If the clearance is correct on the stem to guide, you'll be OK. I originally went with no seals on the exhaust and got too much oil in the port, oxygen sensor, etc. Installed some viton seals and it cleaned up. No more smoke and less contamination of the O2 sensor. And I'm running methanol fuel which does not lube the upper end at all. Check with your head man and make sure he put in enough clearance.