Originally Posted by 6damian6
I spoke to a machinist and he said that if i want new valve guides he will also have to regrind the valve seats, is that a must when installing guides?
Yes this is a must. When you change the guides the angle the valve face to the seat changes. The valve wont seal against the seat unless the guides are installed and then the seats are cut concentic with the valve guide. Its a good Idea to replace the stock guides when doing head work with the bronze magnisium guides. Stockers are steel. Alot of guys skimp on this step because its very time consuming, but should be done on every perfomance head.