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Not specific to this, but have you tried attacking it with a die grinder and grinding down to the good stuff before welding? (I have no other thoughts right off)
 

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I assume you are trying to weld to cast aluminum, but what are you welding with ?
or am I out in left field catching grounders
 

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Have you tried baking the head for awhile in the oven to drive out any oil etc that may be in the metal? Its kind of a long shot at this point. :(
 

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Bet these guys could do it

When I was in Madagascar last month, I had the opportunity to visit an Aluminum casting "factory"





The workers there were melting down recycled aluminum from car parts and scrap aluminum from all sorts of things, melting it over charcoal fired adobe brick furnaces, and sand casting it into cookingwear and art objects to sell. It was freaking Amazing!





As well as dirty, dangerous and probably health endangering





But those guys could cast aluminum like nobodys business.





My point is, if they could do it under those horendous conditions and with those tools, you probably can too.




Maybe try cleaning the metal surface where you want it to stick, sand fill the areas where you don't want it, melt some aluminum and pour it into the spot you want to fill, then machine it to shape once it cools.

Note: the handles on the pot lids were cast separately, cooled and put in place when they did the final pour. The finished product became one piece.
 

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I'll try some brazing alloy and flux before giving up... what's upsetting is that I've seen 450 heads and I think 350 heads modified this way, but no one wants to give up their secrets :D
Two problems you might encounter is that just as solder melts at a far lower temperature then the copper you are trying to attach it to, the temperature of aluminum brazing materials liquify at a much lower temperature then the cast aluminum you are trying to build up. (in the realm of 500 to 750 degrees lower) You also can't build it up in successive layers, because it all turns to liquid each time you melt it. Exhaust ports tend to be extremely hot right above the valves and are constantly bombarded by the rapid flow of hot gases.

You are gong to need to inspect it after some heavy use to see if there is anything left of the soft material you have added, or if it has all blown out the exhaust pipe.

Best luck with the repair.
 

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Looks like my casting setup. :D
Post pictures, would be very :cool:

… was interesting to see them still adding solid chunks of scrap aluminum to the crucible, right up until the time they started the pour.
lol occurred to me at the time it might not be a good place to park your car in front of and then go for a walk.
 

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Car guys use what they call tounge depressors on some big blocks that have to big of a port. Its a steel ring with a tounge that becomes the floor of the port it gets sandwiched in between the head and header.
 

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I'm not a welding expert, but I do get by ok with my TIG. The following is what I've read and seen. I have not welded on cast aluminum personally so take it for what it's worth.

The biggest problem welding aluminum and in particular cast aluminum is that it is hard to get clean. No matter how clean you think it is because of the pores in cast aluminum and envirnoment, it is dirty.

That leads to your problem. A syncrowave lacks the ability to adjust the cleaning action of the AC current.

This is one situation where I don't think your good ol transistor welder will not do as well as the newer more adjustable inverter units. You can adjust the % + % - to deal with the impurities that invariably bubble up as you try to form a puddle.

I'll see if I can dig up some videos.
 

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welp, I got some of the brazing alloy to stick, seemed to wet out fairly well too, worth experimenting with anyway, however, it became a real challenge (failure) to be able to build up in one area without melting the whole lot, I think that has a lot to do with the aluminum head evening out heat so quick that once a tiny area is of melt temperature, the whole rest of the area is too. gave me an idea though, that maybe I should insert an aluminum plug in the valve seat cutout and at the exhaust port, and heat the thing up and stick rods down the valve guide hole until it builds enough on the floor, then wait for it to cool, pull the plugs and grind away
 

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welp, I got some of the brazing alloy to stick, seemed to wet out fairly well too, worth experimenting with anyway, however, it became a real challenge (failure) to be able to build up in one area without melting the whole lot, I think that has a lot to do with the aluminum head evening out heat so quick that once a tiny area is of melt temperature, the whole rest of the area is too. gave me an idea though, that maybe I should insert an aluminum plug in the valve seat cutout and at the exhaust port, and heat the thing up and stick rods down the valve guide hole until it builds enough on the floor, then wait for it to cool, pull the plugs and grind away
does it sound like aluminum oxides that have a higher melting point than the base aluminum that you're having difficulty melting through?

Ever try the Helium/Argon trick. Gives you extra heat you need to melt the area quickly and weld.
 
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