Advanced timing will not cause it. Retarded timing will.What would likely cause that? Overheating the valve from: mixture too lean , RPM too high, timing too advanced...?
Tulip valve is caused by too much spring pressure, for the temps.
Exh is always the smaller one AFaIK. Exhaust gas has a higher differential pressure across the valve so that gas move faster and doesn't need as big a hole. Also the smaller the valve the easier it is to cool.Newby question: which is which? Is the biggun Ex or In?
Exh is always the smaller one AFaIK. Exhaust gas has a higher differential pressure across the valve so that gas move faster and doesn't need as big a hole. Also the smaller the valve the easier it is to cool.
Okay but for the record this valve ain't "tuliped" it's just some sort effect from the flash. If you look in there the face is as flat as the Black Rock Desert (which is flatter than a pancake)
I'm always hearing people claim that a quick peek with a borescope will tell you all you need to know. I disagree.
...I'm guessing you make a lot of money pulling cylinders...
Exh is always the smaller one AFaIK. Exhaust gas has a higher differential pressure across the valve so that gas move faster and doesn't need as big a hole. Also the smaller the valve the easier it is to cool.
And the gas's temperature reduces its viscosity so it flows easier. I think that the much higher speed of sound in hot gases might have something to do with it, too. No shock waves to deal with.
Dan
41/80 exhaust valve leak. Pulled the cylinder and this is what it looks like looking right down the barrel.
Still think a borescope or a $35 dental camera is gonna tell you somethign you don't already know?
I have looked at the picture posted and can't see where that valve is failing...
Which was my original point, the valve was failing yet there are no visible signs that could be detected by borescope inspection. In your case, are you saying the compression test was satisfactory but the valve was visibly damaged?
No, when we pulled it in and checked compression on that cylinder was 0.
So you are saying the problem with the valve was in the stem (wobbling) or something that can't be seen on the face? If that is the case, I get it now.
Getting a 0 on a compression test is VERY hard to do....Unless the entire piston or both vavles are missing..
Getting a 0 on a compression test is VERY hard to do....Unless the entire piston or both valves are missing..
O-360, 550 hrs SMOH, no idea how many total hours are on the cylinder. I took it to the machinist and a quick test shows both valves leaking, about 50% on exhaust. He also noted what looks to likely be a crack between lower plug and exhaust valve. With the price of individual parts and labor involved it's pretty much impossible to beat $1187 for a brand new Lycoming cylinder which comes with everything including new piston so that's my recommendation.
My point is that, as bad off as this thing is, you wouldn't really know it just to look at it, especially in-situ with a $150 320x280 video-scope. Even the suspected crack, you'd have to blast and dye check to be certain. I'm always hearing people claim that a quick peek with a borescope will tell you all you need to know. I disagree.