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Valve clearance with timing belt off, valve shim questions


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4 replies to this topic

#1 bearbalu

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Posted 19 December 2004 - 02:24 PM

1) I am doing head gasket job...I measured the clearances with timing belt "on"as described in Haynes/Subaru Service manuals - ( measuring with the arrow on right intake cam sprocket at specific positions - 2:30 pm, 4:30pm, 8:00pm, 11:30pm) ). Specific valves are under no tension (zero lift) at these specific positions.

A few questions:

2) When putting in new shims, to double check the clearance, can I just do it with timing belt OFF with values at "zero lift". If so, wondering if the procedure procedure described in 1) above be modified to do it with timing marks aligned ? - with timing marks aligned, I would have 6 out of 8 ports at zero lift - right side would be under no tension and left side would have two valves under tension. Any idea why Subaru does recommend it - it would be a lot easier!

3) I measured clearances in .001 inch increments - stupid of me - I should have done mm. Now, I will change shims if they are off by .002 inch or more. Subaru recommends redoing them if they are off my more than .02 mm which is slightly less than .001 inch (.025mm). My question is on replacement shims. For example, if intake value is at .006 inch(.008 inch is recommended clearance ) and current shim size is 2.55mm, what new shim size I should get? In theory .006 inch could mean that I am off by anywhere from .03 to .05 mm. Should I get a 2.55 - .03 = 2.52mm or 2.55 - .05 = 2.50 mm shim? I am leaning towards 2.50, since valve clearances reduce with time. So if I overshoot by 2mm, it will reduce over time...

4) Measuring shims - on most of them I can read numbers on current size, shim size doesn't change with age, do they? Do I need to remeasure them?

5) Can shims be ground down with sandpaper or other thing to reduce their current thickness? So can I convert 2.55 to 2.50 somehow? Local dealer wants 10 bucks for each! They are 4.60 at 1stsubaru, but I would have to wait a week!

#2 sea#3

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Posted 19 December 2004 - 05:56 PM

[/color]

 

[color=black]2) When putting in new shims, to double check the clearance, can I just do it with timing belt OFF with values at "zero lift"? [/color]

 

[color=black]
Yes you can but I would suggest you only do 1 cam at a time , so that you don't bend any valves ( the intake and exhaust valves will interfere with each other when rotated incorrectly ) Just rotate the cam lobe of each valve you are measuring at the time and position it at the "zero lift" position


3) My question is on replacement shims. For example, if intake value is at .006 inch(.008 inch is recommended clearance ) and current shim size is 2.55mm, what new shim size I should get? In theory .006 inch could mean that I am off by anywhere from .03 to .05 mm. Should I get a 2.55 - .03 = 2.52mm or 2.55 - .05 = 2.50 mm shim? I am leaning towards 2.50, since valve clearances reduce with time. So if I overshoot by 2mm, it will reduce over time...

If you look on the hood of the car there should be a placard that gives you a range for valve clearances . Ideally you want to shoot for the mid range clearance


[/color]

 

[color=black]So if I overshoot by 2mm, it will reduce over time...[/color]

 

[color=black]
I hope you mean 0.02mm . I think that would be within the range


4) Measuring shims - on most of them I can read numbers on current size, shim size doesn't change with age, do they? Do I need to remeasure them? 

i wouldn't go by what’s on the shim because they do wear down . If you do everything within spec you shouldn't have to touch the valves for 100.000 miles


5
) Can shims be ground down with sandpaper or other thing to reduce their current thickness? So can I convert 2.55 to 2.50 somehow? Local dealer wants 10 bucks for each! They are 4.60 at 1stsubaru, but I would have to wait a week!


Don't sand them, bite the bullet and get it right the first time . Don't want to burn a valve and do it all over again



SEA#3

#3 bearbalu

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Posted 19 December 2004 - 11:35 PM

Thanks. Yeh, I meant .02 mm! The midrange is 2mm (.008 inch) intake and .25mm ( .010 inch) exhaust with .02mm (001 inch) tolerance. The trouble comes when one uses inches to measure. So .006 inch clearance can be anywhere from .15mm to .17mm. Replacement shims would have to be smaller by 5mm to 3mm..

BTW, I remeasured the shims - they haven't changed in size.

What problems can sanding down the shims from 2.55 to 2.50 create?

#4 Gnuman

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Posted 19 December 2004 - 11:59 PM

Thanks. Yeh, I meant .02 mm! The midrange is 2mm (.008 inch) intake and .25mm ( .010 inch) exhaust with .02mm (001 inch) tolerance. The trouble comes when one uses inches to measure. So .006 inch clearance can be anywhere from .15mm to .17mm. Replacement shims would have to be smaller by 5mm to 3mm..

BTW, I remeasured the shims - they haven't changed in size.

What problems can sanding down the shims from 2.55 to 2.50 create?


We will start with the removal of protective coatings, and move quickly into having a shim that is 2.51 on one end and 2.54 on the other. . . In order to sand the shims down, you would have to do it perfectly, and te dificulty in that is far more than coughing up the cash to get the precission milled ones from Subaru. . .

#5 bearbalu

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Posted 02 January 2005 - 02:56 AM

Okay, I bit the bullet and bought these for 7 bucks a piece...

I measured the clearances with timing belt off - seemed to work fine.
I am still curious as to why Subaru doesn't recommend measuring clearances with timing marks aligned - one could measure 12 valve clearances in this position.




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