DIY Exhaust Manifold Port and Polish
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This is a discussion on DIY Exhaust Manifold Port and Polish within the Engine Performance forums, part of the Tutorials & DIY category; here is a good writeup about everything you need to know port and polish related: http://www.sa-motorsports.com/diyport.shtm and here is my ...

  1. #1
    Registered User Wrinkleboi's Avatar
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    DIY Exhaust Manifold Port and Polish

    here is a good writeup about everything you need to know port and polish related: http://www.sa-motorsports.com/diyport.shtm

    and here is my interpretation of it applied to my wrx:

    ok so on sunday i had a marathon port and polish in my garage. thanks to wil for coming over for a bit and getting me started... it takes a looooong time to do the wrx exhaust manifold at least, since there are 9 different places that can be done.
    i was very slow and careful on the first one and it took forever. as the day went on i got more comfortable and applied a lot more pressure and just went at it.
    i dont know if my job would win any awards for looks... i wasnt quite as concerned with that as just getting them opened up and matched decently well for whatever performance gains i could achieve.
    anyways, on with the photos...

    complete exhaust manifold, with gaskets


    comparison of ported manifold versus stock untouched. notice the carbon buildup which indicates the difference in size between the actual opening and the gasket. right off the heads you want to just open these up as much as possible, but of course keep them slightly smaller than the gasket so it can seal properly


    stock crosspipe versus ported one. this pipe has a flex section in it and therefore is 'sleeved'. this sleeve creates an abrupt step which you want to grind to a much smoother transition



    port matching requires matching the outlet of one pipe as closely as possible to the inlet of the pipe that bolts up to it. to do this i took a sheet of posterboard on the larger of the two and cut a template of the exact opening size. i laid it onto the smaller one and basically grinded away until it matched the template. yes i know my template is ghetto but i just used it as a rough guide. also notice that i didnt open up the inlet as much as possible... thats the point here, you only want to open it as much as is needed to match the pipe it is being mated to.




    and here are some finished product shots...




    oh and i almost forgot to mention... arguably the biggest benefit to this mod is the mad tite weight savings yo



    and since someone is sure to ask if i can feel a difference...
    unfortunately i only installed the new turbo setup about 5 days prior to pulling my car apart to work on the exhaust manifold. so really, i never got that good of a feel for the car with the turbo upgrade and stock manifold. therefore i really cant tell a difference here becuase i dont have a baseline.
    but most schools of thought agree that this type of work will result in slightly earlier spoolup and a few horsepower or so. nothing too crazy but slight benefits that require a good amount of time but absolutely no money (assuming you have the proper tools already)
    bryan

    -2003 Blue WRX, complete 2007 STi Engine/Drivetrain transplant - Pic 1 | Pic 2 | Pic 3 | Pic 4 (new!)
    -1994 Black Supra TT 6MT - Pic | Build/Restoration Thread: 67mm, Fuel, Painted Engine Bay, Fuse Box Relocation, Wire Tuck, etc.

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    Registered User WRX13oy's Avatar
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    nice write up!!. i remember a while back on nasioc, someone ported their stock manifold and gained some hp but lost about 10 ft/lbs but he said the new sound it makes is well worth the loss in torque
    SOCAL F4#02 OG member

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    Registered User Wrinkleboi's Avatar
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    are you sure that wasnt with aftermarket headers? never heard of anything like that...
    bryan

    -2003 Blue WRX, complete 2007 STi Engine/Drivetrain transplant - Pic 1 | Pic 2 | Pic 3 | Pic 4 (new!)
    -1994 Black Supra TT 6MT - Pic | Build/Restoration Thread: 67mm, Fuel, Painted Engine Bay, Fuse Box Relocation, Wire Tuck, etc.

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    Registered User WRX13oy's Avatar
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    he compared the ported stock to the borla headers.
    SOCAL F4#02 OG member

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    Registered User Wrinkleboi's Avatar
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    ok still dont get what you're saying here... and nothing is worth a loss in torque. but porting the stock headers does not change their sound, nor does it cause a loss of torque so yeah... not sure what you're talking about.
    bryan

    -2003 Blue WRX, complete 2007 STi Engine/Drivetrain transplant - Pic 1 | Pic 2 | Pic 3 | Pic 4 (new!)
    -1994 Black Supra TT 6MT - Pic | Build/Restoration Thread: 67mm, Fuel, Painted Engine Bay, Fuse Box Relocation, Wire Tuck, etc.

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    Registered User WRX13oy's Avatar
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    here is the guys quote
    Quote Originally Posted by McBain
    Quick summary:
    The porting job was excellent. The 1/4" of iron that overlapped the gasket is now a polished, gradual taper. The car sounds a lot meaner without the Borla header. It is much deeper and less metallic and raspy. The graphs show that the turbo is spooling about 200rpms sooner than with the Borla. That doesn't quite live up to the hype, but it's better than nothing. I lost about 10 ft/lbs of torque, but the change in sound is worth it. I'd say if you can do it for free, you have nothing to lose. If you see just how much of an obstruction the overlap is, you'd want to remove it.
    i guess he was comparing the sound with the borla. hehe oops
    porting stock headers, yay or nay?
    and heres another good thread on port and polishing. http://forums.nasioc.com/forums/show...ht=port+polish this guy went port and polish crazy . im thinking of porting my stock manifolds too if it helps out with spool time.
    SOCAL F4#02 OG member

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  8. #7
    The Default One SeattleJeremy's Avatar
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    What kind of dremel did you use?
    What bits?

    EDIT: maybe I should re-read the first post

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    Registered User Wrinkleboi's Avatar
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    not sure if i mentioned it above... i used a makita die grinder with a carbide bit made for cast iron, then a grinding stone, then a flapper to smooth it out a bit. i didnt get too crazy with polishing it because you dont want it to be super super smooth. very smooth is plenty good
    bryan

    -2003 Blue WRX, complete 2007 STi Engine/Drivetrain transplant - Pic 1 | Pic 2 | Pic 3 | Pic 4 (new!)
    -1994 Black Supra TT 6MT - Pic | Build/Restoration Thread: 67mm, Fuel, Painted Engine Bay, Fuse Box Relocation, Wire Tuck, etc.

    www.TriStateTuners.com

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    Moderating on the run! Big Sky WRX's Avatar
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    Good job! I did mine last year- I bought a spare manifold and then did it at my lesiure (which was good because it took me a couple of weeks to finish )

    There is some "Frankenstein" casting seams throughhout the mainfolds that are worth smoothing out as well. I had a extension for my dremel and it let me get into them pretty deep.

    I too was very careful w/ the gasket matching- I didn't get too aggressive as it's hard to add back material

    As a finishing touch I had mine Jet Hot coated and then reused the factory shielding.

    You should see a quicker spool and low end torque will be improved. Good mod and the price is right!
    "Simplify and add lightness." - Colin Chapman

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    Registered User bluegdb's Avatar
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    i just did my last week.
    how much jet hot coated cost you?

  12. #11
    Moderating on the run! Big Sky WRX's Avatar
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    It's been too long to remember Give them a call (jet hot)- they've done lots of them I'm sure they can give you a accurate quote. There are other coaters out there too that might be worth looking into as well.
    "Simplify and add lightness." - Colin Chapman

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    Registered User osirissirhc's Avatar
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    quick question on the gaskets

    hey on thos exhaust man. gaskets are those reuseable or am i going to have to go and purchase a whole new set?
    Chris-
    05 STI- APS CAI, Apexi T-timer, BFG G-Force KDWs, Turbo XS catless turbo back, Perrin Crank Pulley, OPEN ECU tune, new ACT clutch kit and lightweight Flywheel
    13.6sec 1/4mile at 5,285ft elevation not on new clutch and FW
    BLOBEYE SYN...... #188

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