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Thread: Headers

  1. #1
    Senior Member Don's Avatar
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    Headers

    Damn;

    I just typed out a long winded question and the damn thing seized on me..... Arggg!!!!

    Anyway, here I go again.

    Headers. I am having trouble finding a front manifold for the 3.4 DOHC to replace the rear one as I want to run teh exhaust in th estock Fiero route versus out the rear side of the engine so I decided I would build a set of headers for it instead. I now have a decision to make around what type of header to build versus power increase, sound etc.

    I have done some reading on the web around the design aspects etc. and I have narrowed down to 3 options in my opinion for headers.

    • Log Headers. Essentially, build a header set that look a lot like the stock 2.8 manifold or 3.4 exhaust manifold where each port comes out into one tube running into the connector/crossover pipe into the rest of the exhaust. Easiest to build, and you get some hp increase from removing the stock cast manifold restrictions but not a lot.
    • Shorty Headers. A lot like the log style but each port runs into a collector so you remove the mixing and backpressure from the other ports with the log style. You still have unequal length primaries so you don't get optimized tuning. More difficult to build than log but you will get more hp increase. Not sure how much to expect.
    • Long Equal Length Headers. Best of the bunch but much more involved in designing to the proper rpm range, peak torque curve, with more complex bends to make sure all are equal legth both sides of the engine. I have to assume it wil give the best sound and hp increase since you are tuning to optimize for road or race performance. Whatever your preference.


    Obviously, the long headers would seem to be the obvious choice overall but my question is: Is it worth the extra work to build these for what you will gain in hp and sound etc.? I have read that tuning these long headers can be a lot of work after installing to make sure you compensate in the ECM etc. for fuel, air against the more free flowing and tuned headers. I had not planned on porting the heads or intake at this time as I want to get the engine in and working to start with. I can always play during a later winter when it is stored.

    Thoughts?

    Thanks
    Don
    308 Ferrari replica
    Prova Countach 5000QV

  2. #2
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    Re: Headers

    if you go with building the long tube or shorty headers, you might want to start with a set of premade headers and just modify them to what you need. On the tube chassis, (I'm still planning on buying from you) I'm planning on ordering a set of used f430 headers from ebay, then modifying the bolt flanges to bolt up to my Aurora motor.

  3. #3
    Senior Member RCR's Avatar
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    Re: Headers

    Honestly Don, for the gain you are going to achieve and believe me, I know how these projects go, mine is the same way, I would just port the stock manifolds. Unless you are looking at doing a personal challenge (that's what gets me in trouble), I would concentrate on getting it running and finished. Then throw the speed stuff on it, headers, ported intake/heads, etc.

    Bob
    Bob custom '84 Fiero SE --->>> custom F408
    http://www.madmechanics.com/forum/cu...ilepic37_1.gif

  4. #4
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    Re: Headers

    found you a set of manifolds, if you wanted you could ship them to me and I would bring them to you when I pick up the car. Keep you from having problems with them not wanting to ship out of the states.

    http://cgi.ebay.com/ebaymotors/GM-3-...4506.m20.l1116

  5. #5
    Senior Member Don's Avatar
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    Re: Headers

    Thanks Bob;

    I have been pushing toward getting it in and running so I can move on to other items. I have all the tubes for the headers and I did not get a cross over pipe with the engine so I think at most, I will build the shorty headers into the cross over pipe in the stock location and into 2.5" pipe from that point.

    James;

    These headers are from a '92 so the ports are different than the '96 so they won't work. This is what I have been finding as well where the manifiolds I can find relatively easily are for the earlier engines....

    Thanks for the feedback guys.

    Cheers
    Don
    308 Ferrari replica
    Prova Countach 5000QV

  6. #6
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    Re: Headers

    Have you checked here? http://car-part.com/index.htm

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