One needs to be careful with aluminum heads. The casting is not very thick in the valve guide area and can be fractured with too much hammering. The head needs to be heated and the guides pressed or pulled out. Same is true for reinstalling new ones. The interference fit is necessary to keep the guides in place while the engine is operating over a normal or occasionally, abnormal range of temperature.

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.