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If your replacing your guides your machinest is the one the controls if everything is centered up .By the picture i dont see what your asking nothing is done but a little port and polish work nothing that controls were the valve guide sits? On alot of race heads they grind out all the valve guide that comes out of the head so that only tthe valve is restricting air . Im not sure if that helps any just ask your machinist he should be able to answer what ever your asking. He is the one putting the guides in.

 

Read the OP's question carefully and look at the picture he posted. He's refering to the valve guide boss area, the hump in the head directly in front of the valve guide itself. In the picture, it's been machined down.

OP, if done correctly, machining down the valve guide boss can improve flow

 

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My dad does all my head porting i dont know much about it man sorry i was just trying to help with what i do know.