I'm dropping in an 03' 5.4L 2V with 109,000 on it with excellent compression and am going to change out the valve stem seals first while still on the pallet. Who in your opinion makes the best VS seals, longest lasting? I see the FelPro brand says they're "improved design". What's the best for long term use?

Thanks.

 

I would just like to know who make the longest lasting valve stem seals out there? Doesn't anybody know????????? I know the better ones are made of Viton but would like some experienced answers.