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head work//

Discussion in 'Engine Building' started by Sergey P.A., Dec 28, 2003.

  1. Sergey P.A.

    Sergey P.A. Senior Member

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    ok, can somebody explain to me what's a 3 angle valve job and what it does, and what's a 5 angle valve job, what's the difference,

    and what about the porting and polishing=I know what it is, but how much you port on a GSR head and do I have to port bouth ports or jest the IM inside?=I know that this will make the GSR head flow better/right, so will it make the GSR head be close to the P75/PR3 head?

    and what else you do to the head?

    do I have to buy an after market IM in order to polish it, ?

    and if I do all that what should I exept from this MOD, will it gain HP all the way through RPM's or jest the top end?

    ? :)
     
  2. pissedoffsol

    pissedoffsol RETIRED

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    your standard 3 angle is a 30/45/60 degree, i believe the five is 15/75 as well to aid flow. Pretty much standard stuff for the 3 angle, doing a 5 helps more on a smaller valve and low lift, where as the 3 angle is good for high lift cams and or larger vlaves. The 3 angle cut bumps your low lift flow numbers dramatically over a std 45 degree single cut, which is a real big deal on turbo cars. As far as the variation of valve angle question.... some angles work better with certain port/valve designs than others, but without having someone who has put the flowbench time in on your exact combination I don't think there is really any gain you will see by swapping to angles other than the standard 30/45/60. If you are looking for more flow without putting in a ton of flowbench time, backcut the valves and add an 80 degree bowl cut and you will see a couple CFM more. IMO for the money, a standard 3-angle is all you need.

    porting should be done by a machine shop with a flow bench. toherwise, you could make it worse
    polishing is just that- polishing... makes it "smoother"

    gsr will never be a p75- that's an LS
    pr3 is a b16, and it too will enevr be a b16 head. the combustion chambers and so much more are different.

    furthermore, saying a b16 head flows more than a gsr head is simply not true.
     
  3. cointelpro

    cointelpro Senior Member

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    ive heard you should not polish your IM as much, if any, as your exhaust mani because the rougher surface will allow the gas/air mixture to linger for a bit (i dont know why this is good) but when i saw the video (yes i watched a PnP video) they bumped the flow from 80 percent to 92 percent with that method. and no you dont have to change your manifolds to pnp them. IMO pnp and all that is something you should only do after all your other mods.
     
  4. JDMilan

    JDMilan Senior Member

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    the fuel and air mixture combines just about before the head ports so I would assume that some extrude honing will do some good for the majority of the intake manifold.


    also, just wanted to use this :buyanm:
     
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