tig weld cast cylinder head

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I'm going to weld this as an experiment either way,  but it would be nice to have a result that could pass a pressure test and perhaps works as a backup.   The head is cast iron and the corrosion/hole is in the #4 exhaust port.   I've welded cast before and I've filled plenty of holes before, but nothing quite like this.  Any thoughts or input is appreciated.
Reply:Well... If you'd follow the instructions in my O/A welding handbooks, you would use cast iron filler and preheat the whole thing red hot (obviously after removing everything not cast iron) to avoid stress cracks. Cooldown should be as slow as possible, packed in insulation/sand/ashes/back in the preheat oven.Preheating the whole thing is the best way to avoid stress cracks as it cools down after welding, but there are a few pretty obvious downsides to heating large engine parts red hot. If it was easy, everyone would do it.
Reply:Member castweld uses Eutectic and Cast Welding Tech torches with iron powder to weld up stuff like that.Do an advanced search for castweld threads to see some of his work.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Best bet from an engineering standpoint is using the "traditional" O/A method with CI filler as has been mentioned. Second choice would be the nickel based "spray welding" process. Bronze brazing will have limited service life due to different thermal COE vs the base material. Tig will be a disaster....don't bother.
Reply:I was/am concerned about using tig, but thought I'd give it a try as I feel this part needs to be replaced anyway.   I do like the idea of CI filler and O/A, but I'm not sure what my chance of success with that process is given my lack of experience with the technique.  I understand the CI rod can be hard to get and tricky to use.  Thanks everyone who has given input, it's greatly appretiated.   If I can't find a replacement, I will explore the options you've given me.
Reply:Cast iron welding rods & flux: http://www.cutlikeplasma.com/qs30/pr...ory=09-Welding SuppliesThey also have some demo videos, and there are many more if you spend some time searching youtube.A budget solution is to use old piston rings instead, they are made from high quality cast iron. If you are welding a piece of cast iron into the hole you would probably have enough piston rings to weld with in a scrapped lawnmower engine - although you probably want some practice first too.
Reply:GM marine? If it is its probably thin all over, check out closely. OA inside a port is going to heat the torch tip and popping occurs blowing away weld puddle. Bronze will erode in combustion chambers and exhaust ports. That leaves OA and cast iron filler. I use a lot of ni powder and have no luck inside a port because of heat radiated back into torch tip. Nickel tig or flux coated on a badly rusted casting will be nearly impossible to seal up. Sorry for the bad news, but if you do attempt post results good or bad. Good LuckPeterEquipment:2  old paws2  eyes (that don't look so good)1  bad back
Reply:Anyone tried this?http://www.davbroinc.com/products.htmTorchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:I hate to be a downer, But it looks like a GM 2.5/3.0 head. They were used in industrial applications so rounding up another one is neither hard nor expensive. From the look of the riser in the background it appears this was in the brine, I would look into how thick the block walls are before sinking a ton of dough into this project.Miller Big 40GMiller HF-251 D High FreqVictor OA Lincoln 135 MigMK 3A CobramaticBridgeport J HeadCronatron OxylanceRadnor ACAG TorchWeldcraft TIG Torches1 blown knee and two 5 Gallon pails away from being a hero.
Reply:Thanks for the input everyone.  As suspected,  it is a 3.0 gm.   I don't think the block is fantastic, however I did repair one external crack successfully I believe.  I have sourced a new head, however I do want to try the repair as an experiment.   If it's going to be scrap,  I may as well try.  I don't plan to run it, but assuming I am able to make what I believe is a satisfactory repair, I will have it pressure tested to see how it turns out.  I will update the thread when I have a chance to attempt the repair.  Thanks again everyone.
Reply:well I did attempt the repair using silicone bronze and it was going in very will with no detectable cracks.  Unfortunately, as I worked towards the back of the port, the wall thickness of the port on the floor is just too thin to be of any practical use.  Using 3/32 filler, the heat required to melt the filler was more than the paper thin port wall ( at the back ) could support.  Someone said these heads are easy to source, but I  haven't had that experience, here on the west coast for this particular pre-vortec 140 horse motor.  I would appreciate any leads anyone has.
Reply:Originally Posted by fulltrackwell I did attempt the repair using silicone bronze and it was going in very will with no detectable cracks.  Unfortunately, as I worked towards the back of the port, the wall thickness of the port on the floor is just too thin to be of any practical use.  Using 3/32 filler, the heat required to melt the filler was more than the paper thin port wall ( at the back ) could support.  Someone said these heads are easy to source, but I  haven't had that experience, here on the west coast for this particular pre-vortec 140 horse motor.  I would appreciate any leads anyone has.
Reply:Originally Posted by makoman1860The head has not changed in probably 50 years, at least as far as the marine useage is concerned. I wish we were still allowed to buy company property, I have probably scrapped 20 of them in the last year. Looks like the street price is around $500 for a new one. The local machine shops here in the Midwest usually have a few of them laying around, since its all freshwater here they usually are fine in that respect.
Reply:They have changed a bit.  The pre-91 140 horse heads have big ports and the 91 and later 'vortec' heads have smaller ports and the two most inner are not siamese.  I have found plenty of the vortec style online new, used etc, but the head I'm looking for seems to be on back-order from most of the AM suppliers.  I'm really thinking about switching this to the new style head/intake.  I'll have to cut the exhaust and modify it to match the location of the new style mercruiser riser.  Definitely not going to retro fit to OMC.
Reply:Ill keep my eye out for one here, shipping will probably kill it tho.Miller Big 40GMiller HF-251 D High FreqVictor OA Lincoln 135 MigMK 3A CobramaticBridgeport J HeadCronatron OxylanceRadnor ACAG TorchWeldcraft TIG Torches1 blown knee and two 5 Gallon pails away from being a hero.