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Some of the circle track guys around here run their engines with no valve seals. I've always understood that even small amounts of oil in the chamber will dampen power output. Anyone have any dyno or personal experiance with running engines with and without valve seals?
My biggest worry in a boat would be detonation. Ever heard an old car pinging itself to death as it smokes it's way up the grade out of Indio??
The outboard guys will tell you it is no problem :p .
When I diass my engine it had no seals on the exh valves. Not sure exactly why it was like this. Speculation would be that the exh valve gets ALOT hotter and the extra oil on the stem keeps it from seizing in the guide while making more heat when racing smile_sp . When I put it back together I placed seals on all guides (along w/ new exh valves).
Running the exhaust with no seals is not uncommon on race or high output engines. The extra oil will make sure the valve runs well lubed and cool. On my turbocharged engine I run without exhaust seals and "umbrella" seals on the intake. The exhaust and boost pressure seem to control consumption. I tried no exhaust seals on my naturally asperated engine and found the exhaust were wet with oil, since went back to seals on all valves on that engine.
I leave the seals off on a race engine.
Most others I leave the seal on but take the spring off of the seal. Trying to help keep crankcase pressure down as much as possible.
Boost can go past the seal during overlap. Will go past a valve stem with no seal for sure.