SR20 Dual Guide Conversion

[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?

https://scontent.fsnc1-1.fna.fbcdn.net/hphotos-xpt1/v/t1.0-9/12552624_10153288139326657_1287570880750381297_n.j pg?oh=d304beee45e23553ff2aa6cf1938729f&oe=5706BD6A
https://scontent.fsnc1-1.fna.fbcdn.net/hphotos-xfp1/v/t1.0-9/12541150_10153288139311657_5437868032033756270_n.j pg?oh=21b8e8a91c4d2d18c2b07732ccfe399f&oe=5730D1ED

[jr_ss]

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

[Options13]

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

[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]

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

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.

[tunermt]

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.

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 (www.brewedmotors.com) with the rockers/valves all within spec.

[Options13]

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

[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.

[smartoss]

You can get different thickness guides from Tomei. http://www.frsport.com/index.php?target=catalog&mode=searchImproved&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.

[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.

https://scontent.fsnc1-1.fna.fbcdn.net/hphotos-xlf1/v/t1.0-9/12524056_10153291584611657_4607420716432428796_n.j pg?oh=ff659f4e8789b82ef10fc63efd78712e&oe=57462445

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

[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.

http://www.sr20forum.com/img/data/6358/IMG_2743.jpg

[jr_ss]

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.

http://www.sr20forum.com/img/data/6358/IMG_2743.jpg

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.

[pTen]

*helps prevent

[jr_ss]

*helps prevent

Yes, thank you.

[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


Sent from my iPhone using Tapatalk

[R3cK]

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.

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

[jr_ss]

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

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.

[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.

Sent fra min C6603 via Tapatalk

[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..

[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!!!

[Tyler_240]

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!!!

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.

[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.

[Options13]

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

[jr_ss]

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

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.

[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

[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....

[TomBec]

good info.. thanks for the input. read through it a couple times before putting my head back together today. was very careful with oiling/torquing everything and it runs great (so far). ended up going with oem guide shims all 'round. the motor even idles a little quieter.. i will update here if i throw another one.

[Tyler_240]

Nice...I got my top end back together yesterday and on the road after swapping in the new guides and bleeding the lifters really good...I removed my RAS and swapped in the OEM Oil Baffle and all my lifter chatter is gone...i've run the motor up to 7K RPMs with no issues.

[TomBec]

Forgot to mention I also removed ras and baffle.

[sidewaysil80]

Bumping this because I have a simple question. When performing the dual guide conversion, you need to buy 8 of Nissan p/n 13218-53J00 (guides). I get the concept of needing to machine down the "new" guides to match the "old" guides so the rocker stays level, but wouldn't it be possible to just simply replace all 16 guides at once? That way they are 100% level with each other and you are effectively “resetting” the rocker to cam clearance? Or would that make that clearance to tight?

[tb13]

Bumping this because I have a simple question. When performing the dual guide conversion, you need to buy 8 of Nissan p/n 13218-53J00 (guides). I get the concept of needing to machine down the "new" guides to match the "old" guides so the rocker stays level, but wouldn't it be possible to just simply replace all 16 guides at once? That way they are 100% level with each other and you are effectively “resetting” the rocker to cam clearance? Or would that make that clearance to tight?

You can't just replace all 16 because the valve heights are more than likely not level. If you have your machine shop set your valve heights all perfectly level, you can just run a 3mm on each valve. 99% of engines will require different size shims on each valve because they are not the same height.

[sidewaysil80]

I think I got it. The FSM says replace all guides when servicing head because they are uniform in size. The shims, if kept, are offered in various sizes to compensate for valve height and match guide.

If replacing both guides they would be same thickness but whatever valve height is won’t be compensated for like it is with the various thickness of shims.

Thanks for saving me $50 bucks lol!

[tb13]

I think I got it. The FSM says replace all guides when servicing head because they are uniform in size. The shims, if kept, are offered in various sizes to compensate for valve height and match guide.

If replacing both guides they would be same thickness but whatever valve height is won’t be compensated for like it is with the various thickness of shims.

Thanks for saving me $50 bucks lol!Exactly. I believe from Nissan the motor should have 3mm shims to match the 3mm guides, but over time the valve stem can wear which is why different thickness shims are necessary for valve adjustments in used motors.

I know some guys have had success just dropping guides in, but it's probably better off doing it right the first time, measure it all up and then order Tomei guides in the correct thickness.

Sent from my ONEPLUS A5010 using Tapatalk

[sidewaysil80]

Exactly. I believe from Nissan the motor should have 3mm shims to match the 3mm guides, but over time the valve stem can wear which is why different thickness shims are necessary for valve adjustments in used motors.

I know some guys have had success just dropping guides in, but it's probably better off doing it right the first time, measure it all up and then order Tomei guides in the correct thickness.

Sent from my ONEPLUS A5010 using Tapatalk

Okay great. I can get OEM guides for $4 each so I'll just order eight and grind them as needed. I'm thinking between the dual guide rocker arm conversion, roller rocker sr20de hydraulic lifters, and new valve springs I should have no issue reaching 9K rpm. I have been doing a lot of research of the sr20 forum since they have essetinally pioneered the n/a sr20 and a lot of these tips and tricks have been tested over there.

[TheRealSy90]

Pretty much. Dual Guides, RR lifters, good to go.

OptionS13 i'm pretty sure you didn't do something properly with the issues you had.

[tunermt]

Few tid bits from the bottom of the article to help choose your cams:
https://brewedmotors.com/blog/sr20det-dual-guide-shim-rocker-arm-conversion-tomei-poncam-install.html
"There are a large range or cam specs available for the SR20det ranging from 256 duration with 11mm of lift all the way up to over 285 duration and 12.5mm of lift for high rpm builds. Tomei has proven time and time again to make GREAT cams for the SR20det that deliver big gains and when matched with some mild head work/port n polish we see huge gains throughout the entire RPM range as well as a faster spool time from the turbo. We have also noticed the center line on the Tomei cams is VERY close to stock which means you can actually bolt these cams in with stock cam gears and see good results. Many other aftermarket cams will require a good amount more adjustment compared to the Tomei cams to "degree the cams" into spec.

-Tomei 256 Pon cam: These are the perfect cams for an otherwise stock SR20DET good mid range, smooth idle and can even work with the stock ECU.

-Tomei 260 pro cam hydrolic lifter: These cams are good for a small turbo build looking for decent idle and strong power from 3500-7000 rpm. **aftermarket springs and retainers should be used**

-Tomei 270 pro cam hydrolic lifter: These cams are good for a medium sized turbo build looking for decent idle and strong power from 4000-8000 rpm. **aftermarket springs and retainers should be used stock wont hold up well here**

-Tomei 280 pro cam solid lifter: These cams are good for a mid-large turbo build looking strong power from 4500-8500 rpm. **aftermarket springs and retainers must be used**​"

[tunermt]

Bumping this because I have a simple question. When performing the dual guide conversion, you need to buy 8 of Nissan p/n 13218-53J00 (guides). I get the concept of needing to machine down the "new" guides to match the "old" guides so the rocker stays level, but wouldn't it be possible to just simply replace all 16 guides at once? That way they are 100% level with each other and you are effectively “resetting” the rocker to cam clearance? Or would that make that clearance to tight?


You need to make a tool to measure and correctly set the clearance. Any other method is just guessing as close as you can. Just measure once and do it right after all your going dual guides to not worry about the shims and rockers any more.