Options13

There isn't much information on this subject... Curious why?

Either way what exactly are the steps to this?

I shaved all my rocker arms to fit a dual guide on both sides.

One thing i know is that guides are all the same size, unlike shims.

So, does the rocker arm its self have to be shimmed to size, or do i just slap the guides in and rock and roll?

Or is there a way to stick a feeler gauge between the cam and rocker arm to test clearances?

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jr_ss

All the guide shims are the same thickness. There's no adjustment for them.

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Options13

so then it would be required to shave the rocker arm down to spec?

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Driftzenki

when I did my conversion I made sure they were max .003 of an inch apart from each other with a dial indicator and custom tool that goes inside lifter hole, haven't given me any problems since, may have to switch guides around due to normal wear

jr_ss

You don't shave anything. The rockers are modified for the dual guide and then installed in the position they were pulled from. There no shimming or trimming, when this mod is performed. Install the cams and go. Now what might affect it is valve stem height. In which case, much more work would need to be performed.

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tunermt

You need to measure/adjust the rocker arm clearance same as a normal single guide SR.

The trouble is the guided shims only come in one thickness so you need to adjust the clearance another way (normally valve stem). Brewed Motors builds dual guide SR20 heads with the rockers/valves all within spec.

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Options13

i called mazworx, and they said to remove material off the rocker arm itself untill it is within spec.

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jr_ss

What is the "spec" though? As far as I can recall, there is no rocker to cam clearance spec in the FSM. It's strictly directed towards getting the rocker level to the cam lobe so that both valves actuate the same time and amount of lift. I don't have an FSM available to me ATM to clairify so, some one please enlighten me.

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smartoss

You can get different thickness guides from Tomei. http://www.frsport.com/index.php?tar...&q=Tomei+guide

Options13

Oh I might be mixing up my words, I mean, you may have to remove material off one of the guides to ensure that the rocker arm is level with the cam. I did more research last night, I feel like wet sanding the guide *if needed* to get the rocker arm level would be the best way comapred to grinding the rocker arm.

I'm going to try and mock up a tool today, by welding a stand to an extra hydralic lifter, so I can measure how thick I need the guide to be.

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Options13

So i was finally able to rig up a dial to measure all the size shims i need.

Unfortunately Tomei doesn't make a big enough guide for some of my valves..

Here's the size shims i need for each rocker arm.



would the best route, just to go to the dealership and find the closest shim i can to each measurement i can?

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R3cK

why would you do a dual guide?
just use one guide and one shim in the size needed.
measuring the size is pretty salty tho.

i let the work do by a person that made himself the measuring tool with a cnc machine. its basically a solid hydraulic lifter copy with the ability to mount this pressure measure clock thing. the problem is it never fits 100% tight so you have to constantly push it a bit to the shim points.

jr_ss

This modification basically prevents the rockers from kicking off in the event of bouncing off the rev limiter. It's a common upgrade to higher revving SRs.

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pTen

*helps prevent

jr_ss

Yes, thank you.

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TheRealSy90

Honestly, I've done dual guides in a bunch of sr20's by just throwing them in and going for it. The hydraulic lifter can usually handle the slight difference in shim height if there is one, as long as they are all fairly close.

Now, on my personal Sr i have the guide shims machined to match the thickness of each flat shim that it replaces, so that it maintains the exact same clearance.

It's up to you which way you do it. But every one I've done it to with just throwing them in and going has never had a problem, and never threw a rocker arm again. The difference in thickness is so minute.

I made a "How-To" video a couple years ago to explain this mod and how to do it, as most people don't know about or understand it. https://youtu.be/StxF9aLMoSg


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R3cK

interesting.
here in germany we just put RAS in and nothing bad ever happened.
never heard of dual conv. here.

jr_ss

Understood. The problem with RAS is they prevent the rocker from flying free and clear when they are tossed. This ultimately ends up with either broken rocker arms, bent valves, damaged pistons or all of the above.

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Trion

I have had dual guide shims for a couple of years now. The only right way to do it is to grind the guide shims to correct thickness. I never allow more than 0,02mm difference in clearance between cam and rocker arm.

When in need of thickness greater than 3mm, I use a shim (a thin washer) under the valve lifter as recommended by Mazworx.

I run it with tomei solid lifters and RAS. Never had any issues with throwing shims and rockers after installation.

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Options13

i ended up just ordering the proper sized shims for my head, but what kind of washers did you use trion? A standard washer with a hole in the middle of it ?

Once my shims arrive, i will be putting my head back together without the RAS.

I'm still debating on if i want to put stock lifters back in or run my after market ones..

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Options13

so my damn shims are back ordered for another week so i decided to just do the dual guide conversion.

What i did was shave the bottom of the guides till they were "level" with the other guides.

Now all my guides are either perfectly level with it's partner or within .001mm difference.

I'll put the head back together this weekend, and hopefully not throw any more guides!!!

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Tyler_240

Did you get everything back together? I noticed a few posts above suggested we can just throw the new guides in if we're using OEM valvetrain because they are all one size.

So did you "shave" your guides because you were running after market lifters?

Just wondering. I recently tossed a shim/rocker and I had RAS, and the rocker ended up riding on the spring retainer and i found the shim laying nearby...

I'm getting my rockers machined for the dual guides but want to confirm whether I need to measure the new guides or not.

I'm using OEM valves/springs/retainers/lifters/cams.

Options13

I did the mod, and I still tossed a guide, so I see this as a pointless mod... If you are throwing shims, something isn't right in your head..

I upgraded to jwt s4 cams, and I went back to stock springs and retainers. I had BC springs and if your springs are too stiff for hydraulic lifters it could be counter productive. Also all guides are the same size so it's hard to get the rocker "level" with the cams.. I went back to the standard guide/shim.

If there is enough movement in the rocker arm, you will still break the walls in the guides.. IMO this conversion isn't worth it.

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jr_ss

Try not beating the shit out of the rev limiter. That usually helps.

Also, no one said it was a fix-all for launching rocker arms. It helps prevent it. Perhaps you have more pieces out of spec than you initially presumed?

A fix-all would be swapping a VE head in.

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Options13

Funny thing is, I didn't hit rev limiter when I popped two rockers out.

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jr_ss

Then you have other issues you need to look into. There is no reason you should be launching rockers with upgraded springs and not bouncing off the limiter.

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Options13

My theory is that the springs that were in the head are too stiff for the hydraulic lifters, thus making it counter productive.

I'm going VVL now.. lol

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TomBec

im in the middle of the dual guide swap myself. i did some looking around and found a aussie company that manufactures SR20 shims to pretty much any size between 1 and 5mm. going to machine the rockers myself and order guide shims as close to the size of the pivot shims i can get. once i fish the rest out of my oil pan, of course.

might be worth checking out. http://www.precisionshims.com.au/

Dboyizmlg

^ or you could just order guide shims from the dealer.

I would go to Nissan race shop dealer, and order OEM

codyace

The thing that scares me/makes me question shimming in most cases are that most people have cheap measuring tools, in which i'd highly doubt accuracy. Atop of that, how many 'shim guys' are actually doing it "the right way"? Very few.

Lets also consider this: Your zillion mile SR has developed a wear pattern across the rocker top. You shim it properly, but now put new cams in. There's got to be a gradiant wear, and for sure a 'ramp profile' wear difference ya know? Also, how are you to account for rocker tip wear? Or across the 'pad' still being perfect?

Or lets say you got an engine that someone put FuckBoi Seat stomping springs and retainers in, lets say with a unknown shit cam that you now decide to change back to a 'stock' cam or a differnt brand? I wonder how many people even look at or consider looking at the rocker pad surface again?

So even with shimming...if you're not reusing the exact same 'combo' how can we really say it's evenly running against the cam surface? Sure the HLA takes up slack on the one end, and the spring deflection the other, but what's to say that the rocker pad itself is even, well 'even'?

Just some food for thought for those stressing out over it all. Do i have the tools? Yes. Have I shimmed them? Yes. But in other end, I've also not and never had an issue. IMO the biggest issue people have aren't freakin torquing it properly and tearing out threads or snapping cams.



So some things I've learned over the years

- I've had engines with yahtzee shim syndrome, slapped it all back together without shimming and they've gone thousands of miles without any lick of issue, or worry

- Dual guide conversion has been around forever. Know how many FWD guys just throw two in and role and never know the difference or ever have an issue? Like zero. 8000 rpm with a 'quality' cam, stock valvetrain, no worries

- I've even had track engines toss rockers and shims mid day. Put new shit in, and ship it. Problems? Never. End up spinning a rod bearing from the FWD pan sucking ass before anything haha.

In a perfect world with a good tool (like the CustomSteel one, or a good home made unit) on a bench with a good tool? Sure. But if you don't do it perfectly will it explode into a valvetrain fireball? Of course not. I'm sure my answer isn't 'perfect' but it's real world. It's not like we're building mechanical valvetrains here, we're still ultimately using a crappy hydraulic lifter....

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