Strange air leak in ignition cavity

[d2w]

This may be a case of "If it hurts, don't do it!"

I have a '06 EC300. I've modified the ignition cover so that the drain (fill ) hole on the bottom is plugged and there's a hose nipple on the top. A hose is connected from the nipple and is routed up in behind the rads.

As a test, I blew into the hose and I could hear air hissing out somewhere in the vacinity of the spark plug, head, or exhaust port. Would you expect that? I would have thought the ignition cavity would be sealed off from the engine crankcase. Or perhaps the seal is designed to only work with the crank at a higher pressure than the ignition cavity? But doesn't the crank cavity pressure go negative during the intake stroke?

I need to more precisely identify where/if I'm hearing a leak. But I sure would appreciate it if someone could say "Ya, that's normal".

And I'm experiencing no engine problems, or oil in the ignition cavity, etc.

Again, perhaps I simply shouldn't be blowing into the ignition cavity.

Thanks

Dale