I have a 1970 360 which I am freshening up to put in a Javelin. I took the 291C heads to the machine shop yesterday for a quick valve job. The machinist called today and said both heads were cracked. I retreived the heads today and he showed me the cracks which are visible on the rear of the heads where the thick part of the head runs onto the "shelf". There was no obvious sign that the engine had been overheated but it is a used engine and I don't know the history. The machinist says they can't be fixed. He also said that he doesn't see that many AMC heads because they don't do much Jeep work, but he has seen a disproportionate share of cracked AMC heads. He warned me about this when I dropped them off. Joe Fulton Salinas, CA