ArtVandelay Posted April 17, 2020 Report Posted April 17, 2020 IIRC, Savvy supposedly scans for a saw tooth pattern in the EGTs which is the telltale sign of pending valve failure. I would send a note to Mike Busch, they might be interested in looking at your data, personally I don’t see anything wrong till you pull the power back before EGT goes wild. 1 Quote
aviatoreb Posted April 17, 2020 Report Posted April 17, 2020 Well - good to be on the ground sending pictures of a bad valve! I can understand the hesitation to make an off field landing, or a diverted landing, during a pandemic, more so than usual. Glad you resisted! 1 Quote
LANCECASPER Posted May 29, 2020 Report Posted May 29, 2020 On 3/29/2020 at 9:11 PM, Phil EF said: Valves don’t know whose name is on the data plate. Of course not, I was just pointing out which engine the Bravo had, so people weren't confused. 2 Quote
Awful_Charlie Posted May 30, 2020 Report Posted May 30, 2020 On 3/30/2020 at 4:11 AM, Phil EF said: Valves don’t know whose name is on the data plate. Indeed, but all valves are not the same. IIRC Lycoming exhaust valves use the sodium pellet to get more heat away from the head, whereas Conti use a straight solid (friction welded?) assembly 2 Quote
alextstone Posted May 30, 2020 Author Report Posted May 30, 2020 On 4/17/2020 at 10:17 AM, ArtVandelay said: IIRC, Savvy supposedly scans for a saw tooth pattern in the EGTs which is the telltale sign of pending valve failure. I would send a note to Mike Busch, they might be interested in looking at your data, personally I don’t see anything wrong till you pull the power back before EGT goes wild. They could not find any signs of failure in my data... Quote
Cruiser Posted May 30, 2020 Report Posted May 30, 2020 The failure is always the same. yours is classic. A hot spot because ................... On one hand, it is incredible that the internal combustion engine even works On the other hand, why just the #5 cylinder and not any others? They all were exposed to the same operating conditions. Let's rule out operator error. The most likely reason is the slow wear of the valve guide combined with poor manufacturing. The valve must fit in the guide and the angled surface must seat evenly all the way around. When the valve guide begins to wear (why?) it allows side loading on the valve stem from the rocker arm to push the valve a little to the side as it is opening. This side load put more pressure at a point somewhere on the seat and less pressure elsewhere. At some point the valve stops rotating. The lack of contact in the seat because of this mismatch reduces the transfer of heat from the valve face to the seat at that point. At 2500 RPM this is happening a whole bunch of times (you can do the math) Repeated cycles of less and less heat transfer from the valve face to the valve seat results in the what happened to #5 in the picture above. Quote
LANCECASPER Posted May 30, 2020 Report Posted May 30, 2020 Just now, Cruiser said: On the other hand, why just the #5 cylinder and not any others? They all were exposed to the same operating conditions. Let's rule out operator error. Since purchasing it he has replaced all of the other cylinders except #5. Since he's also had to do a lot of exhaust work, and I think a turbo, let's rule back in previous operator running it way too hot. Quote
Cruiser Posted May 30, 2020 Report Posted May 30, 2020 "too hot" is a relative value but I agree that heat is the culprit. The wear and alignment are the failures and the heat is the accelerate. The more heat the faster it happens. Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.