S

sneedrv-6

Well Known Member
Did a cold and hot compression check today and I can hear air escaping from the exhaust valve. I am wondering if it is worth pulling the jug(s) and re-lapping (inspecting) the valves. A guy on the field says that if you have an exhaust leak you should fix the issue, I have also been told as long as it passes compression test to keep flying.

cold
1 71-80
2 68-80
3 66-80
5 72-80

hot
1 74-80
2 70-80
3 68-80
4 76-80

Thanks a lot,

Jason

rv-6 o-360 (airflow fuel injected) 1,500 hrs on engine.
 
1. Fly for an hour, see if it fixes itself.
2. Stake the valve (remove rocker arm and hit the valve with a mallet). Seldom works but easy to try.
3. I know of some who have lapped in place, working thru a spark plug hole.

You might try to get a boroscope picture to make sure the valve isn't burned.
If the valve guide is worn excessively the cylinder has to come off.
Have you done the wobble test? Perhaps the valve is sticking slightly open. If the answer is no i'd do this first, and on all cylinders.
 
Jason,

53 views and not one reply, that must be a record!

OK, lets be pragmatic about things here.

1. Do you have an engine monitor and can you send me the data file. This is most important.

2. Do you have one of these digital boroscopes (sub $100 on ebay if you get the right one) and can you do some thorough image taking of the valve and even a video of it opening and closing. Be very careful doing this, the piston might bite the camera and then you will be pulling a cylinder.

3. Which cylinder? Nothing in your list of leak downs is noteworthy and to be honest I am not surprised.

4. Did you go for a good hard run, full bore and come back hot and do it again after those two, if so what then? Pull the prop around a few times then do another test.

Let me know how you go, and email me the data file and pic's.
 
If an exhaust valve is leaking, it will eventually burn... guaranteed.

Sometimes re-lapping the valve will fix it as a stop-gap measure if caught early enough, but a trip to the cylinder shop will get it fixed properly. Does it pass the wobble test? 1500 hours really is a pretty decent amount of service life to have gotten before the first valve issues start popping up on any Lyc.
 
As others have said - the recorded numbers, on their face, aren't alarming.

A recent wobble test and a look at the valve with a borescope is important. You don't want the valve "clunking" back into place as it closes (you'll stand a good chance of a piece of the valve breaking off, you'll be looking for a place to land, and the cost of the repair will suddenly increase).

Dan
 
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