Mountain Pilot
Well-Known Member
- Joined
- Apr 13, 2010
- Messages
- 267
- Reaction score
- 6
A Good Story.... with a Happy Ending ( so far )
I do have to relate that I just got my Cherokee back from annual. I had not flown it since November when a broken exhaust guide was found as well as high iron content in the oil ( both fully related ). The repairs just got put on the back-burner until a couple weeks ago. I expected the worse... The bad cylinder during the last couple annuals showed about 72/80 where as the others were 74 or 76 /80 but still within the good range. Engine was smooth running and seemed to develop proper power ( within static RPM limits ) But in November during cold start-up this cylinder would loose compression through the exhaust valve but after about 15 to 30 seconds at high power setting it would return firing and all was well for the rest of the flight ( local only ) next flight the same happened so it was back to the hangar, my I/A figured it was a sticky exhaust valve common to the Lyc - O-320. I changed the oil and sent out for a analysis, then pulled the valve and found the damage.
We pulled the cylinder and found a broken top compression ring ( no damage to piston or cylinder ) and the exhaust valve could be wobbled around in the guide.
Got a rebuilt cylinder in and replaced it last week and completed the annual. Test flew it this morning.
What a difference - Please remember I am at 7,610 feet field elevation and it was 70 deg this morning and about 10,500 density altitude. Cherokee 140, VG's, Gap Seals, Prop tip Mod. Full fuel, Just overweight me in it, Take off in about 1,800 ft, 450 to 500 fpm and cruise at 132 MPH at 10,000 ft elevation and approaching redline. Best I ever got before was in the winter cold of 22 deg F was 400 fpm climb-out at 80mph and 122 mph cruise at 2500 rpm.. Summer time flying I got 200 to 300 fpm best and 110 mph cruise. I have had the airplane for 2 1/2 years and it is now like I got a new airplane. Next spring the last two high time cylinders are going to be replaced and high compression pistons installed for the 160 hp upgrade if oil sample shows Iron content back to normal.
Guess I was running on 3 and 1/2 cylinders...
I do have to relate that I just got my Cherokee back from annual. I had not flown it since November when a broken exhaust guide was found as well as high iron content in the oil ( both fully related ). The repairs just got put on the back-burner until a couple weeks ago. I expected the worse... The bad cylinder during the last couple annuals showed about 72/80 where as the others were 74 or 76 /80 but still within the good range. Engine was smooth running and seemed to develop proper power ( within static RPM limits ) But in November during cold start-up this cylinder would loose compression through the exhaust valve but after about 15 to 30 seconds at high power setting it would return firing and all was well for the rest of the flight ( local only ) next flight the same happened so it was back to the hangar, my I/A figured it was a sticky exhaust valve common to the Lyc - O-320. I changed the oil and sent out for a analysis, then pulled the valve and found the damage.
We pulled the cylinder and found a broken top compression ring ( no damage to piston or cylinder ) and the exhaust valve could be wobbled around in the guide.
Got a rebuilt cylinder in and replaced it last week and completed the annual. Test flew it this morning.
What a difference - Please remember I am at 7,610 feet field elevation and it was 70 deg this morning and about 10,500 density altitude. Cherokee 140, VG's, Gap Seals, Prop tip Mod. Full fuel, Just overweight me in it, Take off in about 1,800 ft, 450 to 500 fpm and cruise at 132 MPH at 10,000 ft elevation and approaching redline. Best I ever got before was in the winter cold of 22 deg F was 400 fpm climb-out at 80mph and 122 mph cruise at 2500 rpm.. Summer time flying I got 200 to 300 fpm best and 110 mph cruise. I have had the airplane for 2 1/2 years and it is now like I got a new airplane. Next spring the last two high time cylinders are going to be replaced and high compression pistons installed for the 160 hp upgrade if oil sample shows Iron content back to normal.
Guess I was running on 3 and 1/2 cylinders...
