The Cessna 120-140 Association Forum

Back-story for context: My C-85 engine continually drains oil from the carburetor inlet during operation. Blows back on the firewall and down the belly. The rumored cause of this is either: (A) worn inlet valve guides, or (B) running a rocker arm on the inlet valve that does not have the plugged oil drilling. (I'm hoping for (B).)

I purchased a set of plugged rocker arms. Sent them off to Lycon to be overhauled. Now I intend to install them in the hopes that this addresses the oil leak. Continental specs are to check valve clearance with the lifter deflated. Which is the source of my question:

How do I deflate the lifter without removing it from the engine? What's the cheat-code? Thanks in advance!
-dave sprinkle

Turn the engine to where the valve in question is fully open. Go have a beer. Works best with warm engine oil (and cold beer.)

6643 wrote: ↑Wed May 28, 2025 2:15 pm Turn the engine to where the valve in question is fully open. Go have a beer. Works best with warm engine oil (and cold beer.)

John, great advice! Thank you!

I am sure you have fixed it by now but if you ever need to do it again do the following: Remove rocker arm, remove push rod. Thread some .040 safety wire through the push rod until it protrudes a little way out the end. Insert rod back into the engine while holding the wire in place and push until it bleeds down. The safety wire unseats the ball valve inside the lifter and allows the oil to drain out. I've done this several times on other engines.

John,

Tried this tonight. After turning the prop to close the valve there was a gap between rocker and valve (yay!), but then the lifter reinflated, taking up the gap. Normal? Just check the gap quickly?

It may re-extend on its own, but it shouldn't be full of oil. That takes oil pressure. If you push on the pushrod end of the rocker with your thumb you should be able to push it back down again.