Modifying cast iron manifold requiest for opinions

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I just took in a project for a car builder for modifying a v-10 engine's exhaust manifolds.  I do cast iron repairs periodically.  While not a repair per se, this one involves cutting the collector of a cast iron manifold and rotating it 90 degrees.  This needs to be done because the car being built (based on a 1940 ford sedan body) does not have the space to attach the exhaust pipe in its present position.  It must point straight back instead of outwards.  A custom exhaust system will be fabricated to mate to the modified manifold once installed in place.  The client will smooth out and blend in the weld once done.When I do cast iron repairs (torch or arc welded) my general rule of thumb is that if the joint is in a position to expand and contract freely I do not pre-heat beyond taking the chill out of the piece prior to welding.  Thus if a cast iron block breaks a starter mounting hole (for example), I will simply build up the area with torch and bronze, drill and tap it.  Period.  However if the piece is part of say a stiffener inside of more complex part, I will either heat it up entirely and weld it hot and allow it to cool slowly or will cold weld it with small 1/2" beads at a time until done never letting it get hotter than I can put my bare hand on it.I plan to make a straight cut parallel to the flange, rotate the collector 90 degrees, bevel it and weld it out with some type of ni-rod.  Questions:1) Am I correct in just welding it out in one shot or should I do it in small beads as described before or heat it entirely and weld it hot?2) Can I "butter" the bevel with ni-rod and then weld it out with a mild steel rod such as 7018 or go all the way with nickel?Any thoughts, advice, things to watch out for?  Pictures attached.Thanks in advance,Tony
Reply:Why not use something like this- http://gibsonperformance.com/product...t_number=GP304
Reply:Get the truck manifolds, he'll probably save money and have something that won't more than likely break
Reply:If it were mine, i'd nickel it all the way. 1/2-3/4" at a time and peen the snot outta each weld with your slag pick before it cools.I would also preheat somewhere in the mid 200's and slow cool after welding.
Reply:i did a cast alteration a very long time ago and it's still holding. a friend's boat engine manifold cracked at the bolt on connection so i made a steel profile the same shape as the cast on both sides welded the cast to steel with 99 ni rod. (don't remember the brand/make) then mated the halves together and welded the steel to steel joint with 7018.i.u.o.e. # 15queens, ny and sunny fla
Reply:Hi all,Thanks for the feedback.  I was really torn between going with the ni-rod or brazing.  I opted for brazing after viewing a tutorial on welding cast iron by the "Lock and Stitch" people who use threaded overlapping studs to seal a break in cast iron.  Anyway there was a link to their site in one of the threads I researched = http://www.locknstitch.com/CastIronWelding.htm.  This presentation made the argument that brazing was better than welding.Together with many other articles I read about cast iron manifolds being successfully repaired with bronze and torch.  I sill usually ni-rod a manifold.  This was the exception.  I hope it works out well in use The car is being built as a show car so I took a gamble that it will not be put under extreme use that will stress the brazed joint beyond its limits.  It will not be a daily driver type of car, most likely to be ferried around in a trailer or so I hope.  However I took comfort in that article after article that I read about successful cast iron manifold repairs.Anyway,here are the pictures of the finished project.  This is the first side and tomorrow I will start on the other side.  After twisting it I had a gap in some places due to the angle change when I lined it up square with the flange in both directions.  I tacked it in place using my mig then heated it to 400 degrees then started to weld it out rotating it as I went.  It filled in easily once I got the puddle flowing.  I built up more than was needed in some areas so that it could be ground down and contoured to hide the joint.  I put it into a box filled with cat litter to let it cool slowly.  Once its painted or coated, it should be invisible to the untrained eye.Thanks again,Tony Attached Images
Reply:That is a darn fine looking braze joint. excellent prep and obviously skilled use of the brazing torch. Happy Holidays!
Reply:IF it were my project, I would have you braze it up like you did. Then send it off to a foundry and have them cast it new. Then it would truly be worthy of show!Just my opinion. And in the world of my opinion, the cost is not a factor. hahahahLincoln Power Mig 210MP MIGLincoln Power Mig 350MP - MIG and Push-PullLincoln TIG 300-300Lincoln Hobby-Weld 110v  Thanks JLAMESCK TIG TORCH, gas diffuser, pyrex cupThermal Dynamics Cutmaster 101My brain
Reply:I'd have just build a header. In my opinion that is going to end up back in your shop, and likely more than once, and for free too.
Reply:Originally Posted by walkerI'd have just build a header. In my opinion that is going to end up back in your shop, and likely more than once, and for free too.
Reply:Hi all and thanks for the feedback and opinions.  I did the second one yesterday.  In view of the possibility that the bronze won't hold up I was thinking of welding a flat bar on the backside connecting the two parts using ni-rod to give it structural strength to counter the possibility that this joint could fail under the heat of the manifold in use.Do you think that would work?  I did not have a way to keep this under heat while welding it and because I had significant gaps to fill I was worried that I would be putting too much heat into the cast iron that would not be offset by keeping it at temperature.  The bronze approach provided a slower heating process that was not so dramatic.Using hind sight maybe I could have placed it on our propane mobile stove (we use for cookouts in the back yard, etc.) and have it under continuous heat while I arc welded it.  Would that have been a better approach to take?If push comes to shove, I can cut it and grind the bronze off and redo it in that fashion.  You live and learn.Thanks,Tony
Reply:Did you use that cutting torch for cutting? If it worked you may be dealing with cast steel, not iron.
Reply:I think you did a very good job. Bronze will hold as good as nirod with a good job. and I could tell by the looks that you never got it to hot.  Ive been doing them that way since the mid 50s.  some of the early cast Iron manifolds like the 46, 47 chevy six were pored out of some kind of shi-y cast Iron that you couldn't do much with.  Mac
Reply:If it really is a show car only, then it ain't going to fly simply because it is a crude method to modify a manifold. If it gets used then it isn't going to fly because of abuse the big motor is going to put on a brass joint. You would have been better off to. Build a flat flange and weld it to the bottom to bolt to. And much better off to have built a header.
Reply:Hi all,thanks for the kind words and critiques.  This modification was done at the car builder's request.  I had never done one of these before and my experience with exhaust manifolds is limited to small repairs (cracks mainly).  The thought of building a set of headers never even entered my radar probably because I've never built any and I didn't have any reference point to guide me.  The builder is going to smooth out the weld and blend it in.  My take is that he is going after looks more than performance because if it were intended to be a high performance vehicle, the modification I did to the manifold would throw off whatever engineering went into the design as far as the scavenging effect, velocity, etc.  The modification shot these all to hell.That being said I can honestly say that I did the best I could to meet the client's request.  He liked the modification and it has eliminated a road block as they were waiting to solve the manifold issue so they could work on the rest of the exhaust system.For future such projects should they come up I will make it a point to look into how to go about building a set of headers although form what I've read over the years, headers tube lengths are designed to be even so that the scavenging effects are done in a balanced way.  For me this would be like a "do it yourself" type of project as I am not a pro and I would be moving at a snail's pace very trial and error.  Not the best way to do it, I most likely would have to turn such a project down.  I suppose I could always look into who does that type of work in my area so I could refer a client to them.  I do this with rim repairs as there are some such repairs that I am unable to do because I don't have the right equipment to do so.  I regularly refer people to other shops when a repair is beyond my capabilities.The manifold is cast iron.  The torch was in the pictures as I had it ready to heat up the part prior to welding it out.