Engine Replacement Criteria

[saybeengineering]

I have a Long EZ 950 hrs with an O-320-E2G 160 Hp Engine which has 550 hours after its top overhaul. The Total time of the engine is 2240 hrs. Just replaced one set of rings in on the cylinders, compression are in the 70s. However, starting having some minor engine issues and oil consumption has gone way up and we are suspecting its going through the intake valve.

Nevertheless, I'm a bit cloudy with respect of the TBO of the engines, replace the cylinders or exchange the engine. I stop flying to determine my options. In the certified environment the TBO is well established, what in the experimental environment? What options could be considered for this engine/scenario? Exchange ( if $$$$ available)? Major overhaul? Limitations... Thanks in advance.

Afif Saybe
LONG EZ HR-ATQ

[tdarden]

I would encourage you to read articles by Mike Busch on this topic.  Try googling his name, or look at his website, Savvy Aviator.  If you want to save a lot of money, sign up for his Savvy Aircraft Maintenance Management service for $750 per year--they act as advisors regarding all maintenance decisions for your plane, which is really valuable at times like you are going through now.  They tell you who to use for different services and bring data and experience to your decisions.

Regarding TBO, it only has legal relevance for Part 135 planes (basically for-hire planes), which have to be rebuilt at TBO.  Part 91 does not require adherance to TBO times for certified planes, nor do TBO's apply to experimentals.  Increasingly, smart operators are using engine condition instead of time to decide when to overhaul.  Related, the data increasingly are showing that engine maintenance itself causes many failures, so it is foolish to replace good parts just based on time because you increase risk of failure.  There are a few exceptions, such as magnetos which apparently do wear based on time.  But, to make decisions based on condition, you need good data, such as oil analysis and borescope observations of the condition of the valves and cylinders, as well as EGT data for each cylinder, which most Long EZ's do not the equipment to capture.

I don't have any thoughts about causes of your oil consumption problem.  I did not know that you could lose a large quantity through a valve guide, as opposed to through the rings or by blowing it out--but ask an expert, which I am not.  I assume the bottom end is in good shape because it only has 950 hours, although the oil samples could confirm this.  If that is true, then clearly you would be better off repairing the cylinders instead of overhauling the whole engine.  Too bad they did not replace the valve guides when they replaced the rings.

Best wishes. 

[Bill James]

Good advice from tdarden.
My point here is detailed records. I should assume you have a rock solid track on all of the indications you are interested in on your plane, and will have little use for encouragement to keep detailed records. But here goes-
I am not naturally a detail person. However, the Eze life has forced me to become appropriately more so. Paying more attention to certain things often results in an overall awareness that kinda expands. Luck and preparedness has resulted in catching several significant events early. And there are actually more benefits now that I pay more attention to my surroundings besides my wife and i having higher level, more detailed arguments.
Besides the four notebooks of fabulous ideas that i didn't end up putting on the plane, i have several notebooks of lists consisting of everything i could remember from particular flights. I was inspired by a retired test pilot that after shutting down sat in his SX-300 for a good ten minutes writing notes, i assume about the flight. Ten minutes is a long time to stand there in the hot sun waiting for him to get out so you can just touch the spectacular aircraft helping him push it into the hangar.
To make this shorter I will just mention that from two pages of notes over a couple of months i was able to pull four seemingly unrelated things together to pinpoint a bad intake valve seal. We didn't know it was leaking and causing the plug to foul. This was combined with an erratic electronic tach that got its reading from the plug wire on that cylinder. Because it was erratic it took me about four weeks to confirm all this. Nice thing was the bird was safe and we were in the air instead of in the engine rebuild shop. After I took the cylinder in for rework and had three weeks of uneventful aerial bliss.

Then the engine started missing erratically again. Since i had had the cylinder fixed, i proceeded to remove a unique intake tube which i surmised must be the problem. But no. It still missed occasionally.  We retraced the problem using the same checklist as before and viola, against the odds, it pointed to a leaking intake valve again.
The detailed records (finally getting to the point here) helped us to confidently return our gaze to the leaking intake valve, which had supposedly been fixed. When i returned it for inspection they said "oh no, even though we normally do mostly exhaust valves,  we actually did do your intake valve, really... but ... just for you we will redo the intake again for no charge."   
What do you know. They did the intake valve and no more erratic firing or erratic tach readings. And the reinstalled innocent intake tube worked fine, as always. 
At first, the myriad indications seemed overwhelming and unrelated. Now looking back, it seems anyone could have figured it out sooner.
This is an example of several fairly minor issues that have been resolved fairly simply and economically.
Point is, performing safe flights we can make some pretty gratifying progress on pinpointing what the real problem is while benefitting from our proximity and interest in the plane.
 And like this note, no charge      

[saybeengineering]

I thank you both for taking the time to put your thoughts together and provide useful advice of a really sketchy topic.

I was tempted to continue flying but deep inside, i aborted two take offs because things were not like there suppose to be (engine wise). I grounded the airplane till I could correct the problem once and for all. I felt frustrated because my mechanic was playing hit or miss with the diagnostic. This particular event has been very educational and evaluating different perspectives of "engine maintenance" in contrast of what the manufacturer or greedy mechanics say.

Since I posted my inquiry, I did a lot of test to further diagnose my original problem till I decided that the cylinders needed to be inspected further. Cylinder number three had a broken ring. I month ago, I had a similar leak on Cylinder number 4 and a broken ring was also found. So I decided, to change all of them. Nevertheless, after further cylinder inspection, my chrome cylinders needed work given that the ring tolerance inside the cylinder exceeded on all of the cylinders. The intake valves also had some wear. Crankcase and derivatives looked normal and no major issue there. Since we don't have a shop here to do that kind of job, considering the hours on the engines and the "ifs" of the last top made on the engine, I decided to purchase 4 new cylinders for the 0-320. No, I don't have money to spare. However, I really want to enjoy every time I go flying, not worry every flight of the other 'ifs" of the uncertainty of a "unhealthy" engine. I fly in 100% rugged terrain and in a tropical environment all the time and performing safe flights is of my highest priority. Also, honestly, I do hate down time, too!!!! I should be receiving my cylinders Thursday and will work on them on the weekend.

Once again, thank you for your thoughts and considerations to a fellow Canardian in need!!

Regards,
Afif Saybe
LONG EZ, HR-ATQ
Honduras

[Skywalker Aviation]

I know it has been mentioned, but its amazing how a $30 dollar oil analysis can be a HUGE life saver in preventative maintenance.

- Derek