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SE-R Driven
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Discussion Starter #1
When shimming valves in my SR20DE after having valve job on the head, I understand that the reason is to ensure the rocker arm will sit squarely against the lobe on the cam... I've started doing this, but have found that between shimmed valve pairs ... there is a difference in height.

1)Does it matter if the heights of the shimmed valve pairs is different afterwards?....

2)Will this difference somehow be made up by the hydraulic lash adjusters? I assume they will, but do not quite understand how they work.

3)Also does anyone know where to purchase shim's and rocker arm guides other than a Nissan dealership?

Any help would be much appreciated... Thanx:cool:
 

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The valve stems will end up at different height, but you use different shim thicknesses left and right of each cylinder inlet and exhaust to bring the net height balanced. Does that now make sense?

Mike
 

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SE-R Driven
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Discussion Starter #3
UK-SRi said:
The valve stems will end up at different height, but you use different shim thicknesses left and right of each cylinder inlet and exhaust to bring the net height balanced. Does that now make sense?

Mike
Yep, already understood that.... and appreciate the feedback.... let me illustrate.

What I have: #1 cyl exhaust valves shimmed and heights balanced, and the same for #2 exhaust... but when comparing the finished heights of #1 exh valves with the finished heights of #2 exhaust valves..... #2 are .005 taller.

I am using the kent Moore shimming plate to shim the engine... so I can shim 4 pairs of valves with the plate bolted on. .... but after I'm done, and out of curiousity, I zero out the dial indicator on one of the pairs of shimmed valves .... and then check the other 3 sets of shimmed valves..... just to see how close they are to each other..... I get variances from .001 to .007 in. ... .in shimmed height from one pair of valves to the next....

Just trying to find out if this is an issue, or something that the hydraulic lash adjusters will compensate for?? :cool:
 

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Premium Member
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Its not the height of the valves that are important in relation to each individual cylinder.

But the shimmed height of the two valves per cylinder thats important. The lash adujsters will accomodate the difference between all 4 cylinders.

Best to use nissan shims, and rocker arms...not cheap but made for the motor.
 

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Stackdaddy said:
When shimming valves in my SR20DE after having valve job on the head, I understand that the reason is to ensure the rocker arm will sit squarely against the lobe on the cam... I've started doing this, but have found that between shimmed valve pairs ... there is a difference in height.

1)Does it matter if the heights of the shimmed valve pairs is different afterwards?....

2)Will this difference somehow be made up by the hydraulic lash adjusters? I assume they will, but do not quite understand how they work.

3)Also does anyone know where to purchase shim's and rocker arm guides other than a Nissan dealership?

Any help would be much appreciated... Thanx:cool:
Yeah, when u got the 2 valve tips leveled, the hydro adjuster takes care of all the clearance. I get my shims form the junkyard, but you can buy ones fromm the dealershop for around 8 bucks. They sell u used ones, dunno why. I thought they would have new ones. That is why I just get junkyard ones now
 

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SE-R Driven
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94 Posts
Discussion Starter #7
OK, Folks.... appreciated the solid answer....

And I found in other posts on the subject, that Mossy also sells the shimms....
I already spoke w/Greg today.... to get what I need.... Thanx
 

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Professor Dingbat
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5,543 Posts
Just to add to this, a rocker arm establishes a wear pattern on the shim and vice-versa. It would be best to keep the same shims with the same rocker arms, but if you have to re-shim, you should by rights buy all new shims and rocker arms. You could probably get away with the used ones.

When I built a DE head for a race motor, I bought all new shims and rocker arms. $300 is cheaper than DNFing and replacing the valves and the pistons.
 

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SE-R Driven
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Discussion Starter #9
FastNX said:
Just to add to this, a rocker arm establishes a wear pattern on the shim and vice-versa. It would be best to keep the same shims with the same rocker arms, but if you have to re-shim, you would have to buy all new shims and rocker arms. You could probably get away with the used ones.
Well then..... if I'm installing new cams, and having to reshim the valves.... I was not aware that new rocker arms were a must. My original rocker arms, look to be in great shape... with no serious wear, pitts or other marks on them... so are they not usable?:(
 

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AWD owns me
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You can reuse the shims and rockers.
 

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Professor Dingbat
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You CAN re-use them. There may be a slight increase in safety in getting all new parts. The motor I built had C3 cams and was meant to spin from 5000-8000RPM for 3 hours at a time. For a street application with smaller cams, you could probably get away with used stuff.
 

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SR20DE stock G20 p10 highport
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MY QUESTION: My current (SR20DE) stock cams have pitting on their lobes. I have cleaned out the oiler tubes (let them soak with carb cleaner inside). I want to replace the camshafts.
Given that they are pitted, I take it the rocker arms should be replaced, as well. I am looking to find a donor head and use its rocker arms and shims in place of my current ones. Do I have to use the cams from the donor head, or could I use an aftermarket set of cams with the donor rocker arms and shims? Can I use a set of hydraulic lifters I pulled from a junkyard SR20DE, or MUST I use the original ones in my car. The ones I pulled are newer and have a smaller hole on top, which I understand is the updated version.

I read in the thread ROCKER ARM AND SHIMS QUESTION that it is NOT advisable to switch out a set of rocker arms and their corresponding shims in order to use these in a head whose rocker arms and shims had gotten mixed up. After reading the present thread, I have the understanding that it is alright to do this when installing a new or replacement cam, so long as it is for a street car, but not alright to do if the application is a race engine (higher rpms on a regular basis).
The member's question was "can I just take the shims and rocker arms off another sr20 head in order and put it in my car in the same order?"

Is it that the rocker arms, shims AND CAMS MUST all come from the SAME head if non-original rocker arms/ shims are to be used at all with the new cam?

If so, Why then do camshaft manufacturers advertise "drop-in" or "bolt-on" cams that they claim are "compatible with stock valve trains" and "require no adjustments me made?
Is it just understood that when installing a new camshaft, the new cam's lobes are going to wear down a bit in order to match the shape or level of the existing rocker arms? (assuming no re-shimming is required?)
Or, is it ALWAYS NECESSARY to re-shim when a new CAMSHAFT is installed in place of a damaged one?
 
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