you don't necessarily have to replace the head bolts, but they do need to be measured by a machine shop. these are torque to yeild bolts and "streach" is engineered into them. You can find the specs in some chiltons manuals or some machine shops will know them, but there is a maximum length that they can have steached to before they must be discarded. I recomend replacing them with the generic ones on fcpgroton.com, as they are way cheaper than volvo parts and have served me just as well...I believe volvo parts were $10.50 each!!! and there are 10 if i recall correctly. make sure that you torque them properly and in the correct sequence. do not use washers as that may throw off the streach needed in the torque to yeild process...good luck.