The Cessna 120-140 Association Forum

We've had our '47 C120 (C-90-12F) for about 8 months, and it's running great. We are, however, noticing some oil coating and puddling on the bottom of the cowl, and it's clearly traceable to the pushrod tube rubber seals/clamps. I understand this is a known issue with Continental engines.

The leak, at the moment, isn't severe (it did soak the entire carburator, airbox, and surrounding accesories with a pretty good coating). All pushrods seem to be leaking pretty much at the same rate.

Two Questions:

- How much oil leaking is "too much"? Seems manageable right now.
- I see the REAL conversion kit is about $480 from Aircraft Spruce. How much labor is typically required to install?

Is this an upgrade that you would recommend? (anything to look out for, after the change?). The aircraft is going in for annual in November, so that may be a convenient time for the upgrade?

Pretty common, down side is cylinder needs to get backed off 1-2" to install new ones. we installed ours new 500hrs ago (during Major) smeared a little Hylomar to ease install and help seal also used your style clamps and no leaks yet. So real question how far do you want to go ? TTSMO? using oil? Good Compression? Don't make a mountain from a mole hill but do what it needs and fly safely. Just my thoughts.

I've done the REAL kit on two cylinders. The first one took me a little while but the second one was done in a couple hours easy. The instructions are good and theres some decent youtube videos to help too.

Cylinder does NOT have to be removed to do the REAL kit.

6898 wrote: ↑Thu Sep 19, 2024 2:06 pm Pretty common, down side is cylinder needs to get backed off 1-2" to install new ones. we installed ours new 500hrs ago (during Major) smeared a little Hylomar to ease install and help seal also used your style clamps and no leaks yet. So real question how far do you want to go ? TTSMO? using oil? Good Compression? Don't make a mountain from a mole hill but do what it needs and fly safely. Just my thoughts.

Thanks Jeff! To your question ... the airplane is really not using much oil (1 qt per 8 hours, our records show). Is that about average?

tonycondon wrote: ↑Thu Sep 19, 2024 9:44 pm I've done the REAL kit on two cylinders. The first one took me a little while but the second one was done in a couple hours easy. The instructions are good and theres some decent youtube videos to help too.

Cylinder does NOT have to be removed to do the REAL kit.

That's good to know! If we do it, we're leaning toward having them installed during annual, in November.

vindio wrote: ↑Sun Sep 22, 2024 5:14 pm

6898 wrote: ↑Thu Sep 19, 2024 2:06 pm Pretty common, down side is cylinder needs to get backed off 1-2" to install new ones. we installed ours new 500hrs ago (during Major) smeared a little Hylomar to ease install and help seal also used your style clamps and no leaks yet. So real question how far do you want to go ? TTSMO? using oil? Good Compression? Don't make a mountain from a mole hill but do what it needs and fly safely. Just my thoughts.

Thanks Jeff! To your question ... the airplane is really not using much oil (1 qt per 8 hours, our records show). Is that about average?

You're in the "ballpark" on oil usage. About 3-4 hours per quart and I'd be concerned. I get 10 hours per quart, I'm happy,
The best I've seen is 25 hours per quart, .......for an old air-cooled engine with "old" clearances......that's probably a little too good.

Same situation and I’ve had the same thought. Great minds, huh?

If you decide to do the conversion, let us know how it goes!