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22Re valve adjustment Cold or Hot?

When adjusting valves on a 1986 22RE Toyota engine, the manual says to adjust intake to .008 and exhaust to .011 when the engine is "hot". I was doing some research and it seems to be a somewhat common practice to adjust valves on these engines to .007 intake and .011 exhaust when the engine is cold. The explanation being that the clearances will open up some when the engine warms up or gets to "hot". I always thought the clearances would get tighter as the engine warmed up but my "knowledge" is based on traditional pushrod engines and this is an overhead cam engine.

If adjusted cold, will the clearances get smaller or larger when the engine is hot?

And is it ok to adjust the valves cold?

And how hot is correct amount of hot if I adjust them according to the manual?

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Comments

  • edited January 2011
    Sorry, I should have said the manual states .008 intake and .012 exhaust and adjust when hot.
  • edited January 2011
    Hot is normal operating temp.
  • edited January 2011
    One other thing I notice on this engine when adjusting the valves, the base circle on the cam seems to vary by a couple of thousands. This is an aftermarket (stock replacement)cam. Engine rebuilt 5,000 miles ago. If valves are adjusted by the Factory Service Manual, you set engine to TDC for cylinder one and then adjust 4 valves, then rotate crank 360 degrees (now set to TDC for cylinder 4) and then adjust remaining 4 valves. So, cylinders 1 and 4 are adjusted when at TDC but 2 and 3 are not. With the varying base circle on the cam it seems like the adjustment from cyliner to cylinder will not be the same. Would it be best to adjust when each cylinder at it's TDC or adjust each valve when the lobe is opposite the rocker?
  • edited January 2011
    It seems logical that an aluminum head, if that is what you have, has a faster coefficient of expansion than steel valves so lash will decrease as the head expands faster than the steel on heating. The exhaust valve will run hotter than the intake valve so you have more initial lash specified. That will be needed for times when the engine is run at full power.

    If you can't idle the engine while checking clearance then it would be reasonable to heat the engine, shut it off, pull the valve cover and check clearances soon. The difference in the cold and hot lash numbers that you provide indicate that the degree of hotness is not critical.

    With no direction from the book, I would check the lash with the cam lobe opposite the follower.

    Aren't hydraulic valve lifters wonderful?
  • edited January 2011
    "the base circle on the cam seems to vary by a couple of thousands. This is an aftermarket (stock replacement)cam."

    You've almost answered your own question.
    If the top of the lobe is reduced then the base circle must be reduced too, in order to get the same relative lobe height.
    Since the donor cam wasn't worn equally on each lobe and the grinder probably removes a minimum amount of material the base heights will vary lobe to lobe.

    "So, cylinders 1 and 4 are adjusted when at TDC but 2 and 3 are not. With the varying base circle on the cam it seems like the adjustment from cyliner to cylinder will not be the same."

    With 1 and 4 at TDC suppose 2 is at the end of the intake stroke and 3 is at the beginning of the exhaust stroke.
    In that case #2 exhaust lobe is on the base circle and should be the same lash as half a crank turn later.
    #2 intake valve is open.

    Also, #3 intake lobe is on the base circle and should be the same lash as half a crank turn earlier.
    #3 exhaust valve is open.

    Turn the crank 360 degrees and the roles of 2 and 3 are reversed.
    The actual base circle height doesn't come into play.
  • edited January 2011
    Aren't hydraulic valve lifters wonderful?

    Not really.
    They can fail, get clogged, cause noise, or decrease valve lift, which then reduces vehicle performance.

    Once a direct system is adjusted, it simply works.

    BC.
  • edited January 2011
    "You've almost answered your own question.
    If the top of the lobe is reduced then the base circle must be reduced too, in order to get the same relative lobe height.
    Since the donor cam wasn't worn equally on each lobe and the grinder probably removes a minimum amount of material the base heights will vary lobe to lobe."


    I don't think I've explained what I'm seeing very well. The two thousands variance I was seeing is not a variance from one lobe's base circle to another lobe's base circle but rather the variance I'm seeing is on the same lobe. When the valve is fully closed, the clearance on some of valves changes as you rotate the cam. I realize that the clearance is going to change right after the valve closes and right before the valve opens but once the base circle is under the rocker arm I would think the clearance should be consistent until cam lobe comes back around to start opening the valve again.

    Here's another way to look at it, if I adjust the #4 cylinder intake and exhaust valves when this cylinder is at TDC, then check the clearance on each of these valves when that valves cam lobe is 180 degrees from the rocker arm, the clearance is different, by up to about .002" and only on SOME of the valves.

    When the lobe is 180 degrees from the rocker, I would think the cam under the rocker arm is at base circle.

    Since (by the book) not all valves are adjusted when their cylinder is at TDC, only 1 and 4 are, it seems like the maximum valve clearance for each intake, or each exhaust valve, will not be consistent from cylinder to cylinder.

    It seesm like I should not follow the book and adjust each cylinder when that cylinder is at TDC, or perhaps adjust each valve when the associated cam lobe is 180 degrees from the rocker.
  • edited January 2011
    "the variance I'm seeing is on the same lobe"

    Well, that's a whole different ball game!

    That's a lousy grinding job. Maybe the base circles are off-center.

    I would set the lash at the tightest part of each base circle, so the lash is always at spec or a little looser.
    Hopefully the valvetrain will run quiet enough under this condition.
  • edited January 2011
    "It seems logical that an aluminum head, if that is what you have, has a faster coefficient of expansion than steel valves so lash will decrease as the head expands faster than the steel on heating. The exhaust valve will run hotter than the intake valve so you have more initial lash specified. That will be needed for times when the engine is run at full power."

    Yes, this is an aluminum head and steel valves. But this is an overhead cam. I think you need to consider the geometry and relationship of the cam, rocker, and valve. I am not qualified to fogure all that out to know if the end result will be less, more, or basically the same valve clearance when hot or cold. Since the manual stated to adjust hot, I assume there may be some change with temperature changes.

    "If you can't idle the engine while checking clearance then it would be reasonable to heat the engine, shut it off, pull the valve cover and check clearances soon. The difference in the cold and hot lash numbers that you provide indicate that the degree of hotness is not critical."

    On this engine, it's not possible to check clearance when it's running.

    I don't think I can make an assessment of how much the lash will change from a cold to hot engine. I was hoping someone might have actual experience on a 22RE to know since I saw a number of online references to adjust to .007 and .011 when cold, and the book says to adjust to .008 and .012 when hot. That just seemed backwards to me.
  • edited January 2011
    "I would set the lash at the tightest part of each base circle, so the lash is always at spec or a little looser.
    Hopefully the valvetrain will run quiet enough under this condition."

    Thanks, this is what I did. I thought having the valves a bit loose might be better than tight. Yes, I can hear the valve train when the engine is running but its not unususally loud or uncommon on these 22RE engines.
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