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My 91' Sentra 2.0L SE-R broke a rocker arm, I ordered the rocker arms needed, but when i took apart the vavle cover, i noticed that one of the valve shims from the broken rocker arm seemed to be missing. I looked pretty much everywhere in the engine for it (without completely taking it apart), but no luck. So i went to the dealership to see if they could order me the part. Aside from not knowing anything about the part I needed, he told me there was only 1 part number for it, but around 23 sizes. The rocker arm sits upon 2 metal shims, one is universal for every valve, but the other seems to have different sizes and weights.
So what I am asking is , should I take off another rocker arm and measure the size of that valve shim, or is it different for every individual valve. I would also like to know of any good sources for a blowout of the 91 sentra se-r 2.0 engine. I'm not a genius at all when it comes to cars, so I need as much guidance as possible. Thank you to anyone who responds, this is VERY important to me. If needed,ask me any questions to help you understand my problem more clearly.
 

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so you need a valve shim for an sr20de? id try a junk yard first.
 

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Discussion Starter #3
the problem is, there seems to be a lack of sentra's in the pick n' pulls I've been to. Especially the 2.0 engine types.
 

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The thickness of the shim is critical. It is the way the valve train is adjusted for the proper clearance, and each shim is measured separately. The thickness depends on how high the end of the valve stem is above a reference point.

Determining the correct thickness requires a special tool, a plate which bolts onto the cam journals and is the reference point for measuring the valve stem height. The last time I checked, the tool was several hundred dollars. It also requires a special adaptor for a dial indicator for the measurement.

I would redouble my efforts to find the shim. You may have to remove the cams. Also, if you are unlucky, it may have dropped down the holes in the front where the chain runs, and is in the oil pan.

Lew
 

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Is the shim thicknes really so critical? Becouse the SR20 has hydraulic adjustable valve clearance. But I would not drive around with some loose metal parts in my engine :)
 

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p10driver said:
Is the shim thicknes really so critical? Becouse the SR20 has hydraulic adjustable valve clearance. But I would not drive around with some loose metal parts in my engine :)
There must be contact between the rocker arm and the shim and hydraulic lash adjuster at all times (Factory specification < 0.001"). If the shim is too thin, then there will be no contact when the valve is closed. This will cause valve train noise, and torsional stresses on the rocker arm (contact on one shim and not on the other).

Lew
 

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lshadoff said:
The thickness of the shim is critical. It is the way the valve train is adjusted for the proper clearance, and each shim is measured separately. The thickness depends on how high the end of the valve stem is above a reference point.

Determining the correct thickness requires a special tool, a plate which bolts onto the cam journals and is the reference point for measuring the valve stem height. The last time I checked, the tool was several hundred dollars. It also requires a special adaptor for a dial indicator for the measurement.

I would redouble my efforts to find the shim. You may have to remove the cams. Also, if you are unlucky, it may have dropped down the holes in the front where the chain runs, and is in the oil pan.

Lew
If you cant find the shim I suggest you buy the thinnest size, install it and measure the clearance with feeler gauges.Do not run the car, the clearance will be way off.
Calculate the correct size needed, purchase and install. You can then run the car.
This measure and adjust technique is used on older DOHC engines like the Jaguar's at 60,000 mile intervals, and it works. Been there, done that.
I would add a caution to re-check after a 1,000 miles to make sure all is well.
This gets round the need for the expensive tools.

But I just read there is a hydralic lash adjuster, so I dont know if this will work. The lash adjuster needs to be in the middle of its range approx for proper operation, and the technique I described above will not do this because you dont know where the lash adjuster is.
 

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where the lash adjuster is......if you dont know where that is we have a problem.....oh and they arent "adjustable" in height.....they are self adjusting hydraulic units, they dont have a precision height, they just sit in their holes and are left alone until they need to be bled of air. i suggest you all join sr20fourm.com and ask your questions there, the members are all well informed of how the sr works, and can help you out with your problem.
 

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92redwhiteandblue said:
where the lash adjuster is......if you dont know where that is we have a problem.....oh and they arent "adjustable" in height.....they are self adjusting hydraulic units, they dont have a precision height, they just sit in their holes and are left alone until they need to be bled of air. i suggest you all join sr20fourm.com and ask your questions there, the members are all well informed of how the sr works, and can help you out with your problem.
You should read the Factory Service Manual. The valve train IS adjustable using shims of various thickness. This sets the correct preload on the hydraulic lash adjuster. The factory tolerance for selecting the correct shim thickness is 0.001" to set the correct preload.

Lew
 

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yeah i have a FSM, and a pair of nissan master techs that work in the same building as i do, along with a full nissan parts department. he said the lash adjusters had to be in the middle of their range.....the lash adjuster has no range.
 

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92redwhiteandblue said:
yeah i have a FSM, and a pair of nissan master techs that work in the same building as i do, along with a full nissan parts department. he said the lash adjusters had to be in the middle of their range.....the lash adjuster has no range.
OK please read what Lew has written in the previous post.

So what you have is a hydraulic lash adjuster just like on the American V-8's but in a different place.
This has to be in the middle of its adjustment range. It adjust automatically using oil pressure.

The shims do this initial adjustment or "preload"

Please believe us here, this is correct.

Good Luck.....
 
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