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Thread: Turbo Manifold

  
  1. #1
    Just a bit of BOOST
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    Jul 2014
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    Minot, ND
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    Question Turbo Manifold

    Anyone have any good recommendations on a t3/t4 center position manifold for an '84 SVO? The manifold that was on my car when I bought it got a large hole and a crack on it that was repaired twice before I replaced it with one from stinger performance, that one lasted about 400miles until it cracked, so I put a flex pipe after my down pipe, had the crack welded and reinforced. That lasted about 100miles before another crack formed next to the first one. Another weld and about 20miles later it cracked again and created a small hole. Because of how my turbo tubing and oil lines and exhaust is setup (all custom work) I can't afford to lose the position of my turbo so I need a header that looks like the generic knockoff header from ebay (the equal length with wastegate). But is reasonably strong. I haven't been able to find one, the cast iron one from gnari seems to be what people lean towards but that would require me to redo a lot of things on my car for it to work right. I can try to get one custom made but I'd like to know if anyone has found a decent one, and if not, what size tube wall and tube material would be the best for a custom one.

  2. #2
    OVER-BOOST!! dagenham's Avatar
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    Sep 2005
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    SVO's: '84 9W
    What is causing the manifolds to crack in the first place? It sounds like there is another problem besides the manifold.

  3. #3
    OVER-BOOST!! svono50's Avatar
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    SVO's: 86 1C
    My guess on the cracking manifold is a three-fold issue: 1) material choice, 2) material gage/thickness and 3) design. A lot of aftermarket headers are made of thin gage metal of either mild steel or lower grade SS. These materials work fine for an N/A application (usually), but hang a turbo off the end of it, even with supports, and you end up with all kinds of bending stresses on the tubing that kill it in short order. Another issue is proper pre-heat, stress relieving and filler material for the weld. I think the 'log' style headers that use heavy gage SS fittings/tubing (i.e.- Bob's log headers) seemed to hold up much better than the thin-wall examples, but they are not without some issues as well. I am not even sure if you can get a Bob log header any more, has been a while since I have seen any talk about them, but they seem to show up on various forums/Ebay and the like on occasion.

    Since I am still running the stock manifold, I can't help much more. I am sure some folks on here running an aftermarket header can chime in to give some input. Good luck.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  4. #4
    Just a bit of BOOST
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    Sorry for the late reply.
    I think the reason the manifold cracked in the first place was because I got a megasquirt ecu and paid "some guy in a back alley behind an autozone" to tune it, in hindsight this was a terrible idea as I went through about 12 spark plugs and a headgasket in a 2 week period before getting a proper tune, I ended up replacing the engine with one from a T-bird because the old one was FUBAR. It ran really rough and would constantly alternate running lean and rich, would never build more than 5lbs boost before losing all power, the tune fixed all of that. The manifold was from the old engine and I put it on the new one, then it cracked.

    After coming home late one night I could see the manifold was glowing a nice red-orange after some mildly spirited driving (on old tune, old engine). I think that was the start of the problems to the manifold. It must have gotten so hot that it got weak in a spot and just went downhill from there, the material used for the manifold is SUPPOSED to be 0.065 wall thickness and T409 steel but who really knows coming from china.

    There is no excess weight on the manifold, I have brackets on the downpipe that allow for flexing while still keeping it held up, I also have a flex pipe after downpipe.

    Its cracking on the top side between the wastegate flange and the turbo flange, there shouldn't be much pressure in that part of the manifold. If I get some snow moved in the next few days I'll dig her out of the garage and take some pics so you can see exactly where its cracking, maybe its something unrelated to the manifold.

  5. #5
    OVER-BOOST!! svono50's Avatar
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    Well, the 'bad' tune you had in there was likely putting a lot of heat cycle stress on the manifold, not doubt about that from the sounds of it. The material thickness on the 'log' style headers is generally in the 0.200" range, so your header is really a pretty thin material for a turbo application. If the source for the header was China, all bets are off on the composition/quality of the material. Now you could be over supporting (i.e.- constricting) the manifold and causing the expansion of the material to buckle trying to fight the support brackets. I am sure there is a pretty straightforward reason for the cracking...solving it may be quite difficult though.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

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