Taesoo Kim (ILikeMy240sx)
Rebuild an SR20DET Cylinder Head
This is my biggest “HOW-TO” thread where I will show you how I prepare a “bulletproof” SR20DET cylinder head that you can rev to 9000 RPM+ if your bottom end can handle it.
I will show you how to disassemble a SR head properly, replace valve stem seals, upgrade valve springs + retainers, install aftermarket cams, install Tomei solid lifters and shim them properly, and how to assemble everything together properly.
All the work that I am doing to the head is with the head out of the motor. But you do pretty much the same thing except if you are doing this with it still attached to the block, you NEED to pressurize the cylinders so that the valves don’t drop.
List of parts that will be installed
1. Tomei Solid Lifters
2. Tomei 270/270 Solid Cams
3. Brian Crower Valve Springs
4. Brian Crower Ti Retainers
5. Fresh Valve Stem Seals
Ok here it goes…
The head that I will be working on
It is a little grimy and nasty… But the rocker pads and cam lobes are actually pretty shiny when cleaned.
Tomei Solid Lifters
Test shims/guides. These are sized 2.7 and 2.8mm (undersized a bit) so that you can properly measure the cam clearance.
Tomei 270 IN/EX Solid Cams
Here’s a picture of the spiffy new boxes they came in
Out of the box
Tomei cast bling
So notice how on the exhaust cam there is a longer dowel pin for RWD applications. BC cams did not have this
Look at how giant these lobes are on Tomei solid 270 cams
This is a side-by-side view of the stock cam and the new Tomei solid cam. Notice how much larger the lobe is compared to the stock one. Also, notice how the area under the curve for the solid cams is significantly larger than the area under the curve on stock cams – one good reason to get solid cams for solid lifters. More area under the cam curve, more power.
Here’s a side-by-side comparison of the base circles of the stock vs. tomei. Notice how the base circle is much thicker for stock cams (left) and thinner for solid cams (right). This is another reason to get solid cams when you are going solid lifters.
I’ve decided to switch cams to Tomei solid 270 cams as opposed to BC cams. But here are some pictures of BC 264s when I had them.
Brian Crower Stage 2 cams 264 duration and 12.05mm lift
It even came with Redline Assembly Lube. Sweet.
Redline Assy Lube
Brian Crower Valve Springs + Titanium Retianers
Stock spring to the left. BC to the right.
BC spring is considerably stiffer than the stock unit. I can barely compress it when I try it with my fingers. Also notice that stock spring’s top and bottom (green paint) are shaped differently but BC unit is the same. This means you can install this with no specific orientation unlike the stock ones.
Stock retainer to the left. BC to the right.
The BC unit is much lighter than the stock. I measured the both with a caliper and they are both with-in .001″ of each other except for the retainer height. There was about .015″ of difference where the BC unit was shorter.
Valve Stem Seals
Ones in the baggie are the intake ones and the ones in the blue packaging are exhaust ones. If you want to order them, intake ones get it from 91 Nissan Sentra and the exhaust ones you can get from any DOHC KA.
This is why int & exh valve seals are different.
Exhaust valves are filled with sodium. Hence thicker.
DISASSEMBLY Part 1
Now let’s start taking things apart. But before you do… EVERYTHING THAT YOU TAKE OUT MUST GO BACK IN THE SAME PLACE. I can’t stress this enough. This includes Cam caps, rocker arms, shims, rocker guides, lifters, valves, etc etc Unless you are going to re-shim everything this is VERY VERY important. I am going to re-shim everything due to going solid lifters but if you are not you need to keep that in mind. But regardless, cam caps must be in order.
If you haven’t already done so, mark your cam caps if there are no markings already. Mine came makred with 2,3,4 as shown below so this makes things easier for me but I’ve seen many cam caps that do not come marked like that.
Start loosening things in the order shown below.
Take the cams out by simply lifting on them. You might have to pry it out if it’s stuck.
Now take the rocker arms out along with rocker guides/shims and lifters. Once again, keep them in order.
Using a magnetic wand on the shims makes it alot easier to take them out.
Sometimes, lifters are very stubborn to come out. Gently, pull it with a plier. I stress gently.
Everything in Order. For some reason, this head was missing a rocker arm and everything else on 3rd exhaust bank. This is not a big deal for me as I need to re-shim everything. So all I have to do is buy a new rocker arm and shim.
Everything is in a labeled bag. For example, Rocker arm+rocker guide/shim + lifter that came out of the 1st bank of the exhaust size is labeled with E1 and so forth to help me keep track of where it came from. I do not need to do this for this head but you need to if you are re-using those parts.
The head as it sits now…
DISASSEMBLY PART 2
There are many tools available for removing valve springs but here are two that I have. Other ones just take too much effort to get them to work. The one you see in the red box is from Snap-on and the one on the bottom is from Matco but Snap-on also sells them.
The small tool is composed of two pieces.
Removing Valve Springs
First, stuff a tower underneath the valves that you are working on so that the valves do not move. If you are doing this with the head still on the motor, you NEED to pressurize the combustion chamber so that the valves don’t fall down.
So, to use the small tool, take only the silver part of the tool and put it over the retainer.
Then give it a good wack with a rubber mallet as shown. Please dont use a hard surface hammer as that will damage the tool. You might have to give it multiple hits because sometimes only one valve keeper will come out.
You can also push on the tool very hard. Its more effective when you push but requires more strength and effort.
When both valve keepers come off, you will see this because the end of the tool is magnetic.
Take the retainer off and inside you will see both keepers.
Now I will show you how to use the snap-on tool. (MY RECOMMENDATION)
First remove the 1st and 5th cam caps from both the intake and the exhaust side as shown.
Install one end of the leg with supplied bolts and washers.
Install the other end of the leg but do not tighten the bolts yet.
Insert the bar through the top holes and align the left leg so that the bar is straight. Now tighten the bolts on the left leg.
Assemble the remaining pieces as shown. I found number 2 hole to work the best
Use the bar and put the tool on top of the retainer like this
Now grab the handle and push down hard. Compress until the keepers are loose like this.
Take a magnetic wand and get the keepers out.
All springs taken out on the exhaust side.
DISASSEMBLY Part 3
I will now go over how to disassemble rest of the parts that are still on the head (Valve stem seals, valve spring seats, valves).
If your head is still on the motor, you cant take the vales off. So you can use a plier like this but I highly recommend taking the seals off using a special valve seal remover. With the valve still in, its very difficult.
Push the valves out for easy removal. Here they are. All eight valves on the exh side.
Take a plier and grab on it. Now twist and pull. You need to keep twisting as you pull because these suckers are on there tight. This is why with the valves in there, you need a special plier that removes valve seals.
Its like pulling a damn tooth out.
All eight of these farkers taken out.
Head as it sits now…
Now you do not need to do this if you are just replacing seals or valve springs with the head still on the block but if you are taking this head for a machine work (like I am) or going to get it hot tanked (like I am) then you need to take the valve spring seats out. Use a magnetic wand for this as well.
It will come out like this.
All eight of them out. Keep them in order if possible.
How I keep everything together for storage
In the box, in order.
Finished taking all the stuff out of the head. Ready for the machine shop to hot tank and deck.
Side Note: Bleeding Lifters
First of all, this is only for those of you that are still staying with HLAs. I obviously do not need to do this (also those going solid lifters) but for the majority of you…. here is what to do if your HLA looks like this. See the movie below.
You need a container that will hold this amount of oil. The lifter needs to be completely submerged into oil. You also need something skinny to poke through the hole on the top. I chose one of the allen wrenches that I had. It is long enough and provides a nice L so I can grab on to it easier.
Submerge the lifter into the container filled with oil and keep the lifter upright. Now you see why it’s nice to have a container thats narrow because it keeps the lifters upright.
Now using the allen wrench, “jerk it off” like shown in the video. Do this many many times until you see absolutely no bubbles coming out of the lifter.
Take it out and KEEP IT UPRIGHT! You shouldn’t be able to push on it anymore. I suggest you install it on your head immediately to prevent any air from going into it again.
INSTALLATION Part 1
I will go over how to install valve stem seals.
What the head looks like after a trip to the machine shop.
I love engine parts that look so clean…. aaaa this is teh sex.
Total cost at the machine shop $45. Totally worth every little penny.
Some carbon material that needs to be scraped off but ports are nice and clean.
Valve stem seals. As I mentioned before, Intake is from a Sentra SR20 and exhaust side is from any DOHC KA.
Find a socket that will fit over the valve stem seal like shown. I found 11mm to work the best.
Also get a grease can like this one to help you aide in oiling everything. Its certainly not required but nice to have.
Start with oiling the part of the cylinder head that the seal will go on.
Now oil the inside of the seal and the edges.
Put it loosely like shown and try to get it to seat as straight as possible.
Now using the socket and extension, you can either tap it with a rubber mallet or push it with your hand. When using a hammer, do that until you feel a thud and the seal will not go on anymore. When you push, you will feel the seal stop moving.
And you are done with one seal. Now you have 15 more to do….
All valve seals done
Installation Part 2
I will go over how to install valve springs. Before we start, I apologize for taking the pics before getting the head cleaned.
Just for a reference, how keepers go on the valve.
NOTE:Before anything, make sure all your valve spring seats are installed.
Ok now for the steps… First put the keepers in the retainer as shown
Put it over the spring that you want to install.
So its sitting on the spring waiting for you to compress it
Silver tool sucks for this job. Basically you put the black end on, and compress it using your own force… which does not work very well especially with aftermarket springs which are HARD to compress.
Using that tool, you will end up with something retarded like this… Ugh
Now lets use the snap-on tool. MY RECOMMENDATION
Place the tool over the retainer/spring that you want to install
Compress the tool and the keepers will want to come loose like this
Use your fingers like this through the side and try to keep those keepers on the valve stem.
Now the spring is compressed enough so that I can use my finger to place those keepers on the stem either ON the groove or past the groove.
Let go of the tool and voila!
Now let’s do that with Brian Crower Retainers and Springs.
I found that putting assy lube on the stem of the valve like shown helps the keepers stick on the stem much better for easier installation.
Once again, put the keepers in the retainer like shown.
Put it on the valve you want to install it on.
Once agian, you need to use your fingers as you compress the tool
Like shown, compress the springs far enough so that you can use your fingers to place the keepers on the valve.
Let go of your tool and voila! There is your BC retainer and spring.
All of them in with solid lifters.
This looks so sweet. Solid unit… no more collapsed HLAs for me.
Close up of Valve springs/retainers and solid lifters.
Installation Part 3
I will go over how to shim solid lifters properly. Ignore this section if you are going with HLAs as they use different method of shimming.
English version of the Tomei Solid Lifters Manual
Please read this as well. Translated by yours truely.
Tomei Manual pdf
You need to get your rocker arm cut like shown as recommended by Tomei. The following is actually copied from Tomei’s manual. I think this is necessary because the solid lifter is higher than your normal HLA so when the cam lobe pushes on the rocker arm, the tip might dig into the shim. Also more chance of this happening with high lift cams.
I took mine to the machine shop and they did a fairly nice job.
Tomei sells test kits that have 2.7mm and 2.8mm sizes. According to their manual, you use 2.7mm on the exh side and 2.8mm on the intake side. You can see that the ones marked 2700 are 2.7mm and 2800 are 2.8mm. So when you measure cam clearance in intake side, use 2.8mm and use 2.7mm for the exhaust side.
Now. In order for you to measure the cam clearance, you need to have the cam lobe pointing upwards. Since the orientation of the cam lobes on the camshaft doesnt allow you to have all cam lobes facing up, you need to do one rocker arm by one rocker arm. If your head is still on the block, you can rotate the engine to get the cam lobe you want to point up. I obviously can’t do that with the head out of the car so I need to do one rocker arm by one rocker arm.
Install the proper size guide/shim for the side you are working on. The guides goes on the left valve and the shims go on the right valve of each cylinder. Position the rocker arm you want as shown and apply assy lube to cam journals.
Now position the cam in the journals and apply more assy lube as shown
Now install cam caps IN ORDER and tighten to spec. Notice I used the cam oiler temporarily so I can tighten that bolt. Also please stop right here and right now if you do not have a torque wrench to tighten this. You WILL break the bolt and you WILL strip threads. Please go get yourself a torque wrench that can do inch*lb so that you can go in very small values.
You might want to use a good moly lube like this one on the bolts since you will be tightening and loosening alot. Applying this type of lube will be more gentle on the threads.
Now make sure the cam lobe that you want to measure is pointing up and use a feeler gauge to measure the clearance. You need to measure both sides of the rocker pad since the guide side and the shim side might not be perfectly flat.
Here is a picture that Tomei had on their manual telling you to measure both sides.
For those of you who do not know how to use a feeler gauge. You shouldn’t be doing this but I will explain. You want to insert a feeler gauge and feel that the gauge has a slight drag to it. Start by a relatively big size and work your way down until you feel absolutely no drag. Then go up to the next size and you will probably feel a slight drag. Then go up another size and the gauge probably will not go in. You want to select the size that you felt a slight drag.
You can also combine .0015 size and other .00X sizes to go in .0005″ increments as shown. You want to first figure out a ballpark clearance with .00X sizes then “fine tune” with .0015 gauge. For example, the picture shows .0075″. I would use this after I narrow down my clearance to be around .007″
Make a sheet like this and record all the clearance you measure
When you are done it should look like this. (Im still waiting for the rocker arm to come in so my 3rd bank in the exh side is missing info)
Now to figure out what shim/rocker size you need.
1) According to Nissan, they recommend .14~.17mm of clearance between the rocker pad and the cam lobe. You can go with .155mm which is smack in the middle. I chose .13mm because since I have new cams, things will break in and wear out. I wanted it to stay within the limit even after the initial break in.
2) Take the clearance you measured and subtract .155mm (desired clearance: my case .13mm) from it.
3) Multiply that difference by 1.43 (this is the rocker ratio in Tomei manual)
4) Add on the result you got from 3 to the test shim size. And that is the size you need.
Now if this math sounds complicated, download this spreadsheet that I made which will do the calculation for you.
Here is what my spreadsheet looks like with all my clearance entered in.
Visit this site to order proper shims from Tomei.
Side Note: Tomei Shims/Guides
After figuring out what size I needed these are the guides/shims that I ordered from Tomei. One shim was a Nissan size.
Just so you guys know… test shims/guides are identical to the shims/guides you order from Tomei after you figure out what size you need. So if you measure your clearance and its OK with the test shims/guides you use then you dont need to order that one since the test shim/guide will be the same.
All guides/shims I will be using. One guide size I needed was 3mm so I just used a stock one since they are all 3mm. Oh and one more thing. All my clearances are .005~.0055″ (one was .006″) The reason why I decided to run a little tighter is because cams are new and things will break in and wear out. So when they do, they will still be within spec.
I will not go over in detail how to swap your head as that alone deserves another thread but here are some pics and info regarding verifying your valve timing.
Ok now I will go over on how to set-up your cams properly.
1) Make sure your pulley is at TDC (2nd mark from the left) and the #1 lobes are facing outwards as you can see above.
2) Match up that little dimple on the cam pulley to the dark colored chain. Make sure your old cams look like this before you pull them out, that way when you install your new ones, it will go in the same way.. They will not line up like this your first try, just keep turning the crank until they do. I had to turn mine at least 50 times until they finally lined up.
Also count your cam pulley teeth as shown to make sure you are DEAD on.
What they look like.
Also notice from this picture, the keyway on the intake is about 10 O’Clock and the exhaust side in 12 O’clock.
By: Taesoo Kim (ILikeMy240sx)