Making an exhaust

  1. BRODTuning Member

    Messages:
    128
    south wales
    Hi lads, ive got a 2litre 8 valve nova that im building which will hopefully be on the road by november ish time. Ive got a magnex 4 branch that i had with my new engine. I was planning on making a flange of sorts and buying a full magnex system for it but i thought id spare myself some money and make one. First question is what grade of stainless is ideal? 409? 316l? ...another question is how can i identify what grade my manifold is, or what filler could i use that will work? It doesnt have to be expecially strong as it will probably just end up being two tacks to hole the flange. Any advice is welcome!
    Brad.
     
  2. hotrodder Member

    Messages:
    4,587
    SE England
    OE manufacturers favour 409 when they use stainless over coated mild steels, the 4xx series stainless steels are magnetic unlike the 3xx series. The aftermarket (including Magnex according to their site) tends to favour 304. 316 only really gets used because 'hygienic' stainless fittings are made from it and hygienic bends from a proper stainless stockholder are typically cheaper and better quality than bends from an exhaust manufacturer.

    304 is best welded with 308L, 316L is also often used*. 409 is usually welded with 309L. 309 is also used for dissimilar joints such as mild steel to stainless etc. More here... http://www.mig-welding.co.uk/stainless.htm

    *There are applications where doing so is a bad idea but for a lot of stuff (exhausts for example) it doesn't matter.
     
  3. langy

    langy langys rodshop

    Messages:
    6,099
    Location:
    London
    I make all mine in 316L
     
  4. Terrapin Member

    Messages:
    72
    UK Wirral
    321 or 304 preferably. Inconel if you are flush :laughing:

    I usually do the dry run in mild steel as it can involve a lot of messing about on the vehicle. Then fab up the finished item in ss etc. It can save you money in the long run as mild steel bends and parts are relatively cheap.
     
  5. hotrodder Member

    Messages:
    4,587
    SE England
    For a turbo manifold 321 is better than 304/316, it's also a lot harder to find and a lot more expensive. For a naturally aspirated system i'd say it's overkill unless weight is super important and you're wallet is too heavy to pick up. If that's the case then inconel will let you make a stupidly light manifold (that's also very delicate due to the crazy thin wall thickness you can get away with) and, as we're dreaming, Ti for the rest of the system as while it won't handle the heat a manifold has to endure so well it's almost half the density. Just need to win the lottery :laughing:
     
  6. langy

    langy langys rodshop

    Messages:
    6,099
    Location:
    London
    Mild steel bends are only a quid cheaper than stainless bends, why would you do the job twice ?
     
  7. BRODTuning Member

    Messages:
    128
    south wales
    Thanks for the help all...ill read over everything again when im not ******ed, hahaa. Ill be bending it all myself and making it all from straight tube anyway with the hydraulic bender, also have a manual hydro one too so it shouldnt be a problem. Im looking at 5 maybe 6 bends at absolute maximum! it depends how i decide to route it and if i want to raise it slightly. Confident i can make it in one go rather than make a mild pattern first, might just end up breaking some tacks and cleaning off. Eitherway, no big deal :) considering purging but not quite sure if i can be arsed as im using my uncles machine.
     
  8. Terrapin Member

    Messages:
    72
    UK Wirral
    You must be paying a lot for your ms bends or your ss is very cheap :laughing:

    Joking aside, if it's a straightforward job with easy access then I agree with you. If it is tight access, complex bends with lots of angles then I mock up in ms and then use it as a pattern for final ss version.
    I can get ms bends for next to nothing from my supplier.
     
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