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By 55ebird - 13 Years Ago
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I recently tore down a 1957 312 and noticed that both heads were cracked. One was cracked through an intake port and one was cracked through an exhaust port. In both cases the crack runs from the valve seat through the combustion chamber and onto the head surface as seen in the photo below. Can these heads be repaired and if so how? Also, are these cracks common? What causes them to crack? 
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By Daniel Jessup - 13 Years Ago
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The most common crack found on Y block heads is between the two center exhaust valves going toward the surface. Typically it is an overheating problem. I would assume that is why a majority of heads develop cracks such as these. I would advise against repairing a crack like that on any head, but I have heard of others talking some machine shop into repairing it... I have seen where a hole was drilled at each end of the hairline, rods inserted, and then the crack was simply welded up. I guess it depends on how hard up you are. I would search for another set if it was me.
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By Riz - 13 Years Ago
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The money you spend at the machine shop trying to get repaired would be better spent on a new set. I have known of guys trying to repair cracked heads and they all failed after a time.
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By PF Arcand - 13 Years Ago
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Many machine shops are not setup or necessarily qualified to do competant cast iron welding. It needs to be done by someone that is conversant with the procedure & equipped to do it properly. Unfortunatley there are not many such people & doing it properly is usually expensive, due to the labour & material involved. Unless you can't find replacements & are willing to pay the price, it probably isn't the route to go.
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By DANIEL TINDER - 13 Years Ago
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While experienced cast iron welders can be found (rural workman used to salvaging old farm equipment, in my case) few will likely want to properly dress & polish their work (chamber uniformity?). Another consideration not mentioned: Are these heads posted? If not, then gambling on a successful repair may be a sucker's game.
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By mctim64 - 13 Years Ago
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That crack show is easy to repair, it's the cost of the labor to do it. Another head may be cheeper. I have done it on many heads with great success. BTW, that is the most common crack I've seen in "G" heads, just like that! 
Cut and install a seat, then pressure test. Done!
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By lowrider - 13 Years Ago
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FWIW saw a single "G" head on Epay today. Starting bid was 99.99, no bids yet with a couple days to go item #370717733853
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By jhtdon - 13 Years Ago
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2 Years ago I purchased new heads from Carpenter, $99 each. They are New 62 vintage truck heads and they really woke up my 50 ford with 292 and McCulloch. Both heads were cracked, went to the scrap dealer.
Cheers, Don
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