valve lash Q & pics

[porcupine73]

Hello, taking advantage of the long weekend to adjust the valve lash on my 2000 Subaru Outback 2.5L 4 cyl (non-turbo). I few questions came up while doing the job (got the right-hand cylinders done today). First, the engine has 105k miles on it; don't know if the valve lash was checked before. The specs are [engine cold]: intake; 0.20 +/- 0.02 mm exhaust 0.25 +/- 0.02 mm. (1) Before I adjusted, intake was about .10mm and exhaust was about .15mm. Would you say this is about normal recession for 105k miles? (2) How critical is the valve clearance? I mean if I'm a little over the tolerance is that a big issue? I tried to err on the side of too much clearance, esp. on the exhaust valves because my understanding is that if the valve doesn't close completely it will get scorched. (3) I got some very fine dirt particles on the doohickeys inside the valve cover when taking it off; is that bad? I tried to flush it off with fresh engine oil which helped a little but didn't get it all. (4) My right-hand bank cylinder bank pics with the valve cover off are below. Do they look OK? I didn't see any sludge in there; I cleaned the valve cover with some Scotch Brite and brake cleaner. I thought it was kind of funny the OEM manual refers to the valve cover as the 'rocker door'. I learned a couple lessons so far: first, make sure you're actually measuring in the units specified. At first, I was inadvertetly measuring in inches my feeler gauges instead of millimeters. Thanks! Louis

 

[JavaMan]

Very clean. What type of oil are you using?

 

[porcupine73]

JavaMan, ran Amsoil HDD 5W-30 for a couple thousand miles, then switched to my own mix of mostly Amsoil S2K 20W50 with one bottle Amsoil S2K 0W30 (plus some Schaeffer's #132 Moly E.P. and some Specialty Formulations wear stuff, forget the exact name). Owned the vehicle since about 98k, so I've put on a about 7k miles since I bought it last year; don't know previous service history. Ran the Amsoil engine flush right after I got it.

 

[mechtech]

I find that engines with high mileage and never having a valve clearance adjustment get looser with those types of adjusters. Nothing to worry about , though. I bet you picked up a little more noise and a little more lower end torque. Nice and clean, BTW!

 

[Clyde65]

porcupine73

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How critical is the valve clearance?

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Very critical. Why can't you get them set perfect? Remember, the valve must be open when making the adjustment.

 

[porcupine73]

Thanks for the info MechTech. I haven't driven it yet since I have to do the other bank today plus I plan to replace the timing belt while I'm in there. Clyde65, thanks for the info. The problem I was having was I would set the crank at TDC for the cylinder then check/adjust the intake&exhaust. Then the manual says to rotate the crank two full revolutions and recheck. When I would recheck, it seemed the clearance had 'grown' by mabye .01mm. I think what I was doing wrong (maybe?) was the first few times I missed TDC by a few degrees, so I nudged the crank backwards. That's when it seems the clearance was too wide. If I rechecked by turning only in the correct direction and not nudging back then the clearances seemed to stay consistent with where I set them.

 

[ex_MGB]

Do a google on "cleaning engine with Scotchbrite"...

 

[Bill in Utah]

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Originally posted by Clyde65: porcupine73

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How critical is the valve clearance?

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Very critical. Why can't you get them set perfect? Remember, the valve must be open when making the adjustment.

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The valves should be closed and the cyl at TDC for adjustment... Thats the way I've adjusted valves for over 30 years... How do you adjust when the valve is open? (and rocker arm is pressing on the valve stem) Am I confused here? Bill

 

[Drew99GT]

It looks like they measured all tight. Was the engine absolutely stone cold ambient when you checked them?

 

[porcupine73]

Well, this is my first time doing valve clearances. The engine was at ambient when I worked on the valve clearances; it's about 75 deg. F in the garage; engine hasn't been run in over 48 hours. What is the consequence of the clearances being a little to big? I read the exhaust valves will scorch if there is no clearance (i.e. the valves don't fully close and have no chance to dissipate heat into the valve seats). If the clearance is a little too much, what happens? Maybe more clatter and less power? The valves were closed when I checked the clearance; I could wiggle the rocker a little bit (the clearance). I checked the right hand-bank today. On the RH bank, the intake valves were fine on both cylinders (a tad snug, but I could still fit the .20mm feeler gauge in there), so I left those alone. The exhaust valves were a little tight on the RH bank so I opened them slightly to .25mm per specs. I think what might have been happening is I was a little past TDC on some of the exhaust valve measurements making it seem like they were tight. Anyway, I triple checked them all before putting the valve covers back on and was happy with the readings. Now it's on to replacing the timing belt. Got the crank pulley off today, man the bolt in it onto the crankshaft was tight, but my huge harbor freight chain wrench and a pipe on the end of the breaker bar let me free it up. Thanks for all the help guys! I guess the test will be what happens when I try to start the engine.

 

[reyjay1]

Last time I remember adjusting valves it was as a kid, and Dad always did it with the engine running. seemed pretty easy that way and seemed to work. Does nobody do it that way anymore? Maybe would not work so well on a slant or V motor?

 

[porcupine73]

Interesting method reyjay1. I don't think I could do it that way because as far as I can tell oil circulates somehow under the valve covers and if I ran the engine with the valve covers off I think a whole lot 'o oil would come spilling out plus the rockers (which have the adjust screws) would be bopping up and down. The Subaru engines are a horizontal cylinder design and the valve covers are horiztonal. My other Subaru (1996) has hydraulic lash adjusters and I'm not sure yet if checking the lash is needed on it?

 

[johnd]

Between Air Cooled VW engines and motor cycles I have probably adjusted enough valve lash to be able to do it in my sleep. Yes, if they are too tight the valve won't close and can burn. If they are too loose you get noise and lack of power. Usually they get looser with time but not always. The best policy is to try to get it as close as you can. "Perfect" is when you can draw the feeler gauge through the gap and feel the same amount of resistance on every one as you do it.

 

[Drew99GT]

Yea, if your other Sub has hydraulic lash adjusters then they don't need to be checked and adjusted regularly. If cylinder was a couple degrees past TDC that wouldn't make a difference because the camshaft would till be on it's base circle; you'd have to go to bottom dead center on the power stroke for the exhaust lobe to start pushing the valve. It sounds like you got it good. Just be happy you have the little adjusters and not shims to deal with! The Toyota style valvetrains can be a pain to do the first time cause you have to use a special tool that keeps the valve open so you can use a magnet to cling onto the shim and pull it out.

 

[vizvo]

Hey porcupine73, you are correct. It is better to have a tad too much clearance than too little. Too little clearance and the valves won't seal, and the exhaust valve will burn. Over 40 years ago, I was taught how to adjust valves by a really top notch automotive machinist. Allow me to share his really good technique with you. First, he taught me that the valve you are adjusting should always be closed. It makes obvious sense when you think about it. Second, he said the only reason for the specs saying to have the piston at TDC when you are adjusting that set of valves is to ensure that the valves are closed. Third, he said the same result could be had a whole lot quicker by using a different technique. The technique he taught me was to bump the engine over until one of the valves at the cylinder of interest is completely open. Then adjust the other valve on that cylinder (which would obviously be closed). He said the reason for this method is that it is a lot faster than trying to determine exact TDC. And that it is much easier to determine when a valve is open than when it's fully closed. Being a machinist, he pointed out that when a valve is fully open, that by design, the other valve must be fully closed. It is this closed valve you want to adjust. So anytime one valve is fully open, you are free to adjust the other valve in that cylinder without worry. I've followed this advice for four decades and have never had a problem. [ July 04, 2006, 11:38 AM: Message edited by: vizvo ]

 

[Drew99GT]

Most shop manuals will give you the exact procedure so that you do one set of valves when the number one cylinder is at TDC compression then you turn the engine over 360 degrees so that the remaining valves can be checked.

 

[JHZR2]

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Originally posted by porcupine73: Then the manual says to rotate the crank two full revolutions and recheck. When I would recheck, it seemed the clearance had 'grown' by mabye .01mm. I think what I was doing wrong (maybe?) was the first few times I missed TDC by a few degrees, so I nudged the crank backwards.

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Ive noticedthe same phenomenon in my 83 MB turbodiesel... they seem to 'grow'. Too lose is etter than too tight (at least for my engine)... they tighten over time. Do not ever crank the engine backwards, even just a tiny bit - this can do bad things for timing. If you miss, you need to go around again. JMH

 

[Clyde65]

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Originally posted by Bill in Utah: The valves should be closed and the cyl at TDC for adjustment... Thats the way I've adjusted valves for over 30 years... How do you adjust when the valve is open? (and rocker arm is pressing on the valve stem) Am I confused here?

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I had a 50/50 chance of being right when I made that statement.

 

[mechtech]

I use TDC for each cyl., or point the lobe away from the contact point. If you use the method where you adjust the opposite valve when it's counterpart is open, you may have trouble with a tight intake. You MAY be sneaking up on a clearance ramp, with some cam grinds. The valves overlap and are both open at some point - some more, some less. It should be OK to us this method for the exhaust valve clearance, though.