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Old 02-07-2007, 12:37 AM   #1
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SR How To Replace Camshafts *Approved*

Tips and inside advice on camshaft upgrade for you SR20DET.

This is all off the top of my head, seriously if you see something off or you would like to also contribute as a tip feel free.



First Lets start by reviewing removal and reinstallation of camshafts.

To do this you do not need an FSM if you at least know general Maintenance of the sr20det engine. Warning this is for Cams that do not require valve spring upgrades only, you might cause engien failure if the lift or Duration is too much for stock or warn springs-PS-Any Sentra Manual will supply you with proper losening and tightening sequence for cam caps as well.

Step1:
-Pull the car up into a safe area, if it looks cloudy get cover you don't want any water or excessive particulates in the valvetrain or timing cover/oil
-remove the positive terminal of the battery, just to be safe.
-Get your tools ready. A rachet with the following sockets will suffice
*27mm *24mm, 12mm*, 10mm*,8mm* as well as a large adjustable wrench.

Step2:
-Remove the valve cover (should all be 10mm stop nuts)
-Remove the oil catch hose from the Vlave cover T on the exaust side
as well as the vacum line to the integrated PCV valve on the intake side of the valve cover.
Make sure not to lose any of the washers.
-Also take care to not rip or tear the Valve Cover gasket. If it has been reused before or is the one that came with the swapped motor I highly suggest replacing it.
-Remove the Crank Angle Sensor (once the valve cover is cleared).

Step3.
-Remove the spark Plugs. (this will make turning the crank easier)
-Get your 27mm Socket on a breaker bar or large rachet.
Crank the Engine until the shiney links match up with the dots on the cam sprockets for your engine's camshafts. The Timing Cover Pin/Pointer will also line up with the 2nd notch from the left on the crank pulley itself. See pic.

This is True TDC (you can also double check with a long flat head down cyl no.1 to make sure th piston is at its peak hieght in motion/path in cyl.


-Now take some White Out or White Marking paint and swap it across the link and the corresponding dot area on the sprocket as a double assurance when you go back to re-install the sprockets.

Step4.
-Remove the Timing Chain Tensioner
-Grab a Friend to watch and Hold the Timing Chain tight with his hand and a glove preferably (saftey glasses if your spazmatic) on the exaust side so it does not slip off the corresponding link/dot on the crank shaft. You really dont want the chain skipping a link if your not pulling the head and timing cover. Not Fun in car...trust me.
1. Do this slowly and with patience (if you loosen one of the nuts too much in relation to the other nut the actual body of the plate that blocks off the dowel hole where it slides in can snap and then youll need a new tensioner.
2. Once the tensioner is out you shoudl get a little more slack on the top of the chain between the two camshafts. You will also have noticable slack on the intake side timing chain guide that is attatched to the front of the Block.
Slack on that side (if its minimal is ok) exaust needs to stay tight.
3. Get a piece of metal wire or some strong electrical wire and tie the chain off to something above it like a piece of the car hood or the top of your garage etc. or just keep your Buddy Handy for a little longer.


Step5. Camshaft Removal
1.Get the large adjustable wrench. now there will be a notch on the camshafts themselves where you can grip the cam without them moving.


2. Now get an AIR GUN or AIR Rachet and use the 24mm socket to gently tap some air in the reverse direction to losen the sprockets while holding the cam in the service notch with the adjustable wrench.
3. Take each cam sprocket off, just pull gently they will come off the key.
Make sure your friend or your self hold or ties up the timing chain Again to account for the new slack of no longer being attached to the cam sprockets.
now its time for removal!

4.Get the 10 mm Socket and the wrench and losen the cam shaft caps in this sequence. -Cam cam no.3 is first and the outside bolt is always first. Then Insaide no.3 Then outside no.4 (1-5 from front for engien to back). Then inside no.5 and so on in a staggared losening pattern. Losen them about one full turn each time so to prevent snappage. A better layout of losening sequence is in any SR20DE or GA16/KA24DE manual. So you get the idea of cross losening across the top of the cam.


5.Once all the cam caps are lose remove the cam caps and label them according to placement. This is very important do not mix them up or lose them or get them out of order. I usually wipe of the oil and use white out or permanent blue sharpie to write on them as well as on a index card that goes in a ziplock baggy with each cap and set of bolts.
6. Now pull the cams up and out, check for excessive wear on the cam journals and the head.

Step6.
Installing the Camshafts
-Get your new camsaft and a thick towell, your Air Gun , the 24mm socket, and the adjustable wrench. ALso grab the appropriate sprocket depending on whether it is an intake or exaust cam.
-Set the back of the cam or the butt against the thick folder towell on a work bench or the floor etc. grip the cam by the service notch/nut shaped area.
-Set the sprockets on their keys (little metal pin that sticks out so its retard proof) aka noob proof.
-screw the camshaft bolts all the way in hand tight. Then hit them with the air while you or a friend holds the adj wrench to keep it from moving.
your ready to drop the new ones in!

Step7.Drop and Finish installation.
-Oil the oil galleys and cam journals with a little bit of engine oil.
I always put the Exaust camshaft in first.
Then drop the intake cam shaft make sure they seat as much as possible into the head. Angle the sprocket down and out when you do this so you can slide it in and line up the marks/dots on the chain and cam sprocket again.
-Once this is doen there should still be a little slack in the timing chain because the tensioner is still out.
-Tighten the cam caps in their proper places with the Oil Squirter or RAS etc that you have on your caps. The oder for Tightening is exactly opposite of losening so rear right cap bolt then front right and so on switching off side and orientation.
-Set the Torque Wrench for 8 Ft Lbs In my experience this is plenty that enough. Most of the Bolts stretch over time and servicing and unless you get new ones do not torque to 10-12 ft lbs.
-Once all cam caps are in and the notches are lined up on the cam sprockets etc. put the chain tensioner back into place.
-The engine shoudl still be at TDC if you have done evrything right.
Apply some RTV to the Tensioner Gasket Press it in and tighten it down. Usually its a lot easier to press into the head if the timing chain is lose on the intake side still. If it is not turn the cam just a little bit with your adjustable wrench or the big cam socket until its easier to press on to the studs.
-No the second fun part actually pretty satisfying.
-Take the 27mm (crank pulley socket) and your breaker bar. Turn the crank shaft backwards about 15 degrees or until the timing cover pin/pointer is off the notches completely (rotate counter clockwise if you standing in front of engine).
-The Timing Tensioner arm should shoot out and adjust full tension onto the chain.
Now insert the CAS


Step8 Valve Cover and Clean up
-pretty self explanitory.
-Apply some silicon to the new valve cover gakset journals for the two on the back of the head and the two half moons on the front of the head. Press down and star tighting the valve cover nuts with their washers.
-Make sure after the PCV and Crank vent are back and your Put fresh Oil etc in the car that you re-check the Timing with a timing light.

cheers.

Next installment will be installation of Swirl Tank (bleed pot).
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Old 03-26-2007, 06:11 AM   #2
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