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Old 08-11-2014, 12:28 AM   #1
kj7687 OP
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Question Valve adjustment question! Please advise!

Firstly, this is a question pertaining primarily (though not entirely) to my recently-purchased 99 Toyota 4Runner, so I hope I'm not breaking any forum rules lol... If I am, please don't ban my account. I'll take this down or whatever...thanks :)

I'm in the middle of a valve adjustment on the 2.7L inline four cylidner 3rzfe engine in my 4Runner. I have found that most of the intake valves are barely tighter than the tightest side of the clearance specifications (I'm sure they'll be fine after adjustment...), and all of the exhausts valves are quite a bit tighter than the minimum specification (they are fairly close to each other and average about .0065 inches, while the specification is .010 to .014 inches).

My question is this: I understand that tight valves can get burned over time because they stay open longer or even never fully seat (valve float at high rpm?). I hope someone with a lot of knowledge in this subject can tell me a little more about this. Specifically, I'm wondering how tight is generally so tight as to cause this phenomenon of burning valves. Is it something to worry about at 50 to 80 percent of minimum clearance specification, or really only a serious issue when clearances approach or reach zero? I understand it may be different depending many factors such as timing, engine temps, engine rpm, etc... Also how long would it likely be before serious damage is caused? I realize there are a ton of factors to consider here, so I'm really l looking for general information regarding this cause of valve burn, and also specific information as to whether or not my engine, with the above clearances on the exhaust valves, is in danger of serious damage? Of course I have no idea how long the valves have been tight, or how quickly they've tightened up, as I just bought this vehicle...

My 4Runner exhaust valve clearances are roughly 65% of the minimum specification; I owned a Ninja 500 for a few years that had extremely tight valves when I adjusted them at 5,000 miles (they were about 30% of the minimum specification!). After the adjustment, the Ninja ran awesome (with the expected improvement in engine warm-up, idling, and low RPM performance seen after loosening up the exhaust valves), and the valves didn't move much over the next 13,000 miles. So I assumed that no real damage had been caused in that case. Then again, the Ninja couldn't possibly have been running those tight clearances for longer than those 5 thousand miles! Again, I have no idea how long the valves have been tight on the 4Runner, but I'm hoping that I can get them adjusted to spec and all will be well. I REALLY need this vehicle to be reliable for AT LEAST 5 years/30,000 miles...and I'm on a college budget and working/studying 70 hours a week, so I sure hope I won't have to poor a sh** ton of time and money into expensive head work...


I'm really hoping someone way smarter than me can help me out with this one. Thanks in advance!
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kj7687 screwed with this post 08-11-2014 at 12:41 AM
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Old 08-11-2014, 02:20 AM   #2
Morizzi
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Well in the words of the Hitch Hiker's Guide to the Galaxy, "Don't Panic!"

Smarter? Not sure I qualify. Don't know the vehicle or that particular engine but think about it, why would there be less clearance? Sorry it really doesn't relate but I like throwing in a every now and then.

Tappet or cam wear would mean bigger clearances as would rocker wear . The primary suspects here are valve stretch or seat regression

The main issue as I see it is you don't have a base set of values to compare to.

What I'd do: Set the valves as they should be and record any other issues. Drive the thing then in a reasonable amount of time re-check the valves. If they haven't change then spend you money on this: . If they have then I'm sure you can work it out.

I have a friend into vintage motorcycles. he has a 1928 Norton that needs external valve lube. He swears that the valves stretch with normal oil but if he adds moly disulphide to the oil they don't. Take from that what you wish.

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Old 08-11-2014, 04:56 AM   #3
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It becomes a problem when the valves get to 0 clearance while running. Which would be more than 0 clearance while cold, but if I had to guess I would call it 25-30% of the minimum clearance spec would start to be an issue.

You must have a crap load of miles on the Yota motor to actually need to adjust any of the valves. Most of their engines go to the junker without ever needing a valve adjustment.
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Old 08-11-2014, 08:25 AM   #4
kj7687 OP
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I try not to worry so much but can't help it... I'm already shelling out quite a bit of time and cash for a new gasket and all those shims :( Unless I can "trade" my shims for the ones I need (never done adjusted shim valves before)?

Yamarocket: The current tight clearances could have been this way since only a few thousand miles after break in (high initial wear), or it could have happened gradually over the life of the vehicle, eventually reaching the current specs, or suddenly at high miles due to overheating or abuse or something... Unfortunately I guess there's really no way of knowing that at this point. The motor has 155k miles on it. I'm not sure I'd call that a crap ton lol but it isn't exactly low miles either. I know what you mean about not having anything to compare the current specs to. I wish I did. So anyway, you're saying that the valves won't start to burn until you get zero clearance when hot? And mine (at 65% of min. spec.) probably won't get that tight when hot, so I should be okay as long as they get adjusted now? Any idea how fast you'd have serious issues after starting a zero clearance when hot scenario? I'd guess pretty fast, like maybe 5k or 10k miles?
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kj7687 screwed with this post 08-11-2014 at 08:32 AM
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Old 08-11-2014, 09:05 AM   #5
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As people who can cook may say: "The proof is in the pudding". Or, to put this another way, if it still runs OK - then it's ok.

I would adjust the valves to the middle range of their clearance then check them at the next oil change. If the valve aren't receding any or (~ 0.001") then check them again on the same interval. If the clearances stop getting smaller, checking at every other oil change is what I would do. But, there is some evidence of valve seat recession so don't ignore the valve clearances for the next 30,000 miles.

Good luck!
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Old 08-11-2014, 10:16 AM   #6
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a valve that is "in spec" is.... in spec.... it's fine... you can even leave it alone. an exhaust that it too tight may actually be open during the combustion process & that can burn a valve. an intake that stays open would result in backfiring into the manifold. in the days of carburated engines it could make quite a bit of noise

set the ones that are out & drive on

and hydraulic lifter engines run at zero clearance all the time.... hence the phrase "zero lash lifter"
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Old 08-11-2014, 10:52 AM   #7
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If you're already in there, adjust any that are even close to out of spec.
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Old 08-11-2014, 03:14 PM   #8
disston
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I don't know Toyota $Runners. But the problem with lots of engines today is valve seat recession. Newer materials in the valve seats address this issue but you don't say what year this car is. I think when you find somebody with the info you need it will be year specific problem. The fix is most likely to be adjust them and keep an eye on them.

It might be a good idea to have a spare cylinder head.
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Old 08-11-2014, 03:51 PM   #9
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Quote:
Originally Posted by kj7687 View Post
I try not to worry so much but can't help it... I'm already shelling out quite a bit of time and cash for a new gasket and all those shims :( Unless I can "trade" my shims for the ones I need (never done adjusted shim valves before)?

Yamarocket: The current tight clearances could have been this way since only a few thousand miles after break in (high initial wear), or it could have happened gradually over the life of the vehicle, eventually reaching the current specs, or suddenly at high miles due to overheating or abuse or something... Unfortunately I guess there's really no way of knowing that at this point. The motor has 155k miles on it. I'm not sure I'd call that a crap ton lol but it isn't exactly low miles either. I know what you mean about not having anything to compare the current specs to. I wish I did. So anyway, you're saying that the valves won't start to burn until you get zero clearance when hot? And mine (at 65% of min. spec.) probably won't get that tight when hot, so I should be okay as long as they get adjusted now? Any idea how fast you'd have serious issues after starting a zero clearance when hot scenario? I'd guess pretty fast, like maybe 5k or 10k miles?
So anyway, you're saying that the valves won't start to burn until you get zero clearance when hot? Correct. A closed valve doesn't burn. A valve with > 0 clearance is fully closed. That's how hydraulic valve lifters work, they maintain the valve clearance as close as possible to 0 clearance. My guess it gradual wear, anything that would cause accelerated wear would have caused catastrophic failure by now.

And mine (at 65% of min. spec.) probably won't get that tight when hot, so I should be okay as long as they get adjusted now? Again, correct. There is a safety margin built in for extreme conditions and wear.

Any idea how fast you'd have serious issues after starting a zero clearance when hot scenario? I'd guess pretty fast, like maybe 5 or 10 miles? FIXED... maybe a bit of an exaggeration, but my number is closer than yours most likely.

Quote:
Originally Posted by disston View Post
I don't know Toyota $Runners. But the problem with lots of engines today is valve seat recession. Newer materials in the valve seats address this issue but you don't say what year this car is. I think when you find somebody with the info you need it will be year specific problem. The fix is most likely to be adjust them and keep an eye on them.

It might be a good idea to have a spare cylinder head.
The 2.7L Yota engine appeared in 1995. It has hardened valve seats as leaded fuel had been gone for 20 years by then.

Quote:
Originally Posted by Stan_R80/7 View Post
As people who can cook may say: "The proof is in the pudding". Or, to put this another way, if it still runs OK - then it's ok.

I would adjust the valves to the middle range of their clearance then check them at the next oil change. If the valve aren't receding any or (~ 0.001") then check them again on the same interval. If the clearances stop getting smaller, checking at every other oil change is what I would do. But, there is some evidence of valve seat recession so don't ignore the valve clearances for the next 30,000 miles.

Good luck!


The valve adjustment interval is 60,000 miles. Why on earth would you recheck it 3-5k miles after an adjustment? It's not a formula 1 engine, its a light truck engine designed to go many thousands of miles without having it's valves inspected or serviced.

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Old 08-11-2014, 06:43 PM   #10
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Quote:
Originally Posted by Yamarocket630 View Post

The 2.7L Yota engine appeared in 1995. It has hardened valve seats as leaded fuel had been gone for 20 years by then.





The valve adjustment interval is 60,000 miles. Why on earth would you recheck it 3-5k miles after an adjustment? It's not a formula 1 engine, its a light truck engine designed to go many thousands of miles without having it's valves inspected or serviced.

Because... that's how I roll. Don't like it? Fine with me. Don't do that.

One reason for the valve clearance is because the valve will expand when hot. The valve length increases with heat which reduces the valve clearance even more. Without adequate valve clearance, the valve does not have time on the seat to transfer heat out of the valve.

There is obviously something not right when the valve clearance specification is closing 3.5 mils from the minimum spec. I think it is valve seat recession. But, if anyone has a better theory - let's hear it.
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Old 08-11-2014, 11:34 PM   #11
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Thanks!

Thanks very much for the detailed answers! I'll get them all in spec and get all the other maintenance done, and hopefully this damn thing will get me through college! If it doesn't, I will simply be car-less between the time it craps out on me and the time I graduate and get a real job...because I won't be able to afford another POS, and there's no way in hell I'll ever sell my KLX! I hate used vehicles.
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Old 08-12-2014, 02:52 AM   #12
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You own a motorcycle and live in California, if your Toyota eats itself there are far worse positions you could find yourself in. Adjust the valves, check in a few months, and don't worry so much.
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Old 08-12-2014, 04:50 AM   #13
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It made it 155k miles without ever likely having the valves adjusted. Get them in spec or a close as possible with the shims the dealer MIGHT have available and forget about it. It will go to the scrap yard or the next owner with them still in spec.
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Old 08-16-2014, 02:37 AM   #14
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With that low of miles, I would bet the valves had never been checked. Adjust them and check again in 30-60k.

Even badly burned valves will seal again with enough time. One on my Toyota got very tight and I got zero compression on that hole. I could put my thumb over the spark plug hole while running and got nothing.
It was way past zero. I re shimmed it just past the loose side of the spect, figuring it would seat in some. Some compression came back, and more and more came back each time I checked it on each spark plug change. I never got to normal compression, about 20psi low, but that is still darn good for the abuse it took.
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Old 08-17-2014, 12:37 AM   #15
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remember that the head expands too, and aluminum has a higher coefficient of expansion than any steel/nickle, etc valve alloy

is there seat recession on your engine? dunno, but once they are worn in and have been set to spec they should be good for at least the minimum stated by the manufacture, and probably double that. it's the first check that really counts
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