Rubce Posted January 13, 2013 Share Posted January 13, 2013 Hi AllHave any of you got experience of repairing the mating faces of a cast iron exhaust manifold where it matches up to the head? The manifold off our GT6 is worn in the areas adjacent to the centre four ports. Is welding and then re-machining an option? I briefly considered replacing it with a tubular manifold until I saw the prices Rimmers are asking!RegardsBruce Quote Link to comment Share on other sites More sharing options...
piman Posted January 13, 2013 Share Posted January 13, 2013 Hello Bruce, how much is the wear, I would suspect not a lot so just re facing the flange would do the job? Alec Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted January 13, 2013 Share Posted January 13, 2013 Welding cast iron is a bit tricky. Manifolds are not rare or expensive so probably easier and cheaper to get a better replacement. Have a few kicking around here though most need stud surgery.....Nick Quote Link to comment Share on other sites More sharing options...
Paudman Posted January 14, 2013 Share Posted January 14, 2013 If it's only cleaning up a face and then skimming flat then a bit of chemical metal will do the job, there are high-temperature versions out there. I'd be prepared to redo it every so often though. My own MK1 manifold split in two halves on a run back from Scotland, the only solution was to buy a tubular version as I was advised welding would be nigh-on impossible. Quote Link to comment Share on other sites More sharing options...
JohnD Posted January 14, 2013 Share Posted January 14, 2013 Bruce,So many people have gone for a tubular, and the originals are normally bonb-proof items that will survive anything that wrecks the rest of the car, so that there must be many unused cast-iron manifolds sitting in back-garages. I'm sure I have some!If yours is damaged, chuck it and get another, don't repair. There are two on eBay right now, one for £5 and one for £50. (Lunatic! Where do people get the idea that these things are gold dust?) Is your engine Mk1 or II?John Quote Link to comment Share on other sites More sharing options...
Richard B Posted January 14, 2013 Share Posted January 14, 2013 MkI cast manifolds are getting scarce due to their fragility. If its a MkI consider a tubular version.MkII cast manifolds are stronger, and therefore more plentiful and cheaper.I gave up trying to weld a lasting repair to a MkI manifold. Might have been better with Oxy-Acetalene. :-/Just read your signature (if it's a MkII manifold for the MkIII GT6) you should be able get a replacement for around £15 as John (above) has stated. Quote Link to comment Share on other sites More sharing options...
JohnD Posted January 14, 2013 Share Posted January 14, 2013 I remember some time ago reading an explanation of the difficulty of welding cast iron.It's all down to the alloys in the various cast irons, and the best advice is that the native metal must be heated as high as 500C to avoid cracking or and to allow full penetration of the weld. Not easy to do with something as big as as a manifold.John Quote Link to comment Share on other sites More sharing options...
piman Posted January 14, 2013 Share Posted January 14, 2013 Hello John, I've done a few cast iron welding jobs all without pre heat but you do need the correct rods. It is even possible to weld mild steel to cast iron , e.g. to patch a hole, again with special rods. AS Richard mentioned, oxy acetylene is an option to float some brass over the depression. Alec Quote Link to comment Share on other sites More sharing options...
Richard B Posted January 14, 2013 Share Posted January 14, 2013 Yes, brazing rather than welding. Quote Link to comment Share on other sites More sharing options...
Gt6s Posted January 14, 2013 Share Posted January 14, 2013 JohnD wrote:I remember some time ago reading an explanation of the difficulty of welding cast iron.It's all down to the alloys in the various cast irons, and the best advice is that the native metal must be heated as high as 500C to avoid cracking or and to allow full penetration of the weld. Not easy to do with something as big as as a manifold.JohnNot just that, the item needs to be cooled down slowley and evenly it is in the cooling process cracking occurs.Laurence Quote Link to comment Share on other sites More sharing options...
Gt6s Posted January 14, 2013 Share Posted January 14, 2013 JohnD wrote:I remember some time ago reading an explanation of the difficulty of welding cast iron.It's all down to the alloys in the various cast irons, and the best advice is that the native metal must be heated as high as 500C to avoid cracking or and to allow full penetration of the weld. Not easy to do with something as big as as a manifold.JohnNot just that, the item needs to be cooled down slowley and evenly it is in the cooling process cracking occurs.Laurence Quote Link to comment Share on other sites More sharing options...
JohnD Posted January 14, 2013 Share Posted January 14, 2013 Orl Korrect, as they say, but expensive.Get another manifold, Bruce!John Quote Link to comment Share on other sites More sharing options...
ferny Posted January 14, 2013 Share Posted January 14, 2013 JohnD wrote:and the originals are normally bonb-proof items that will survive anything that wrecks the rest of the carI've managed to kill a couple of 13/60 manifolds and a couple more 1500 Spitfire ones on various engines and in different places. :B Quote Link to comment Share on other sites More sharing options...
mikew Posted January 14, 2013 Share Posted January 14, 2013 ferny wrote:I've managed to kill a couple of 13/60 manifolds and a couple more 1500 Spitfire ones on various engines and in different places. :BNot surprised with your bodged up exhaust systems ;D Quote Link to comment Share on other sites More sharing options...
Rubce Posted January 14, 2013 Author Share Posted January 14, 2013 Hi ChapsThanks for all the responses. This Forum is great!Is there any reason why I couldn't simply have the manifold flashed over on a grinder? RegardsBruce Quote Link to comment Share on other sites More sharing options...
GT6Craig Posted January 14, 2013 Share Posted January 14, 2013 Be better on a belt sander :-/ Quote Link to comment Share on other sites More sharing options...
Rubce Posted January 14, 2013 Author Share Posted January 14, 2013 184 wrote:Be better on a belt sander :-/Why? Quote Link to comment Share on other sites More sharing options...
nicmk1est Posted January 14, 2013 Share Posted January 14, 2013 this may help you with cast iron repairs---theres a link to how tohttp://www.mig-welding.co.uk/forum/showthread.php?t=27676 Quote Link to comment Share on other sites More sharing options...
ferny Posted January 15, 2013 Share Posted January 15, 2013 mikew wrote:Not surprised with your bodged up exhaust systems ;DOi, you cheeky fecker! The Acclaim's system is spot on now and the mpg has gone up by two. :)The Herald... well... I've given up sealing it since it always gets pulled apart on the same speed bumps. :-/I've not broken a manifold since I tinkered though! :P Quote Link to comment Share on other sites More sharing options...
DaveKent Posted January 15, 2013 Share Posted January 15, 2013 i've taken many a head and block here for my customers. not your cheapest option inthis case but they do a proper job.http://www.castironwelding.co.uk/ Quote Link to comment Share on other sites More sharing options...
piman Posted January 15, 2013 Share Posted January 15, 2013 Hello Bruce, I refer the honourable gentleman to the answer I gave earlier (Post 2)Alec Quote Link to comment Share on other sites More sharing options...
GT6Craig Posted January 15, 2013 Share Posted January 15, 2013 Quote:Quote:Quoted from GT6CraigBe better on a belt sander Why?Where you suggesting angle grinding the flange face to remove pitting?The bed of a table belt sander (even them little ones from B&Q) give a relatively flat surface to “work out” minor pitting…I have seen a good finish from linishing a manifold flange face on one.Just a thought….obviously milling would be the best and recommended option. Quote Link to comment Share on other sites More sharing options...
piman Posted January 15, 2013 Share Posted January 15, 2013 Hello Craig,"I have seen a good finish from linishing a manifold flange face on one"I don't doubt you'd get a good finish but it takes a lot of skill and care to get an accurate finish.It's a small job to mill the face, that's what I would do if I had to.Alec Quote Link to comment Share on other sites More sharing options...
Rubce Posted January 16, 2013 Author Share Posted January 16, 2013 184 wrote:Why?Where you suggesting angle grinding the flange face to remove pitting?[/quote]No I meant a surface grinder, not an angle grinder :)RegardsBruce Quote Link to comment Share on other sites More sharing options...
Rubce Posted January 16, 2013 Author Share Posted January 16, 2013 piman wrote:Hello Bruce, I refer the honourable gentleman to the answer I gave earlier (Post 2)AlecHi AlecI think you are right. I have made arrangements to take it to our local machining company at the weekend.RegardsBruce Quote Link to comment Share on other sites More sharing options...
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