0-320 sanity check

[Timbeck2]

It was discovered at the last annual that my engine didn't have thrust buttons installed on the rocker shafts. I ordered the parts and installed them then discovered that the rocker cover won't fit over the thrust buttons. After a little research I discovered that on my 1970 era engine, they used longer rocker shafts and didn't use the thrust buttons. My choices are: A leave it as is, B install shorter rocker shafts C install different rocker covers.

Anyone else have this issue...if it is an issue?

 

[bnt83]

Are you sure the rocker covers are the same across all years?

 

[Timbeck2]

Don't understand the relevance of the question. The rocker cover is the correct part number for my engine.

 

[bnt83]

Don't understand the relevance of the question. The rocker cover is the correct part number for my engine.

If the rocker cover was wider or narrower that would determine what shafts fit.

I can look all day long at the E2D parts manual released in 2011 and see stuff that has changed since my E2D was assembled in 1967.

 

[Domenick]

I can't help with an opinion. But, I did find this from 2018-08 at: https://www.shortwingpipers.org/forum/showthread.php?12399-Missing-rocker-shaft-thrust-buttons

Post #6: Teflon buttons require a shorter rocker shaft, you cannot use them with the longer shafts. Also, if you don't mind using aftermarket rocker covers, Aircraft Specialties in Tulsa have them for around $20 each. I see on ebay guys are asking way over that for used ones.....that say Lycoming....Seems like a no brainer to replace rusted or worn rocker covers at that price. (SL61247 $20.95) they look cad plated.

http://www.aircraftspecialties.aero/search.php?search_query=rocker covers&section=product

 

[Timbeck2]

Yep, read that as well prior to posting this here. Went to the Aircraft Specialties site and looked at Lycoming 61247 part number and the Millenial rocker covers (the SL61247) and didn't see much difference in the two other than the Millinial looks more vertical than the Lycoming. I think I'm going to leave it as is since its been flying like that since 1970 and keep an eye on the rocker covers for wear through.

 

[Dan Thomas]

For the guys flying Lycs in E-AB, there are very nice aluminum rocker covers available that have an O-ring instead of a gasket. No more leaks from shrunken gaskets.
http://sdsefi.com/sdsaero.htm

Scroll down the page a little.

 

[Timbeck2]

Thanks Dan, those are cool but not $120 per cover cool.

 

[Stewartb]

Brand new from Lycoming's exp Thunderbolt shop. Conventional covers, silicone gaskets.

To the O-320 question? If it ain't broke, don't fix it.

 

[Dana]

...I think I'm going to leave it as is since its been flying like that since 1970 and keep an eye on the rocker covers for wear through.

I came to the same conclusion about the missing buttons on my O-290.

 

[Dan Thomas]

Thanks Dan, those are cool but not $120 per cover cool.

You're old like me. It's young guys with too much money that buy expensive cool stuff. But "expensive" is relative. For some commercial operators looking to stop having to spend expensive shop time fooling with leaking rocker cover gaskets every 300 hours or so, SDS covers would save money. (If those covers were PMA'd, which they're not.) Even the silicone gaskets you can get to replace the original cork gaskets will leak if they're overtightened, which a lot of them get. The big problem is that the screws have to be left at a low torque setting to avoid extruding the gasket,* and now they'll tend to loosen as the engine vibrates. SDS's covers clamp down tight against the head, metal-to-metal, and the screws can be taken to their recommended torque and they'll stay there.

*The gasket has a narrow margin around the screw hole. That part can extrude into the rocker cavity and oil then gets into the screw hole and wicks out around the screw.

In the old days those screw heads were drilled for lockwire. More work.

I spent a bunch of years rebuilding air and hydraulic brake components, vacuum pumps and air compressors, for heavy trucks and machinery. In the 1970s there was a big shift away from gaskets to O-rings for sealing air and fluids. Gaskets are expensive to make and they deteriorate. Pulling something apart for maintenance ruins it. Many gasket compounds will leak air or other gases right through the gasket. O-rings, especially in the last 30 years, have become available in a wide variety of polymers to resist heat or cold or just about any chemical, and they made stuff last a lot longer and leak a lot less. I find it rather disgusting that aviation is still using gaskets in so many places where an O-ring would work far better. It's falling to aftermarket people to instigate it. Look at what Ly-Con is doing to crankcase half mating faces to eliminate the ubiquitous case seam leaks:

https://www.lycon.com/improve.html

 

[GLDP]

I had all my cylinders off last year on my O-320-E2D and I also found no thrust buttons. At the advice of my AME we ordered them but like you we found they don’t fit and I left them off. The only thing the thrust buttons seem to do is prevent wear on the rocker cover but after 2000hrs the covers only had minor wear so I assume it will be a long time before they wear through.

 

[mondtster]

Anyone else have this issue...if it is an issue?

I ran across this "issue" about a month ago on an experimental that had the engine overhauled in the late '80s. I'm not sure when the change was made but there are two different lengths of rocker shafts. One for use with the buttons and one for use without. The reason the buttons came about was to keep the shafts from wearing a hole in the rocker cover.

Since the aircraft/engine I was working on was on an experimental the owner just put the long rocker shafts in a lathe and turned them down until they matched the dimensions of the short rocker shafts. Then he used the buttons and everything is good.