Cast head

admin

I have a flat head that had a lengthy crack on the top of it.. Fortunately it is only on the water jacket, not tied into any internal supports. My big problem is that I cannot preheat it to a good temperature or post heat it due to it's size.  I tried to tig in some MG 200 filler, then I tried to stick MG 250.. Both of which would crack after welding and even pinging.. So I was thinking that brazing would be an option.. Has anyone ever tried this with a flat head?  What other options do I have?  I do have thermal spray.. but, again, I cannot keep the head to a workable temperature and I'm sure it will crack even worse. Attached ImagesCommon sense in an uncommon degree is what the world calls wisdom.
Reply:get the outside fire pit going and hang it over that...LOL...
Reply:Seems like oxy-fuel would be the answer,welding or brazing. Makoman would be a good one to ask.maniak
Reply:I have no help for you on that except maybe Castweld might be on here and see this thread.
Reply:Your idea of braze welding may be the answer.
Reply:Originally Posted by pulserYour idea of braze welding may be the answer.
Reply:The flat head on my 52 Ford tractor was brazed more than twenty years ago and still works fine. It was a long crack like yours but not as open, if that makes sense. The bead itself is very large. LOcal welder did the job.
Reply:Unfortunately I had to open it up that far because it was spider webbing to the sides a little.  So that settles it.. Brazing I will go!  Nothing a little paint cant hide.Common sense in an uncommon degree is what the world calls wisdom.
Reply:Braze or powder spray will require 650 minimum pre/post heat. That crack. in the middle of the head, on a flat surface will be a problem. It had cracks leading off of main crack? May be already welded and failed again. Don't be sacred of heating, can be done on old bbq pit over charcoal, use temp sticks to check heat. I wouldn't attempt w/o heat. PM me if needed.Peter
Reply:So I preheated the piece to over 700 degree's.   I tried to use spray transfer (stoody # 22) and it was a big back fire.. I was having no problem building it up around the edges, expect for one corner where it would pull away and almost ball up. I figured I was getting too much heat because of my position.  So I ground  it out and moved on without any problem...  Very soon after I was finished, I saw cracking around my welds where my input heat wasn't that much, so I figured it was some funky casting... After grinding out a bunch of places, I broke out the brazing rod.  With a little finesse, I managed to bridge the gaps, covered it up with a plate, card board and a blanket, it managed to stay together without another hick up.  So.... My big question is: What causes things to crack along side the weld when your parent metal is at a constant 700 + degrees? I know where I put more and less heat in the areas, and it is not consistent to where you would think. Like where I put a ton of heat... No problem.. Then again, another spot, cracking.. and Vise Versa..  Also, I had the head sitting on tubes that allowed a torch to keep heat to the project from underneath while I fiddled on top.  The cracking seemed almost random.    On another note.. To preheat something of this size with rosebuds, it cost alot of gas. I'm charging him 2 hours for that repair.. What would you charge?   A fire pit would have been great, but that was not an option since I am in a business complex and I think the land lords would have a bit of a guff with me starting a fire that big in the parking lot.Common sense in an uncommon degree is what the world calls wisdom.
Reply:You need a BIG box of Vermiculite to put the head in after welding..Cools real sssllllooooowwwwwwwww and stops the cooldown cracking.....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:Cracked before cool down? That is most often the case, most people think it cracks long into the cool down. The cracks occur almost immediatly. Arc (stick, mig, tig) is in the several thousand degree range. Some articles claim around 15000 degrees, others claim much higher. I have no way of testing so- hell I don't know! But what I do know is the arc creates too much temperature differential. If you grind a "good" arc weld on cast iron it will have cracks in boundary layer. Laying a bead on top of casting and peening the hell out of it will sometimes close (hammer shut) the cracks enough to seal it. 99ni works best. I have had equal succcess (and failure) on outside water jacket arc welds with preheat or welded cold. When welding a open gap as you had w/arc I have had mostly failures.  OA way to go.To make a decision on how to weld (jobs that are not worth much)  I will light up the tig and look to see if a puddle will form, puddle= tig or stick. Metal "pulls away" and balls up= gas weld. My theory is that higher carbon content is problem in some castings, or areas of a casting.I charge min of $80 for oven weld, but I make money pressure testing, surfacing, ect. If I get it done first try, total time for job is low. But sometimes it takes a second or third try. I like a carbon rich fire to heat- and yes I have a theory about that also. ( no propane)Peter