I just bought a decent 1984 toyota pickup 22re with 376k miles on. When I bought it, I could hear that there was a slight whur in the engine which I deduced to being the timing chain rubbing up on the housing of the timing chain cover. I didn't strike it as a massive issue if I fixed it as soon as possible, but I didn't have the chance. The chain broke on me a couple days later in a Walmart parking lot when I tried to start it, luckily it started and immediately broke and died. When I stripped everything off to uncover the timing chain it was definitely broken but just laying in the bottom loosely wrapped around the bottom sprocket, not bound up, didn't cause any extra damage on anything that I saw, replaced the timing chain, tensioner, guides, sprockets, oil pump, water pump, oil pump screen in oil pan, spark plugs, belts. Anyways, once I struggle ˟˟˟˟ed with replacing the timing chain and making sure that the timing was on point with TDC, I could get the truck to start after adjusting the distributor cap, but it was running really rough and rocking, I remembered while checking TDC and checking the rocker arms that the 4th cylinder exhaust and ignition arms had way too much play in them regardless of which cycle it was on. So I did a leak down test as well as a compression test. I checked my first cylinder just to confirm that it was reading, and it read around 140 psi which from what I've read is about 15-20 psi less than stock, which also made sense from what I've read about high mileage motors over time wearing it down to a lower compression rate. My 4th cylinder didn't read anything at all, mean literally didn't pickup on my compression test. So this is my work vehicle and it has now been down for 2 weeks. My boss just says to do a valve job on, but multiple mechanics have told me that just replacing a valve or even all 4 of them for that matter will only make the piston rings go and a bunch of other things in the block that are worn down. So I have mechanics that are trying to tell me to but a new engine and put it in, and my boss ( who is paying for it as a loan) who is saying ˟˟˟˟ them, just do the valves. The engine rebuild project would cost around $3,000- $3,500 taking it to a shop,, whereas the valve job would only cost about $1,000 if I did it myself. But I don't want to put that much more money into it, I bought it for $4,000. If I rebuilt the engine there is no way I would ever get my money back on the vehicle if I tried to sell it in the future. Please help me out I am on a time crunch and can't really trust these mechanics or my boss at the moment, been tugged around too much already.

 

It could well be the #4 cylinder's valves, no doubt.
But, with the valves loosey-goosey, it seems to me that the compression should read something. It's not, though, which could well be the piston rings. I mean really, if the valves are at the #4 TDC, and they're sloppy loose as you say, it seems to me like the valves would be closed down tight, and hold compression in. At least SOME compression...
Maybe I'm wrong. Maybe it means the valves are destroyed, not closing at all, thus no compression. If they are, they would need replacement. Which, in turn, means pulling the head. New head gasket, and so forth. If the valve's ports are chamfered out badly enough, I believe you'd need a new head.

The mechs are right, too. It gets a head job, which is essentially what it would take, how long until the piston rings fail, or the rod bearings, thrust washers, whatever. And they would, probably sooner rather than later. A new engine, or a rebuilt one, anyway, would solve all those problems. More expensive, yes, but personally, I think, worth the cost. Just my opinion, though. Whatever it's worth.
I'm not a "bottom end" mechanic. At ALL. I've replaced the head in the 87 4Runner (twice. Got a "new" one that came pre-cracked for me. So considerate), but that's as far as I've ever gone. I'm an electronics tech by trade, nothing more than a shade tree mech. I'm probably completely wrong, and a new head will solve all your problems. I don't know.

Not much of an answer, I'm afraid, but it's the best I can offer.
Pat☺

 

Well, the truck has 376k miles on it? As far as you know, the engine has almost 400k miles on it? There is no way I would spend $1000 on a valve job and leave a bottom end alone with that many miles. This is a deep well you are tapping....I mean if I were going to touch that engine with that many miles, I would yank it out of there...then you start talking new clutch, machine flywheel, cleaning injectors, intake, fuel filter....starts adding up quick, but sometimes you have to just bite the bullet.

 

If you do pull the head, i bet what you will find is a burnt or bent exhaust valve on #4. That would certainly account for no compression. If it were the rings on 4, you would see terrible oil consumption. Many millions of engines have been the recipients of what used to commonly be called a “valve job”, typically seen on this forum after an overheating episode and loss of head gasket. The valve job itself won’t be responsible for killing of rings, they were only partially efficient with that mileage anyway. I can see if you were planning to add a turbo or supercharger which would increase cylinder pressure beyond normal specs. Then of course you would want a fresh bottom end in best condition possible to get the most out of your modifications.
But with this kind of mileage, typically 2 lives for a 22re, I can see why others and mechanics are telling you not to thro money at it.
At this point your best option may be a good running used engine. That’s how i would go..

 

If it threw the chain then it's very likely the valves are bent. Looks like you bent the valves on #4. Those valves have excess lash because the valve is bent and cannot close all the way, leaving an abnormally large valve lash. You also will get zero or near-zero compression with a bent valve.

Obviously, the best answer to any issue is an engine rebuild. But unless you really love the truck and have lots of money it's probably not what you want to do now.

If you just need the truck to work like it did before, you could pull the head, slap in two new (or even used) valves and lap them in, put on a new head gasket and be done for $250. I've never bought into the theory that working the head on an old block will immediately result in the bottom end giving up.

 

I replaced the head in my 87 4Runner after a "friend" threw the water pump belt, and overheated it repeatedly getting it to my house. Yeah, some friend.
I had to do it twice, as the first "new" head was cracked when I bought it. They replaced it for free, but I still had to do the work myself. New head, with new valves included, new gaskets all over the place, including a head gasket, and it's worked great ever since.
Not that many miles on the new head, but a lot of time. I think I have put about 20K miles on it so far, but over 20 years time. Ever since I was forcibly retired for medical reasons, I don't have the hour's drive to work any longer, and since the kids are grown and gone, I don't have to drive them around any longer. I don't get many miles on, just a long time, now.
My mechanic replaced the timing chain and CV shafts for me, and the water pump that blew just as he was testing it out, a few years ago. Small stuff, just needed to be done after 30+ years, even with only 177,000 miles on it. Basic maintenance. The engine's bottom end seems to be holding up wonderfully.

Have fun!
Pat☺