OK I am removing the head on my XJ with 3000k plus well cared for miles on it. I have low compression cyl 1and2 no visible crack or evidence of leak engine is clean inside no sludge or milk. My question, is it advisable to use this head or replace it, my thought is if it was going to crack it would have already done it. Any pointers for getting invisible manifold bolts out????? thanks in advance. CURT