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Evo 8 Camshaft Install

It takes air (and fuel) to make power and one of the best ways to get more air through the engine is to add performance camshafts with higher lifts, longer durations, and more overlap. These will open the valve higher and/or for a longer periods, thus allowing air to flow more freely. A decent set of cams could easily add 20-30 HP to your Evo.

Although, fairly in-depth, this install write up is intended as a general process, not a step-by-step Installing Evo Cams for Dummies (though it's close :). Installing camshafts is not for the newbie unless you are absolutely sure of your ability to pull this off. Failure to install cams properly or correctly check and set timing can totally destroy your engine.

We will be using the Mitsubishi "Timing Belt Tool" for this install. If you do not own this item, you will have the additional labor of removing and replacing the timing belt, which adds greatly to the total install time as you might imagine. The removal and replacement of the timing belt will be shown in a separate section at a later date. If you do not have the timing belt tool, you should really consider getting one (click here to purchase evo timing belt tool).This toolwill save you hours of work whenever you need to remove the cams or the head.

1. Start off by raising the front of the car and supporting it on jack stands or ramps.
2. Remove the bolts holding the throttle cable, main wire harness, and spark plug cover to the valve cover. Remove the vacuum hose from the metal tube at the back/right of the valve cover. NOTE:The order of these initial removal steps is almost a moot point...everything attached to the valve cover must be removed so the valve cover can be pulled off. The individual steps are only included here for the sake of completeness.
3. TECH TIP: A good way to not loose any of the numerous bolts that hold things to the valve cover and to make sure the correct bolt goes back where it came from, is to replace the bolt in the valve cover after you remove whatever it was holding.
4. Remove the four 10mm bolts on cam gear cover. Note that the lower bolts are longer than the top. TECH TIP: the easiest way to reach the rear/lower bolt is with an open-end wrench from the back.
5. You may need to remove the 12mm bolt holding the power steering hose to the top of the motor mount to get the cam gear cover out.
6. Disconnect all sensor harnesses that run over the top of the valve cover (cam angle sensor, O2 sensor, coil pack harness, and EGT harness if installed). To remove the cam angle sensor harness from its bracket, simply pull it straight up off of its base (left inset). Remove the two 10mm bolts holding the O2 sensor harness to the top of the valve cover (right inset).
7. Remove the harness to the coil pack on cylinder #4 and then remove the coil packs (held by three 10mm bolts each) and the spark plug wires.
8. We now need to remove the hard line that connects the intake reference to the BOV. First disconnect the rubber vacuum hose at the BOV. Remove the 10mm bolt on top of the cam angle sensor (remove the vacuum hose to the valve cover to reach it). To remove the 10mm bolt under the wire harness, remove the harness from its bracket by pulling the tab forward and lifting straight up, as shown in the inset.
9. If everything went according to plan, you should now have a barren valve cover!
10. Disconnect the cam angle sensor and the 10mm bolt holding the ground to the cam angle sensor housing. NOTE: The entire cam angle sensor housing will be removed with the exhaust cam.
11. Under the passenger side wheel well, you will want to remove the inner splashguard to access the crank pulley and accessory belt tensioner. You can simply remove the round plug to access the crank sprocket bolt to simply rotate the crank, but it's much easier to read the timing chart if you move the accessory belt from the water pump pulley, so we need access to the tensioner. If you are doing the install without the timing belt tool, you will need to remove this anyway.
12. To make the crank timing mark and timing chart easier to read, and at a better angle, loosen the accessory belt tensioner and pull the belt off of the water pump pulley (directly above the crank pulley). To the left of the crank pulley is the accessory belt tensioner. Before doing anything, find an allen key, drill bit or other similar object that closely fits the hole size, as shown.
13. Grab that 1/2" drive or breaker bar that you will use to rotate the crank and insert it into the square opening in the tensioner as shown. Pull counter-clockwise to release the tension on the belt.
14. When the two holes align, push the allen key, drill bit, etc. through to hold the tensioner open. Once the tension is released from the belt, push the serpentine belt off of the water pump pulley towards the fender (ie. away from the timing belt cover), then get up top and look for your timing chart and crank timing mark.
15. Ah, much easier to read! Yes, that's right, when the cams are set on time, our crank mark is a degree or so BTDC, not exactly on "T". Likewise, if the crank is set at TDC, the cams are little advanced. Don't freak, it's not uncommon to see this on 4G63s. What causes this? We don't have a definitive answer for you, but when dealing with rubber timing belts and hydraulic tensioners, there is plenty of room for "play". There is also clearance between the crank pulley key and keyway, maybe the "eyeballed" TDC alignment isn't dead on, etc. So was our eyeballed TDC off? No, because we didn't eyeball it. We used a degree wheel and positive piston stop to find true TDC. The crank mark was 1-2 BTDC, the intake cam looked dead on its mark and the exhaust cam actually looked a little (very little) advanced on its mark. Suffice it to say that however much your marks are "off" when stock, if at all, is simply the way it is. Why? Experience with 4G63s in DSMs tells us this, but something you will find easier to swallow is that unless you've already messed with the timing belt, it's definitely, without a doubt, 100%, dead-on time from the factory, regardless if a pulley's tic doesn't perfectly line up with its TDC mark. Note that we keep saying when "timing marks when stock". After you do anything with the timing belt, there is always the possibility that you messed something up. We've never been concerned about 1-3, but if timing is ever more than 4-5 off after you mess with it, it's much more likely that you have a pulley one tooth off. In any event, line up TDC as close as you can. If anything is "off" just make note of it...that will be your target when you are done installing the cams.
16. Now grab that 1/2" drive again and with a 3" extension, plug it directly in the middle the crank sprocket bolt to rotate the crank. TECH TIP: The longer the ratchet/breaker bar you use, the easier it will be to rotate the crank. TECH TIP: Though you will not "need" to remove the spark plugs for this install, if your engine position is far away from being at TDC, loosening (or completely removing) the plugs will let out any compression that builds up, making it easier to rotate the crank. Since the crank timing will "vary" (usually ends up a few degrees BTDC), line up TDC on the cam pulleys. Rotate the engine clockwise so that both cam pulleys' timing marks line up with the timing marks on the valve cover. When they are set, make a note of your crank pulley timing mark. TECH TIP: If you don't have a 2nd set of eyeballs at the top of the engine to watch the cam or crank timing marks, you are close to TDC when the crank pulley key (dowel pin) is just about perfectly pointing to the front of the car. Note that the dowel pins on the cam gears will be a few degrees before and after straight up on the intake and exhaust cams respectively when at TDC. When the cam pulleys are lined up, the crank pulley will most likely be a few degrees BTDC.
17. Alright, now that we've confirmed the crank and cam pulleys are at TDC, we can remove the valve cover so we have access to the cam gears... Remove the twelve 10mm bolts holding the valve cover down. Carefully pull the cover off. The gasket maybe to stuck to the head with sealant in the corners of the outside cam bearing caps and may be pulled out of the cover. There are four individual gaskets around each spark plug holes, make sure not to lose any. It is a good idea to stick the valve cover in a clean plastic trash bag and set it in a safe place...don't leave it open and laying on the floor and never set it down on the gasket side to keep it clean. NOTE: once the valve cover is off, be extremely careful about not dropping or getting anything inside the head. Keep the shop/garage as clean as possible while the cover is off. Even the smallest piece of trash can clog some oil jets and/or score journals/bearings. If you have to stop in the middle of the install for any reason, lay the valve cover or a clean plastic trash bag over the head to keep junk out.
18. We want to break the cam gear bolts loose prior to inserting the tensioner tool. This is done in case there is any movement of the timing belt that may throw the timing off of TDC while trying to break the bolts. Hold the cams at the nut section (outlined) with a 26mm or 1-1/16" open end wrench. If you don't have an open end wrench that large on tap, an adjustable wrench (gulp) will work too. Most aftermarket cams will either have the same 26mm or a 25mm (1") nut on them. If you don't have an impact gun, getting the cam gear bolts off is all about leverage. Just make sure not to punch a nice big dent in your aluminum hood when those suckers finally break loose. Do not remove the cam gear bolts, just break them loose. And, yes, the stock cams are definitely hollow as can be seen by the hole in the middle of the nut.
19. Re-check your timing marks to see that they are still on TDC. Simply lay the valve cover back on the head to verify the cam timing and check that the crank mark is in the same time as you noted in Step 15. If the timing is off, move it back to TDC. When you are sure everything is at TDC, grab some tie straps and strap the timing belt to the cam gears.
20. Get your timing belt tool (inset) and insert it into the access hole at the front of the timing cover. Thread it in by hand and then slowly tighten it down with a socket. Waiting a few seconds between turns will allow the auto tensioner to settle and will make turning it easier.
21. With the tensioner compressed, you can see the slack added to the timing belt. If the timing belt wasn't strapped to the cams at this point, you would be doing a complete R&R of the timing belt to fix your timing.
22. With the slack in the timing belt, you may now finish removing the cam gear bolts and pull the gears off of the cams. TECH TIP: Have some tie straps handy to tie up the timing belt and gears to the A/C line when you pull them off. Pull off one gear at a time and keep some tension on the timing belt. The timing belt can fall off the crank sprocket while there is slack in the belt, so take the precautionary measure of taking up as much slack in the timing belt as possible by tying them up.
23. One extra step to removing the exhaust cam is to unbolt the cam angle sensor trigger from the cam and/or the cam angle sensor housing from the head to remove the shebang with the cam. The cam angle trigger is bolted to the cam inside the housing and the cam will not come out unless either the housing is detached from the head or the trigger is unbolted from the cam. We prefer to remove the entire housing. Since the factory seal will be broken with the removal of the #6 cam bearing cap, you will want to remove the housing and replace the entire bead with fresh sealant anyway... Why do we do this now? Once the cam bearing caps are loosened, the valve springs will push the entire cam up and the cam angle trigger along with it. We don't want to mash the trigger into the housing, so either remove the trigger or unbolt the housing now so everything is free to come out with the cam. TECH TIP: To make things easier for after the cam and CAS housing/trigger are removed from the head, you may want to break the CAS trigger bolt loose while the cam is still in the head. Use a wrench to hold the cam while you break the CAS trigger bolt. You won't have much leverage on the cam after it's out of head, so doing this now will save you time later. If you do not have a universal joint for your ratchet (or a mid-length 12mm socket), you are going to have a difficult time reaching the trigger bolt while the cam is in the head, due to the radiator hose/waterneck (top pic).
24. To remove the housing, you will need to remove the 12mm bolt on the bottom of the housing (bottom pic, left - bolt hiding in the shadows, not the sensor retaining bolt facing forward) and the ground from the side of the housing if you haven't already. Also remove the 12mm bolt on the top/back side of the housing holding it to the head (bottom pic, right). The housing itself has sealant between it and the head, so break that seal loose before trying to pull the cam out with housing.
25. Before we get to removing the cam bearing caps, there are a few things you should take note of about them. The caps are well marked as to which journal they go to and which way they face. The caps are bored and honed on the head and are therefore a perfect match only for the head and the journal they come off of. They are not interchangeable with other cam bearing caps, even on the same head. The caps must always go back on the location they came from and in the same orientation. There's no way to mistake the #1 or #6 caps with the others, but we've noted the cap markings and what they mean for clarity in the picture (no making fun of our pretty "shop towels" :). TECH TIP: To avoid any confusion, it's always best to R&R one cam at a time and place the bearing caps in a clean, safe place in the order and direction they come out.
26. Now it's time to remove the cam bearing caps. Like head bolts, these need to be loosened in stages, beginning on the outside caps and criss-crossing your way to the middle. Repeat the criss-cross pattern doing a few turns at a time on each bolt until they are all loose. Once loose, we usually leave the bolts in the caps and use them to "rock" the caps off. The bolts should be pulled up so the end is about 3/8" from the top of the cap for this. There are sleeves inside protruding up out of the head and if the bolts are too low (still in the sleeve), you will obviously not get the cap off and will probably just bend or score the sleeve. Some caps may need more "persuasion" to come off and you can use your imagination for those. Just do not scrape or score anything and definitely do not get anything in the head while you are working. Always make sure that any tools you are using to work in or over the open head are completely free of dust, dirt, metal shavings, etc. TECH TIP: On occasion for truly stubborn bearing caps, we have found it necessary to lay a breaker bar across the head (for a fulcrum point) and gently push the entire cam up with a crow bar to get the bearing caps moving. There are some caveats to this however: only contact the rough casting areas of the cams (not on the lobes, duh), don't be foolish with how hard you push...you can hurt the cam, and only do this just enough to get the stubborn cap(s) barely off the head, then work them off by hand. If one side of a bearing cap gets too high while "walking" it off, the angle will cause it to get stuck on the inner sleeves. If this happens, don't hit the cap directly. Remove the bolt from the high side, place a 10-12mm socket with an extension over the empty bolt hole and gently tap the extension to level the cap back out, then continue walking it off. NOTE that the #1 caps (nearest the gears) may not come off no matter how much you try. They can come off with the cams (lift straight up) and be pushed off afterward. The oil seals (and some sealant) sometimes really don't want to let them go and make it very difficult to remove them with the cams in the head.
27. Remove the cam CAREFULLY. With the cam removed, the rockers are doing little more than balancing on the valves and lifters. There are plenty of nooks and crannies in the head for those guys to get lost/stuck in, so be careful that none fall off.
28. Remove the 12mm bolt holding the CAS trigger to the exhaust cam. If you broke this loose with the cam in the car as suggested, this will be a snap. NOTE the orientation of the trigger vanes on your cam before you remove the trigger. The larger vane should be to the RIGHT side of the dowel pin (on the cam gear side) when looking at the cam angle sensor side of the cam. It will be the first fully seated position in the slit to the right of the dowel and should face down/right at about a 45 angle when the dowel pin is straight up. The trigger will need to be reinstalled in the new cam in this same orientation.
29. With the trigger out, remove the housing from the cam. You will need to clean off any leftover sealant from the channel around the opening on the backside of the housing, as well as on the head where the CAS housing was. Fill the channel on the back of the housing with sealant after it is cleaned out and leave enough over the top to contact the head and make the seal with the #6 cam bearing cap.
30. Get out your assembly lube and apply it to the cam journals and lobes. You will want to insure that the entire surfaces of the journals are covered all the way around. TECH TIP: Prior to installing the cam back in the head, clean out any oil in and around the #1 and #6 bearings so it does not interfere with sealant adhering to the head. TECH TIP: Lay the cam in the head with the dowel as close to TDC as you can. Since the valve springs are all fully expanded, it will be impossible to get it anywhere near TDC, but just make sure that it isn't facing down. Gently rotate the cam until it sits down as far as it will go in the bearings and be careful not to lose any rockers while doing this! Remove the oil seal from the stock cam, lube the inside ring that the cam rides on with clean engine oil and install it on the new cam. The seal should be pressed flat against the head, with a dab of sealant in the back/outside corners where it meets the head on each side of the seal.
31. After the lubed cam and oil seal are installed in the head, replace the cam bearing caps in their correct order and orientation. Similar to the method used to remove the caps, we need to go in a criss-cross pattern, but this time, start in the middle and work your way out. This will take several passes, doing just a few turns each time until all of the bearing caps are seated fully against the head. TECH TIP: You should install the CAS housing on the side of the head while the #6 bearing cap is still slightly off of the head. You want to leave enough clearance for the housing to fit into the journal, but you do not want to scrape off the sealant with a lot of downward motion on the cap as it is tightened down. When the bearing caps are all seated, break out your torque wrench and torque in the same order (middle, criss-cross out) to 14-15 ft-lbs. Depending where you look up the spec, it's 14 ft-lbs +/- .5 ft-lbs or 15ft-lbs +/- 1 ft-lb. Both are listed in the service manual. We split the difference and used 14.5 ft-lbs on our install. It would be ideal to first back off a half turn to make sure you didn't accidentally over tighten during the initial process, then torque to final spec.
32. With the CAS housing installed and the cam bearing caps torqued down, reinstall the CAS trigger. Remember, the larger trigger vane will be in the first fully seated (in the slit) position to the right of the dowel pin when looking at the cam angle sensor side. Torque the trigger bolt to 16 ft-lbs while holding the cam with a wrench. When installed properly and with everything in time (we're not at there yet in this install), the larger trigger vane should point down/right at about a 45 angle as shown in the picture. You may wish to leave the CAS cover off until the cam install is completed to verify its position when everything is set in time, as we have done for this picture.
33. OK, the most difficult cam is done! Repeat the R&R steps on the intake cam, but skip the cam angle sensor stuff :) When you are all done with that, you should have two new cams in your head and your stock cams safely stashed in the packaging that the new cams came in (make sure the old cams still have oil on them in the bags for storage).
34. You will need to reposition the cams to line them up with the dowel pin holes in the gears. Like we did when removing the cam gear bolts, use an open end wrench on the nut part of the cam to move it back towards its TDC position. Press the cam gear on and hand tighten the bolt. Repeat for the other cam. While still holding the cam with the wrench, torque the cam gear bolts to 65 ft-lbs. NOTE: While reinstalling the cam gears, do not let the gears fall, and be careful not to turn the timing belt...turn the cams to meet the gears, not the gears to meet the cams. Remember, the timing belt is basically flapping in the breeze over the crank sprocket and any movement can cause it to slip into the next tooth.
35. If things go well, when the car gears are reinstalled, you should again have the same slack between the gears, just like you did when you first installed the tensioner back in Step 21. The cams should be on, or very close to, their in-time positions.
36. Remove the timing belt tensioner tool, cut the tie straps on the cam pulleys and then rotate the crank 2 full turns clockwise. The slack should be gone from the timing belt and the everything should be in TDC positions. Lay the valve cover in position to verify the cam timing and if everything looks good there, check the timing mark on the crank pulley. If the crank timing mark is in the same position as you noted in Step 15 as well, you have successfully installed your cams! If a pulley is not in time, all we can say is it sucks to be you! :) Your quickest course of action would be to set the crank at its original time (Step 15), use the timing belt tool to loosen the timing belt again and then adjust cams gears as necessary. If only one cam gear is off time, tie strap that gear to the timing belt so it stays put and concentrate on the one that's off.
37. Never, ever run the car unless you have rotated the engine and checked that the crank and cams are all in time at least twice. This also helps the assembly lube completely coat the bearing with slow revolutions before starting the car with the new cams.
38. Once you're absolutely sure that everything is in time, pull the valve cover off. Remove any old sealant and degrease the areas where fresh sealant needs to be applied. Where exactly is that? Apply sealant to the 6 corners where the valve cover meets the #1 cam bearing caps and the cam angle sensor housing. Also, put a small bead across the top of the end seal (next to #6 bearing of the intake cam). Mitsu calls for a very thin bead of sealant across the front and back of the head where the valve cover gasket sits, but uh, we've never done it and this install was no different. It's your call.
39. Once the sealant is applied, carefully install the valve cover and insert the bolts. Like the cams, it's advisable to begin tightening the inner bolts first and work your way outside doing a few turns at a time until they're all hand tight. Torque the valve cover bolts to 31 in-lbs. The torque specs for these bolts is so low, it is definitely recommended that you back off a half to one full turn first, then torque to spec. TECH TIP: It's important not to over-tighten the valve cover bolts. They are extremely low torque bolts, so pay attention to that fact. DSM valve covers are notorious for cracking due to over-tightened bolts, although they are not Magnesium :)
40. Now, put the rest of your mess back together! Some of the following torque specs might be useful and some are just there because we came across them :) Make sure to note IN-LBS .vs FT-LBS.
41. Once your car is back together, give it the all-important first start. If everything was in time before you put it all back together, everything should be just fine, assuming you haven't purchased cams that are too big :)
42. TUNING TIP: With more aggressive cams (and more overlap), you will lose vacuum. How much depends on the cams themselves. With our HKS cams, we went from about 17 in/Hg (0.6kg/cm2) at idle with the stock cams to about 14.5 in/Hg (0.5 kg/cm2). With the A/C and other accessories running and on the brakes, this could get as low as 11.5-12 in/Hg (0.40-.0.42kg/cm2). You can see how that could cause a problem with stalling. Since the stock vacuum is on the weak side already, you may find your Evo wanting to stall at idle with aftermarket cams, particularly when driving. Letting off the gas and immediately hitting the brakes is a prime example of the most likely time this will happen (power brake booster uses vacuum to operate). You may want/need to adjust the idle up a hair and possibly add some fuel in with a management system at idle to help "catch" it before it wants to stall when you let off the gas. The quickest way to adjust the idle is to use the idle air by-pass screw on the top/back of the throttle body. It is basically a big Phillips screw (with an o-ring around it) and it controls how much air by-passes the throttle plate at idle. Obviously, the more air allowed into the intake, the higher the idle will be. Counter-clockwise turns increase idle RPM, while clockwise turns decrease it. We bumped our idle up to ~950RPM and added 16% fuel at 800RPM just to give it that extra little bit of help. Obviously, you will need to re-tune the rest of your fuel curve to take full advantage of the new cams.
43. Enjoy your new cams and power! If you have any questions regarding this install, or find something we missed in the write up, please contact us.

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