Im ready to start building the head for my 250 so I will be needing valve seals.

I have tried researching and it seems the consensus is to use Viton but my question is which ones and umbrella or locking. I have machined bosses. As well do they work on the intakes as well as exhaust or would I need different ones for the exhaust.

I have had good luck using PC stem mounted seals.

Be sure you have adequate seal-to-retainer clearance for the cam being used and adjust guide height accordingly.