modifying a cast iron exhaust manifold-advice requested.....

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Hi all,I posted this under welding projects but received only one response suggesting I purchase a set of headers configured the way I need them.  I am looking to modify a new set of manifolds.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.Am I correct in assuming that this joint will be free to expand and contract freely as the newly joined collector will be "floating" free to move upon expansion and contraction of the welded joint?  Or should I pre-heat the manifold and keep it hot during the welding / brazing process?  Then cool slowly.  I've read several postings regarding repairing cracks on exhaust manifolds but this project is different than those I read (keep it hot, weld and let it cool slowly, uniformly).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.   I am also thinking it could be brazed.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?3) Can I braze the parts back together?  Will the bronze hold up under the heat generated by the exhaust?Any thoughts, advice, things to watch out for? Pictures attached.Thanks in advance,Tony Attached Images
Reply:Your probably going to have a bad time given that the exhaust hangs on the manifolds and it's going to see a lot of vibration and heat cycling. I think welding this on the weber grill with full preheat and good nickle rod is the best way to do this. Then wrap heavily with mineral wool and let it cool very slowly.If that doesn't work he might be looking into getting a set of headers made up. Any idea what motor is going in? If its a more modern V10 the right manifold might already exist. Kinda looks like a Viper manifold, the truck manifolds are rear dump.
Reply:"I plan to make a straight cut parallel to the flange"Are you sure you mean PARALLEL?I'm thinking you mean PERPENDICULAR.Or maybe I'm just not getting what your intent is.I photoshopped your images to illustrate how I interpret the two different terms and how that affects the results. Attached Images
Reply:Originally Posted by walkerweld"I plan to make a straight cut parallel to the flange"Are you sure you mean PARALLEL?I'm thinking you mean PERPENDICULAR.Or maybe I'm just not getting what your intent is.I photoshopped your images to illustrate how I interpret the two different terms and how that affects the results.
Reply:Ordinarily I like braze welding, but in this instance I'd make certain that the operating temperature for that manifold isn't too high for a braze joint.  Even if you're well below the melting temperature of the braze filler metal, the high temp environment could cost you a lot of strength.  Couple that with a load from the down stream exhaust system, cyclic thermal stress, and vibration stresses, and you might not get the performance you want or expect from a braze weld.I'm just looking at the worst case, mind you.  Selecting the right brazing filler metal will help.  It might also be that this manifold won't get as hot as I'm imagining...Just some food for thought.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Check out Palco Welding Supply cast iron rods. Have never used them, but this may be a solution.
Reply:Originally Posted by guajilloweld03Check out Palco Welding Supply cast iron rods. Have never used them, but this may be a solution.
Reply:Why not just make a set of REAL stainless headers?You can get a kit and it will probably be alot easier to do than what you are trying to do......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterWhy not just make a set of REAL stainless headers?You can get a kit and it will probably be alot easier to do than what you are trying to do......zap!
Reply:I have not heard of anyone doing this since my grand father and father split manifolds for jalopy racing before WW2 or after It was a time consuming task involving pre and post heating and slow cooling using blow torches and fire bricks And all night of working to get it rightSent from my SPH-D700 using Tapatalk 2Backed my CATMA over your CARMA oops clusmy me  What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite  Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:Ok man, are you saying that you weren't sure which side header it was at first? Seriously? My eyes are spinning from reading that! What! Exhaust does not blow out of the front of a car. Never. I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Originally Posted by weldermikeOk man, are you saying that you weren't sure which side header it was at first? Seriously? My eyes are spinning from reading that! What! Exhaust does not blow out of the front of a car. Never.
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 brazed 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. Start to finish it took three hours not including the cool down time soaking in the cat litter box.Thanks again,Tony Attached Images
Reply:It seems to be coming along nicely.  The realignment of the runners in the collector area looks to be better than what I thought it would (considering that the runners join somewhat asymmetrically in the OEM configuration).
Reply:GEE!Maybe weldermike needs to GOOGLE "ford flathead v8" and see where the RIGHT HAND exhaust does indeed BLOW OUT THE FRONT!It crosses over on the front to connect to the left side then flow through to exit the rear of that manifold.Know this for a fact as the neighbor had 2 go through his shop this past summer.
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:Hey the modification looks pretty darn good to me. I know bronze is not as strong as the nickle arc rod and in this particular spot it does need to support some weight and vibration as well as 1000 plus deg exhaust temps. To support the joint you could fashion a piece of flat bar on the back side and tack it up with the nickle rod. Back side i mean opposite of the exhaust opening. If you think about it the engine twists under torque to the right so may be opposite forces on each side.Fireman BillHH 210 MVPMM 211 Spoolmate 100Lotas LTP5000D PlasmaOxy/Accet (Victor)Wards AC/DC buzz box30 ton old hyd pressA few brand name toolsA bunch of cheap toolsA wife to worry me and4 dogs to supervise me
Reply:For future info: Did you cut that with the torch there and tack weld it with steel?  If you could cut it with a torch, my guess is it is cast steel and not cast iron.
Reply:that looks like a kick-a$$ repair. did you say you tacked it with the mig? did the tacks hold ok while you were brazing?i.u.o.e. # 15queens, ny and sunny fla
Reply:That is a very nice braze job indeed! Some years ago, I was asked to help a friend repair an exhaust manifold for a four cylinder Mercury (Capri?). It was broken off in the same place as shown in the above pictures where the cut was made to re-rout the exhaust. I cleaned the area at the break and beveled it 45 degrees all around with a sidewinder grinder. Then we heated the parts for about 15 minutes with a rosebud tip until they were very hot. I have no idea how hot but I was sure that it was preheated enough. It was near red at the weld area before I started my repair.  I brazed it with a large tip and the bronze rod flowed very nicely. The repair went very well and when we were done the part was picked up with a C-Clamp and buried in sand until the next morning. The owner of the car re-installed it and as far as I know it was still holding when he sold it some years later. I would always use brass or bronze for a gas repair since I'm familar with it. I understand that ni-rod works very well but I've not done any of that. The key is to do sufficient pre-heat and after the repair, arrange to have the part cool down very slowly. Since I did that repair, I built a very large powder coat oven (36" X 24" X 72") for doing motorcycle frames and car and bike rims. It will go to 500 degrees if needed. If I do another such braze repair, I'll tack first and then do the preheat in the oven. After the weld/braze, I can put the part back in the oven to keep the heat up as long as needed while lowering it over a period of hours if need be.Last edited by gnm109; 12-22-2013 at 10:10 PM.Miller Millermatic 252Miller Syncrowave 200Liincoln AC-DC 225Victor O-A Set
Reply:Hi again.  Thanks for the kind words.  I always liked torch welding especially brazing.  When the puddle gets going you get into a rhythm and it just flows out of you like music does to a musician.  Anyway.  I cut it with an angle grinder and 6" cut off wheel after I transferred a layout line from the table onto the collector with a small square making a nice straight line to follow with soap stone.  The torch is seen in the picture as I had it ready to apply heat once I got it all lined up ready weld.It is cast iron and not cast steel.  The nature of the sparks (sparse and a faint yellow / orange ) are typical of how cast iron reacts to a grinding wheel.   It is soft to the grinding wheel and wears down easily as well.  The mig tacks held just fine.  Since I had heated the whole piece prior to the brazing, the metal would have expanded evenly, tacks and all.  I found that tacking them was a big help as opposed to just lining it up, heating and starting to weld because in order to hold it in place I was using some of those magnetic triangular square hold downs as well as some vice grips and angle iron which would have had to be subjected to the heat had I not tacked it.  This way I could remove those things from the heat zone and just concentrate on the brazing. I like the idea of having some type of oven to do these type of projects and I will put it on my "to do" list.  The right tool for the job is a true fact of life.Thanks,TonyLast edited by therrera; 12-22-2013 at 11:09 PM.Reason: to add more detail
Reply:On the subject of preheat and post heat methods, one of those "weed burner" propane torches can do a good job of heating large objects fairly evenly and quickly.A gas barbecue grill is also nice, as was mentioned.
Reply:Originally Posted by walkerweldOn the subject of preheat and post heat methods, one of those "weed burner" propane torches can do a good job of heating large objects fairly evenly and quickly.A gas barbecue grill is also nice, as was mentioned.
Reply:"Tell tale" temperature sticks are good.  You can also use a "laser guided", non contact infra-red thermal scanner to check the temperature at will.  By placing the laser targeting dot on a specific spot you can gauge how uniform your heating efforts are going when you are heating large objects.I know the durn things have come down a lot in price since I bought mine back in the late 1990s.  I bought a Raytek pistol type that is good for temps from -25F to +999F and I paid over $300 for it.  I think the current model equivalent sells for around $190 or so.They have some less expensive ones that will read up to 600F and they would probably be OK for most preheating work. I bought it for various automotive work but it has also been used for preheating checks a few times.