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  1. #1
    VinceGledhill is offline Head Mechanic
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    Nov 2001
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    Leeds, West Yorks, England.
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    How to Build your own exhaust manifolds.

    [h1]Build your own manifolds[/h1]

    After discussions with northern cobra club members on Sunday, and the recent post from Jesus in Spain, I thought I would explain how to manufacture your own exhaust manifolds from stainless steel. Or at least how I made mine.

    Disclaimer..

    These are not flow tested and will not give you every last bit of horse power. And if you've NEVER even seen a welder before then maybe you should think about paying for some.

    As you all know I'm a tight git. That's not strictly true but I have had to watch the pennies because I have a wife, two kids, and a large mortgage to support. This made me think about ways which I could save money during the build. The manifolds are a very expensive item, and discussions with other cobra club members in the northern area made me understand that I could indeed save some money on my build by making these myself.

    The engine you chose will dictate the size of pipes that you need to flow the exhaust gasses away. All I can tell you is that I used 1.5 inch (outside diameter) tubes on mine. (Rover 3.5 A friend of mine used 1.75 inch on his 5.7 chevvy)

    The flanges themselves can be purchased from custom chrome. However, when I ordered mine they were out of stock for two weeks. I couldn’t wait any longer and decided to have a go at welding the mild steel flanges to the stainless tube. This worked very well indeed and would recommend saving another few bob by going down this route.

    To start with, the body needs to be fitted to the chassis. Take one of your flanges and bolt it to the engine. I started with number 8 cylinder. The idea was that I needed to come out of the engine and then round in an S shape to where the collector would be. (this is where all four go into one)

    It was clear that the pipe needed to come out and immediately bend towards the front of the car. For this I used a 1.5 inch O/D dairy bend. Dairy bends come like the diagram below, with a straight section at both ends of the bend. One of the straights needed to be cut off in order to meet the clearance requirements of the body. I then marked where the first welds needed to be. I then removed the two items and tacked the bend to the flange. Once they were tacked in place I replaced them loosely onto the manifold. I double checked that all was OK and then welded it all the way round.

    The second bend within the S shape now needed to go on. Both straights on the two corresponding dairy bends were not enough for the distance that needed to be covered so a piece of flat tube was used as a “fill in”.

    I continued in this manner, building up a jigsaw of dairy bends and straights until I had a set of manifolds like in the pictures below. They were bolted to an old rover manifold so that the stainless steel didn’t warp during the welding processes.

    I used a “TIG” welder which is the ideal machine to weld stainless. I know what you are thinking… the price of the welder would make it not worthwhile…. However there are some reasonable welders available from Machine mart and this job will more than pay for your “TIG” set-up. I would recommend a TIG welder to anyone taking up this hobby. You can weld stainless or mild steel with it and it is much better than the cheaper MIG welders on the market.

    Dairy bends are available from RS components but are much cheaper from specialist suppliers like Hygienic Process Equipment Ltd. Hillside works, Whitehall Road, Cleckheaton, West Yorks, BD19 4DW, Telephone 01274 852752 http://www.hpe.co.uk

    To make a really neat job “weld good”. Alternatively if you are a learning welder like me, then use filler rod. Ensure that you have a proud joint. Then grind and sand out the welds later. Use successively finer grades of emery cloth then finally polish out with a polishing mop fitted to a bench grinder. One thing I will say about the polishing mop and bench grinder is to buy the best one that you can afford. There are about 5 different ones to chose from in machine mart. I bought the number 4 in terms of price (second to mose expensive... wot me... ) and thinking about it should have gone for the one with the most HP.

    The job is a very long one indeed. It took me three full days to do mine. This “labour” is what you are paying for when you purchase them from custom chrome or one of the kit manufacturers.

    The finished result will be in direct proportion to the time and effort you put into the job. I for one would definitely recommend the job to anyone who would like to save some money on their build and has the confidence to tackle the job. Let’s face it. If you believe you can do it, then you will find a way to make it happen.


    Regards
    Vince
    Time served Auto Electrician
    Lucas Leeds 1979-1983

  2. #2
    dax427 is offline Tyre Kicker
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    May 2002
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    Leeds, West Yorkshire, GB.
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    43

    RE: How to Build your own exhaust manifolds.

    Hello Vince

    Didn't get to talk to you much on Sunday.

    Nice to see I am not the only non cheque book boy (Technically know as a tight arse to those with lots of spare cash). Which model of the TIG welder did you buy from Machine Mart ?. How much do you reckon it cost to build the manifolds in total. Did you buy your actual side pipes from Custom Chrome ?.

    Regard's
    Paul

  3. #3
    VinceGledhill is offline Head Mechanic
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    Nov 2001
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    RE: How to Build your own exhaust manifolds.

    Hi Paul. I think about £550 including the welder. I got the most expensive (150 amp) one from machine mart. However I think the smaller ones would have done for this job. The largest current setting I had when welding was about 75 amps.

    The welder was purchased with other bigger jobs in the future in mind so went for the best one out of the bunch. I would have gone for an electric spark start model (press a button for the ark) but they were only available in 3 phase. Something I don't have in my garage.

    Regards
    Vince
    Time served Auto Electrician
    Lucas Leeds 1979-1983

  4. #4
    chesterak is online now Chief Engineer
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    Mar 2002
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    Chester
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    RE: How to Build your own exhaust manifolds.

    Vince,
    Thanks for the image editing advice...
    In support of what you are saying, I have made my own manifolds from 316 ss dairy tube and fittings. Including the mild steel manifolds, the total cost was about £180 and took me 3 weeks of evening work, however, I have a quite expensive TIG welder (Migatronic MTE 320) so I don't know how economic making your own would be if you have to by the welding plant as well. For anyone thinking of going down this route, I would emphasise the use of filler wire as without this the welds are prone to cracking. I've also decided to not polish out the welds so as to give that bit of extra strength.

    stan
    Stan

  5. #5
    VinceGledhill is offline Head Mechanic
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    Leeds, West Yorks, England.
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    RE: How to Build your own exhaust manifolds.

    Oops forgot the pictures

    Regards
    Vince
    Time served Auto Electrician
    Lucas Leeds 1979-1983

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