certain RPM range, and only when the engine is just barely loaded. Like cruising at 25MPH in 3rd gear on a flat road. Goes away after just a few minutes of operation after overnight lows around 50degF. Note that I'm assuming this is piston slap rather than chain slap, but maybe others feel this is incorrect.

 

Piston slap fits your decription. It was a common complaint by some bitd.