Re: Cylinder Head Cracking

>> Hi, >> >> I was hopeful that someone might be able to give me a different insight >> into a problem that occurs with my dads celica.

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>Also, you should be using new head bolts every time the head is removed as >they are designed to stretch when tightened. If you are re-using the same >bolts, they may not be supplying correct torque.

I'm missing something here Ray. If the head bolts are designed to stretch when tightened, wouldn't they stretch over time with heating and cooling cycles? That would result in less than the designed compression of the head gasket and leaking or blown head gaskets after a few years.

Also I would think that reusing the head bolts would result in warped heads due to the above uneven compression. The effect would be the same as applying the correct torque on only some of the bolts. But I don't see how it could cause cracks through an exhaust valve seat.

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Retired VIP
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Toyota refers to the stretch-to-torque head bolts as plastic region head bolts. Tightening them to the specified torque also stretches the bolt permanently. I don't know why they don't stretch more over time with heating and cooling cycles, and I don't know what advantage there is over conventional head bolts. I don't really see how re-using old bolts would cause cracks through an exhaust valve seat, but just to cover the bases, I thought I'd mention them.

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Ray O

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