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View Full Version : Valve Shim Clearance???



Derek
04-04-2006, 10:06 PM
I was talking to a guy today that has been working with sr20's for a long time, and I told him that I had gotten a valve job done at a local machine shop. He then told me that I must adjust my valve shim clearance, otherwise I could risk breaking a rocker arm due to the increase in valve stem hieght. Is this true? I checked the owners manual and I did not really understand the procedure. He said that he used emery cloth to polish down his shims to get them where they needed to be. I was just wondering how u know how much to take off. Do you measure the distance from the top of the valve stem the the top of the spring retainer and then make the shim that same thickness? Could someone with any experiece with this please clarify this for me? Thanks. -Derek

97 S14
04-05-2006, 12:23 AM
Relax, SR's have hydrolic lifters so no need to worry about lash.

jjanko
04-05-2006, 04:50 AM
How can you say there is no need to reshim? The FSM specifically states the tolerance which is .08 in and .1 ex. A valve job will definately change this. I would know since I actually had mine checked afterwards.

jjanko
04-05-2006, 04:52 AM
I was talking to a guy today that has been working with sr20's for a long time, and I told him that I had gotten a valve job done at a local machine shop. He then told me that I must adjust my valve shim clearance, otherwise I could risk breaking a rocker arm due to the increase in valve stem hieght. Is this true? I checked the owners manual and I did not really understand the procedure. He said that he used emery cloth to polish down his shims to get them where they needed to be. I was just wondering how u know how much to take off. Do you measure the distance from the top of the valve stem the the top of the spring retainer and then make the shim that same thickness? Could someone with any experiece with this please clarify this for me? Thanks. -Derek



Your best bet is to take it to a shop that knows how to do it. If you don't know one call your local Nissan dealer and tell them you have a sr20 head that needs to be shimmed. They should be able to direct you to whatever shop they use. Or you can rent the tool, there is a guy on this board that rents them. I don't suggest this since there a lot of room for error. I actually got the tool and tried to do it myslef but wasn't confident with the results I was getting. In the end I paid a shop to do it.

a2low240
04-05-2006, 07:25 AM
You have to make sure the valve stem total height is the same within .001in. (factory spec) othersise the rocker will push down one valve before the other. ( higher (stem + keeper/shim) one ) The idea here is to make the valve stems the same height so that the valves are opened at the same time. If the valve strain is not shimmed correctly you will end up with valvetrain noise and the increased risk of throwing a rocker arm at higher rpms. The last thing you want in the valve-train is the rocker arms moving any other way but up and down.

BTW. We rent the tool.

forcefedS13
04-05-2006, 09:44 AM
shimming should be universal. thats my opinion. my machinist has my head right now, and they arent doing it specifically by the FSM. I complained that it says it "has to be done to these specifications"

His reply was: calm down, ive been machining heads for 40 years...its all the same. Its just common sense.

HMMMMMMMMMMM.....

Big_Bronze_Rim
04-05-2006, 10:52 AM
You definitely need to measure for the proper shim thickness. Like Matt mentioned, if you dont get it right you it will try and push one valve open before the other and eventally break the rocker arm. When we did my freinds head we had the machine shop at his work make a tool that fit into the HLA hole just like the factory tool. If you cant have one made, I'd rent it. Regardless, if you have valve work done, its not really an optional step. Plus I dont really like the idea of "filing" down the stock shims. Just measure what you need and order the right stuff from the dealer, then you know you got it right.

gt3071r240
04-05-2006, 12:01 PM
I know you can rent the tool from matt at import intelligence, as i recently did, I would highly recommend it. It was very easy to use, and provided the needed flat reference point for mounting the dial indicator when measuring. I do not understand how your machine shop would be meausring this without the tool. I am enrolled in the siu autotech school and was present when our engines teacher chewed the machine shops ass out for trying to sand down the shims on a toyota head that we were working on, he said that they were coated and had to be replaced with the proper size not sanded. this of course was cam over shim design not utilizing the rocker arm.

Big_Bronze_Rim
04-05-2006, 12:21 PM
he said that they were coated and had to be replaced with the proper size not sanded. this of course was cam over shim design not utilizing the rocker arm.



You make a good point. Whether or not they are coated, they act as a bearing surface and Im sure require a proper surface finish to prevent galling or scoring of the rocker arm pad. I know mine are almost mirror shiny. Please don't sand rocker arm shims.

wootwoot
04-05-2006, 02:47 PM
shimming should be universal. thats my opinion. my machinist has my head right now, and they arent doing it specifically by the FSM. I complained that it says it "has to be done to these specifications"

His reply was: calm down, ive been machining heads for 40 years...its all the same. Its just common sense.

HMMMMMMMMMMM.....





whats this guys background with machine work? Import or domestic mostly? A lot of the big v8 guys can barely do [censored] to our motors.
Reguarding the "sanding" of the shims, just put it on a surface grinder then http://forums.freshalloy.com/images/graemlins/wink.gif
any good machine shop has one and then it isnt very hard to have parts coated, just take its thickness into consideration too...

240Shorty
04-05-2006, 04:05 PM
DONT GRIND your shims, just do it right. Rent the damn tool from Matt(importintelligence). He will give you a lot of extra shims, of all different sizes. Yopu just take what you need and give him yours to replace those you took. If your machine shop is real good he can whack the tips of the valves, as long as its with-in tolerance, and even them out. Renting the tool is only 45.00. do it. also the shims arent necessarily "coated" i think they are just polished to perfection.

Derek
04-05-2006, 04:35 PM
Thanks for all of your help guys. I think I will rent that tool and do it myself. The only thing is that I still dont understand how you are supposed to determine what shim/ rocker arm retainer thickness you should use. Where do you measure? What do you subtract to find out the thickness? In the FSM, it looks like you measure from the groove in the rocker retainter, then to the top of the valve, and subtract those readings....but then wouldnt you just be measuring the retainer/shims that you already have??? Sorry for being so retarded, but could someone please explain this to me? Thanks. -Derek

b18c_ferio
04-05-2006, 04:43 PM
Thanks for all of your help guys. I think I will rent that tool and do it myself. The only thing is that I still dont understand how you are supposed to determine what shim/ rocker arm retainer thickness you should use. Where do you measure? What do you subtract to find out the thickness? In the FSM, it looks like you measure from the groove in the rocker retainter, then to the top of the valve, and subtract those readings....but then wouldnt you just be measuring the retainer/shims that you already have??? Sorry for being so retarded, but could someone please explain this to me? Thanks. -Derek

i think that the shim is supposed to be at the same height as the bottom of the "slot" on the guide shim/slotted shim..notice in the fsm the line across the top of the shim and the bottom of the "slot", i think these heights have to be the same

forcefedS13
04-05-2006, 08:18 PM
i just checked the FSM, and it states:

+0.025mm (0.0010 in)
shims are available in thickness from 2.800mm (0.1102in) to 3.200mm (0.1260in) in steps of 0.025mm (0.0010 in)


im taking this to the machine shop tomorrow rockin the "mad" face. we'll see if he agrees with this or not.

Derek
04-05-2006, 10:04 PM
So, pretty much you are just matching a shim to get the other valve height (with the shim installed) within .001" of the rocker guide slot, and shim size may vary from cylinder to cylinder?

240Shorty
04-05-2006, 10:07 PM
you are correct. you want the middle of the grooved shim to be the same height as the smooth shim. that way the rocker arm sits perfectly level.

Derek
04-05-2006, 10:18 PM
ok, cool....thanks again everyone, for your help. I will keep you guys posted on how my car is coming along. thanks again. -Derek

a2low240
04-06-2006, 09:21 AM
Just for a little backround info, Kent Moore ( designer of tool for shimming SR heads ) has changed the design of the tool from a tool that sits in the HLA hole to a plate that bolts on top of the head ( like we rent ) They changed the design because they said that the tool that fits in the HLA spot is not accurate enough due to flex in the armature.

These things are very sensitive to work with and measuring specs to .001 is NOT for your "been doing heads for 40 years on v8's." These are tolances that old skool machine shops thorw out the window.

If you trust old skool machine shops that are thick headed and that do not adapt to new standards then your SR will run like a carb'd v8 missing 4 cylinders.

As they say, your motor is only as good as the person who built it.

forcefedS13
04-06-2006, 09:38 AM
thats funny http://forums.freshalloy.com/images/graemlins/iagree.gif

I printed out the FSM directives for shim measurement and clearence. Im taking it to him in about an hour. He tends to argue with me about everything, and says i have no clue what im taalking about...yet hes never heard of an SR20DET!

I think i may have made a mistake by bringing the head to him, we havent even agreed on a price yet, so we will see how he reacts to my research.

forcefedS13
04-06-2006, 12:54 PM
It didnt go to well, he argued with me about how it doesnt matter if one valve opens one millionth of a second before the other. He measured them right in front of me to humor me and it showed the slotted shim at 0.114 and the smooth shim at 0.116...2 thousandths off. He said that wouldnt matter. Im not too sure aabout that. 2 thousandths is not worth tollerating if its SUPPOSED to be equal.

His other arguement is that the cam lobes dont measure out evenly either..they never do, so why would it matter.

jjanko
04-06-2006, 03:01 PM
Maybe its time to find a new machinest that will do what you are paying him to do.

Brad
04-06-2006, 03:52 PM
i can kinda see both sides of the argument. but then again nissan engineers put that stuff in there for a reason. they arent just trying to be funny or make you do pointless work. its a gamble to do it your machinist's way, but its up to you

forcefedS13
04-06-2006, 04:19 PM
I dunno, 2 thousandths isnt alot to really machine for. i could just polish it with some emery clotch and call it a day. Im doing the same with the rocker arm cam lobe surface.

LLmod
04-26-2006, 04:13 PM
forcefed, I dont know much about sr20's but your machinest is right about cam lobes sometimes not being equal. I dont think that it matters from.114 to .116 unless one of those #rs are out of spec. thats tooo little of a difference to say that the valves wont open at the same time. there are tolerances/margins that you have to fit into. and someone here said somethin about the machinest that didnt even know what an sr20 is....who cares? how would that affect their ability to machine? btw, hope everything came out ok. let use know.