Lycoming 390 Rocker Shaft Clearance Cyl 4

[Micke]

I am a new owner of an RV14A. 330h on the engine and a sticky valve. There seems to be very little clearance for angle valve cyl 4 exhaust rocker valve shaft. See picture. Would this clearance typically work for pushing out the shaft part of the way to remove the rocker? If not, any suggestiojs what I can do.

Mike

 

[dmattmul]

I am a new owner of an RV14A. 330h on the engine and a sticky valve. There seems to be very little clearance for angle valve cyl 4 exhaust rocker valve shaft. See picture. Would this clearance typically work for pushing out the shaft part of the way to remove the rocker? If not, any suggestiojs what I can do.

Mike

Join the crowd, what cylinder was this? How did you pick up a sticky valve? Any chance you can post your .csv files last 5 flight? Hard to see what you are describing. Pictures of valve guides would be better.

 

[Micke]

Join the crowd, what cylinder was this? How did you pick up a sticky valve? Any chance you can post your .csv files last 5 flight? Hard to see what you are describing. Pictures of valve guides would be better.

Cyl no 4. Morning sickness three times. Lost EGT on cyl 4 for 55 seconds last time. Plan is to ream the valve guide. I now saw another post by a member with same issue and he was going to fabricate a hatch in the baffling so the valve shaft can poke through.

 

[dmattmul]

Cyl no 4. Morning sickness three times. Lost EGT on cyl 4 for 55 seconds last time. Plan is to ream the valve guide. I now saw another post by a member with same issue and he was going to fabricate a hatch in the baffling so the valve shaft can poke through.

Call me naive but I am "hoping" my IO390 will talk to me before this occurs. After every flight I review my .CSV file. Waiting to bend a valve shaft would not be a good day for me. 700 hrs so far ok.

 

[Phil Sprang]

I've been told that the #4 rocker arm shaft can't be removed without removing the baffling. I'm still building but it was suggested to me to make provisions in the baffling to be able to remove the rocker shaft.

This is what I did. These are in process pics but you'll get the idea. I'm sure a simpler solution is available.

 

[DanH]

Yeah, the baffle tin has to come apart, or you'll need the hatch. Here you can see I've drilled three rivets, removed the tin over the valve cover, and pushed the rear baffle wall rearward by shoving a screwdriver behind it.

This was a routine wobble check at 1200+ hours. All exhaust clearances were in the middle of the range. I like the higher coking temperature of a part-synthetic.

 

[RV8Squaz]

Yup. Your choices are:

1. Remove the baffle.
2. Make a hatch in the baffle.
3. Drill out rivets like DH did. Replace with screws and nuts. I just went through this on my Extra. Fortunately the previous owner had made whole sections removable with screws and nuts.

Jerry

 

[Micke]

Thank you everyone. I was thinking that I could use a step drill to make a small hole and push out the shaft. Then plug it as shown in the Kitplane article https://www.kitplanes.com/plug-that-hole/. See picture.

Mike

 

[DanH]

Thank you everyone. I was thinking that I could use a step drill to make a small hole and push out the shaft. Then plug it as shown in the Kitplane article

If I actually do another check prior to overhaul, I'm thinking a hole, then just slap on a piece of soft aluminum duct tape to close it.

 

[Reflex]

I took a look at the issue last night on my -14. At 105 hours, I have yet to do the wobble test and haven't had any symptoms. That being said, as I near the time for condition inspection, my plan is to do the check(s). The many comments on this forum pointing to problems with the #2 exhaust valve make me want to get in front of the potential problem. I might as well check them all.

My question is, what about the clearance on cylinder #3? Does the hole/vent for the oil cooler duct provide enough clearance to remove the rocker arm shaft?

The port for the shaft seems pretty low for that to work, however the shaft appears to come out at an angle that may be enough for the the oil ducting hole to allow clearance.

By the way Phil, your solution looks great!

Fred

 

[DanH]

My question is, what about the clearance on cylinder #3? Does the hole/vent for the oil cooler duct provide enough clearance to remove the rocker arm shaft?

The #3 exhaust rocker shaft is on the forward side of the cylinder. Points up over cyl #1 when pulled.

 

[Reflex]

The #3 exhaust rocker shaft is on the forward side of the cylinder. Points up over cyl #1 when pulled.

Thanks Dan. I wondered about that and figured that was probably the case. However, when I saw the "hatch" on the back side of #3, I thought that I might need to have access to what was under it.

Thanks again,

Fred

 

[Micke]

Thanks Dan. I wondered about that and figured that was probably the case. However, when I saw the "hatch" on the back side of #3, I thought that I might need to have access to what was under it.

Thanks again,

Fred

I made a small hole to push out the shaft. Below link to my youtube video showing the process including reaming the exhaust valve. I had no prior experience in this area but it is very doable. Study vansairforce posts, kitplane articles, youtube videos. Follow the steps in the applicable engine maintenance manual. Pay atttention to parts like gaskets and washers that should be replaced. The parts numbers in the parts manual can be used when ordering parts from Spruce.

Mike