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Valve clearances

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David G

Well-known Member
If valve clearances are getting tighter due to recession, would you expect issues at idle or higher RPM?
 
(quoted from post at 17:42:16 02/09/15) If valve clearances are getting tighter due to recession, would you expect issues at idle or higher RPM?
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To a point---Both. I would suspect you would have more of a problem at high rpm especially with a very high performance engine where "valve float" could be an issue (less clearance = less time to close)
 
Yes

When you factor in the beef prices, what used to be known as tenderloin is now called elevenderloin.
 
If its a low speed tractor engine with solid lifters probably can't tell the affect difference of high and low. But if you could measure I would guess idle and off idle in the above engine if all valves are still closing.
 
Well when my sisters 1999 Honda CRV lost valve clearance on one exhaust valve it was turning on a cylinder misfire code ,then it would miss at idle and not noticeable at higher speeds. This went on too long and burnt the valve !
Even Honda dealers deny these had this issue but google is full of people that had the same problem on this year.
I still get a kick out of the Honda owners manuals that say no adjustments needed unless noisy. Well for this problem noise is your friend. When the noise is gone so is your clearance !
 
(quoted from post at 17:42:16 02/09/15) If valve clearances are getting tighter due to recession, would you expect issues at idle or higher RPM?
Click to expand...

At idle. If the lash is tighter then that means the valves are opening sooner and closing later. It's kind of like running a bigger cam. At higher speeds there is less time for anykind of bleed off so it would be less noticable. Back when I built some motors for drags cars, if you wanted less wheel spin on take off you could tighten the valve lash up some, if you wanted more bottom end power you could open the lash up. Of course this is on solid lifter engines.
 
This is on my daughters 1994 corolla, it does not have a miss, but a vibration at idle that I am trying to track down.
 
I would guess you would see it more at idle.
Fixed an engine for a neighbor a few years ago.
When cold one valve was too tight would not quite seal and the rpm would hunt around and stall untill it warmed up.
Once warm things expanded a little increasing the clearance and letting the valve fully close and it would idle fine
Quick valve set and it ran great
High end will probably be loosing some power but harder to detect.
 
David; Did you google the 1994 Toyota corolla vibration at idle .
A lot of others had that same issue. Happy reading !
 
As the valves begin to "beat" in the seats, valve clearance could decrease. But, if the engine has hydraulic lifters/followers/lash adjusters, there is no adjustment. The lash is inherent in the design.
If you are looking for a vibration or roughness as noted below, I believe that most compact car engines have balance shafts in them. The mechanism that drives the balancer could have gotten loose enough to cause a noticeable changes of idle quality.
 
I have checked the motor mounts, none are loose. It does not miss, just a little rough at low RPM's that make it vibrate inside the car. I am going to check out the timing and the valve clearances next
 
My experience has been hard starting and erratic idle speed. It may change somewhat depending on the engine. The overhead cam water cooled engine was more hard starting, the air cooled push rod engine was more erratic idle.
 
Check the motor mounts closely, they may not be loose or broken, but sagged enough to loose their resilience or allow a metal to metal contact somewhere. Also look over the exhaust mounts, listen to the converter to hear internal rattling. EGR sealing off completely?
 
The motor is tight in the mounts laterally, I will check out the top mount. There is a lot of bad press on that one.
 
(quoted from post at 09:13:56 02/10/15) The motor is tight in the mounts laterally, I will check out the top mount. There is a lot of bad press on that one.
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I have owned my share of them more than likely engine mount issues.. Engine mounts (insulators) absorb vibration does it do it in forward and reverse... Honda's had a air adjustment on the throttle body I am not sure on a yota... Honda's suffer from the same engine mount issue sometimes you can tweak the air and smooth them out but never eliminate the vibration unless you go after ALL the engine mounts....

They were great cars and the vibration is a common issue... I work on one it will buzz the whole care at idle in gear off idle the buzz is gone he lives with it because he does not want to shell out the cash for the mounts they are expensive...
 
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