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Exintake write up.

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  • Exintake write up.

    I'm doing a writeup for this on roadsterdrift too, but I wanted to add to this forum's useful content. Alright, so you want to be that guy all the women want? Thats right, I'm talking about replacing your intake camshaft with another exhaust one. The benefits to this are:

    -more lift and duration on the intake side, which means more beefy midrange power, and perhaps a nice addition to max horsepower, we'll have to see about that on the dyno day though.
    -women sense the lack of pansy-*** intake camshafts in your engine and will ask you about it and want to bang you.

    alright, here's what you'll need:
    -exhaust camshaft that's compatible with your engine (90-93's can't do this mod, sorry. 94-97 1.8L's can only use 94-97 exhaust cams, likewise with 99-00. I don't think this mod is worth it or possible on an 01+)
    -some kind of metal tablesaw, or a trip to a machine shop.
    -assembly lube
    -torque wrench
    -ratchet set
    -to know how to change a timing belt

    ok, so luckily I have this example 1997 head lying around. dorm room mechanic work ftw.

    here are the cams from it, exhaust on the right.

    you can sort of see from this blurry pic how the exhaust cam's lobes are taller (more lift) and the points on the lobes aren't quite as pointy (more duration.)

    Alright, so whatever, let's just slam the exhaust cam into the intake side and get this ***** over with! Well, hold on a sec...

    there's a clerance issue on the intake side because the exhaust cam is longer than the intake one. It has a little ****wad thing on the end of it so it can output to the CAS.

    so, when you put it in place, you end up with a clerance issue like so:

    the next step is to cut that part off of the cam. I'm taking my cam to a machine shop to get it cut totally level, as to not throw off the balance of the cam. I doubt it matters that much though, i know a guy who did this mod with a hacksaw, lol. Either way, I'll update this as soon as I get it cut, then I'll show you how to get it timed correctly!
    sigpic

  • #2
    Nice write up mate! Probably the clearest one I've seen so far on this subject.

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    • #3
      Originally posted by N3v View Post
      dorm room mechanic work ftw.
      nice
      MS2, VVT, 650cc, Spec S3, MMR, 6 speed, 4.30, AEM , ARP, ... one day ill get a real turbo

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      • #4
        I wonder if the 99-00 exhaust cam is lacking the extra mass since there is no rear CAS. But then again, there is a way to mount the rear mount CAS to a 99-00 with a little bit of wiring....so it might have it.

        And for clarification, this cannot because of the VVT.

        I'm curious to see how much more power this will add. goodluck!

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        • #5
          Good write up, have ordered the cam and plan to do this soon
          Kinda inherited the car from my Grandfather. Its a love hate relationship. lol

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          • #6
            Originally posted by Doppelgänger View Post
            I wonder if the 99-00 exhaust cam is lacking the extra mass since there is no rear CAS. But then again, there is a way to mount the rear mount CAS to a 99-00 with a little bit of wiring....so it might have it.

            And for clarification, this cannot because of the VVT.

            I'm curious to see how much more power this will add. goodluck!
            the 99-00 cams also have that rear piece

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            • #7
              Originally posted by redrumracer View Post
              the 99-00 cams also have that rear piece
              yeah the 99-00 cams are similarly setup, they have a more aggressive exhaust cam as well. The only real difference that's relevant to this mod is that the 99-00 head uses solid lifters. So you cant use 99-00 cams if you have a 94-97 head unless you also switch to solid lifters. That's also doable, but a little tougher though cause you have to reset your valve lash.

              on a 94-97 you can actually get a gain just from swapping to solid lifters and 99-00 cams, and even more if you switch to two 99-00 exhaust cams. I think at that point though you should probably just get a set of aftermarket cams.
              sigpic

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              • #8
                Originally posted by N3v View Post
                yeah the 99-00 cams are similarly setup, they have a more aggressive exhaust cam as well. The only real difference that's relevant to this mod is that the 99-00 head uses solid lifters. So you cant use 99-00 cams if you have a 94-97 head unless you also switch to solid lifters. That's also doable, but a little tougher though cause you have to reset your valve lash.

                on a 94-97 you can actually get a gain just from swapping to solid lifters and 99-00 cams, and even more if you switch to two 99-00 exhaust cams. I think at that point though you should probably just get a set of aftermarket cams.
                and just imagine if you swap a whole 99-00 head :D

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                • #9
                  alright, it's done, and the results are glorious. again, probably accentuated because of the itbs, but anyway, here's how you do it. unfortunately I don't have any pictures of this part because I was too busy busting my knuckles, but its pretty straightforward. Keep in mind, I kinda did this a dirty way, and only because I'm gonna replace my timing belt pretty soon anyway.

                  step1: remove valve cover and front cover
                  step2: pull the timing belt off of the cam gears with your fingers. it's doable.
                  step3: remove intake cam, which involves unbolting all of the cam caps. Even after unbolting the cam caps its still pretty stuck in there. I found the easiest thing to do is to rotate the cam with a ratchet, the valve springs push against it and undo the lock that the cam caps have formed. after that I was able to just pull it out. make sure you pull straight though, you don't want to mess up the cam journals.
                  step 4: put the exhaust cam into the intake side. Now, here's where someone who wasn't a dirty ******* would probably use assembly lube, but instead I just covered the exhaust cam in motor oil and rubbed it into the journals and lobes. I did that because my head and the cam are already broken in. It runs fine. Anyway, put it in and tighten down the cam caps with a torque wrench.
                  step 5: install a new cam seal on the new intake cam, then install the stock intake cam gear. the key on the cam should go into the I marked slot on the cam gear.
                  step 6: timing. set the exhaust cam up like normal when doing a timing belt, set the I to the I notch on the engine block. The intake cam, however, count 25 teeth counterclockwise from the E notch, and mark that tooth. Line that tooth up with the E notch on the intake side.

                  step 7: put the timing belt back on. here's the fun part. I'm not even going to go into detail on the quick and dirty way I put the timing belt back on, but it involves just setting the crank to tdc, aligning the gears, and man handling it back on. That said, if you're the kind of person that believes you shouldn't re-use a timing belt once it's been de-tensioned, I recommend doing this mod while you do a timing belt swap.

                  it took me two tries to get the timing set right with this method, but once I did it started right up.

                  effects: first thing i noticed, my exhaust is more burbly, which sounds sexy. it seems to rev a little more smoothly. on high rev decel it pops fire more often. as for the power, it really hits around 3600 and as far as I can tell stays until the redline. the itbs sound a little different on WOT, they shound meaner and sharper, I'm guessing because of the added duration. The extra meety midrange really kicks *** for highway driving when you part throttle from 60-70, it does it much faster.

                  As for overall added whp, the butt dyno says 15hp. I'm thinking my stock exhaust system is very restrictive to the itb power, and even more to the extra cam, so I'm expecting another 15-20hp from a full exhaust. i've heard itb's respond very well to more intake cammage, so you can expect more like 8-12hp if you already have an exhaust. People on mnet got 125 wheel with a stock car with a catback and this mod.
                  Last edited by N3v; 02-13-2009, 03:49 PM.
                  sigpic

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                  • #10
                    awesome write up!!! mine will be done next monday!
                    Kinda inherited the car from my Grandfather. Its a love hate relationship. lol

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                    • #11
                      thanks! oh sorry I also forgot to post this. when you cut the cam it will end up looking like this. exhaust cam on the left.

                      even though its a little longer it still totally clears the head
                      sigpic

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                      • #12
                        Excellent write-up. Now I need to find a 99 exhaust cam to try this with.

                        I really can't wait to see your dyno results.

                        My only question is this: Is there now too much overlap for boost? (I realize you probably won't be boosting your already ITB'd car, but some of us plan to boost ours).
                        1991 UK-spec MX-5 - https://www.facebook.com/djinovaband <<< METAL!

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                        • #13
                          Best cam is the MSM intake cam. It's the same cam from JDM 99+ Miatas and requires no machining. Drawback is higher initial cost, but you do get a new cam instead of a used one.

                          exhaust-intake is the 2nd best, harder to do, but cheaper. a used cam from application 1 installed with used lifers from application 2 is far from ideal, but people so far do not seem to be reporting problems.

                          99+ exhaust cam absolutely has the flange to drive a mechanical CAS.

                          01+ this swap is not possible.

                          For boost, I'd rather do adjustable cam gears than this. The MSM cam doesn't make good power over 6K boosted.
                          DIYAutoTune.com

                          | 10AE-T | BEGi S4 | GT2560r | Enthuza | 6UL | MS3Pro PNP|
                          | 2001 Track Rat | Enthuza | Jenvey | MS3Pro PNP | Exocet in Progress|
                          | 1992 323 | Wrong-wheel-drive Miata Endurance Racecar|

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                          • #14
                            http://www.youtube.com/watch?v=_kY7wsy7crQ
                            sigpic

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                            • #15
                              Nice bass BTW, Ibanez Soundgear?

                              and [email protected] quad turbo
                              1991 UK-spec MX-5 - https://www.facebook.com/djinovaband <<< METAL!

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