what would cause a valve guide to break / crack? i got a head but 1 of the valve guides is broke in half and another is cracked in 3 places... i'm going to replace them but wtf could cause this? shipping? i heard they can only break by a bent valve, and if whoever had this head before if a valve was bent, that wouldent have any effect on the condition of the head would it?

 

It has been my experience that bent valves can often lead to damaged valve guides. It would be pretty tough to damage valve guides during shipping, given their position in the head.

 

on my motor bent valves caused broken guides

 

would that affect any other part of the head other than the broken valve guides?

 

In extreme cases, the valve seats can also be damaged.