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To rebuild or not to rebuild... or swap altogether

What would you do?

  • Throw an oil pump in the A1F6D and keep an eye on things

    Votes: 14 51.9%

  • Rebuild the A1F6D while I have it apart to replace the oil pump

    Votes: 3 11.1%

  • Install the A1A. A Cardinal owner needs the core.

    Votes: 1 3.7%

  • Rebuild and install the A1A

    Votes: 3 11.1%

  • Something else

    Votes: 6 22.2%
  • Total voters
    27
G

Gearhead51

Active Member
Patron
My RV6A is 32 years old and has a 42yo O-360A1F6D out of a Cardinal. It has ~2300h TT, 74+ compressions, low oil consumption, and borescope looks ok. It has 2 rear cyls that are @ 500h or so. Besides that, I don't see that it has ever been opened up. There is a little lead on the heads near the valves, but I believe that is due to not running hot enough to scavenge the lead. It runs really cool even during the 90+ degree Missouri summer. It is able to propel my 6A to 161kts @ 3000' during the summer @ 2600RPM with a Sensenich wooden cruise prop (71"dia 83" pitch), so I THINK it makes ok power. It's time to change the oil and cut open the filter, but before I do...

When doing my first condition, I found out that my engine has an oil pump AD from 1996 that was not logged in the book. The AD from '81 replaced the sintered metal gear, but left the aluminum gear... hence '96 AD. Anyway, it's grounded for the aluminum gear AD. I was given a magnet on a stick and some instructions on how to determine if the AD was done without pulling the housing, but the instructions don't take the A1F6D accessory housing into account. This engine obviously has a counterweighted crank that reduces prop restrictions when I go to a CS prop. I will also likely switch it to a single mag and SDS ignition if I keep it.

I also have an '04 O-360A1A 1700htt 600STOH with new cyls and pistons. The logs say it was owned by Bob Axsom for most of its life. This one has Airflow Performance FI, so I'll have to upgrade the fuel system to high pressure and find an ignition system for it, since I don't have the mags.

I got a great deal on this plane knowing it wasn't perfect and would need some work. I was ok with that because I wanted to make it exactly what I wanted.

Given the options, what would you do?
1.Throw an oil pump in the A1F6D and keep an eye on things
2.Rebuild the A1F6D while I have it apart to replace the oil pump
3.Install the A1A. A Cardinal owner needs the core.
4.Rebuild and install the A1A
5.Something else

Thanks for your time.
 
Sam,

Thanks for your reply. I'm new here, so I was asking for the opinion and thoughts of more seasoned individuals. I've read a bit about infant mortality on rebuilt engines and not cracking them open unless you have to and I've read about spalled camshafts in enginesthat are old like mine. I can spend money frivolously or be miserly to my own detriment, but I don't have a feel of what is prudent vs. risky.

I read about counterweights being upset by rapid throttle movement, but I don't know what "rapid" means. I feel a 2 Mississippi should be ok. Oil pump drive for a A1F6D is $1800 or so. It seems like everything for that engine is excessively expensive.

My mission will be traveling with some gentleman's aerobatics in a few years. I've got good friends, but I really thought I'd reach out to a broader audience.

To answer YOUR question, I'm comfortable on a Ducati running up the hill at Road Atlanta, or touring on my K1200GT, but those experiences don't really translate here. ��
 
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If I understand that you're just asking for opinions:
Having moved from a carb to fuel injection, I love the balanced feel (I've balanced the cylinders with relatively inexpensive nozzle adjustments) and ability run lean of peak. I'll never go back to a carb.
 
The parts manual should show that, and a close reading of the AD should identify the engines it refers too. So that's easy to determine.

Dave
 
FWIW (if anything), I have a 42-year-old IO-360-A3B6D in my -6 which I overhauled in 2008 with 2100 hours since new on it back then. The engine had never been apart until I got it. The oil pump AD applied to this dual-mag engine too, so I diligently replaced the gears during the overhaul. Well, the original aluminum/steel gear combo looked like new when I took it apart, so I wondered why I bothered.

On the other hand, pulling the accessory housing off is not that difficult. Just need a Harbor Freight cherry picker to support the engine. Besides, the oil sump and accessory housing have got to be leaking oil by now, so a good excuse to replace those gaskets.
 
Mysomethingelse

Go fly, do nothing, keep eye on things. Looking like oil pump issue not applicable to you…yeah. If you get new, rebuilt etc, that takes time to get…. Go fly !
 
Sorry if I missed it, but why change the oil pump if there have been no issues in 2300hrs and 40 years? Being experimental, you are not mandated to comply with ADs. The nice thing is that you can use your judgement and not that of the lawyers. If the engine is otherwise performing as it should, I would continue to enjoy it. I faced the same issue with a A1A back when it was issued. "No action" was the thought of the times, and for all I know that airplane which is still flying may have the same pump in it.
 
That is a judgement call based upon your risk tolerance. That engine could easily go to 3300 or it could grenade at 2305. There are reasons for the TBO recommendation beyond lawyers. Remember that these recommendations were produced 70 years ago, long before lawyers changed the way we do things in this country. Go look at the instructions from a toaster sold in 1950. Doubt you will find 3 pages of warnings about how you can kill yourself with it. I doubt you will find ANY warnings. Back then, we didn't need to state the obvious to protect ourselves from lawsuits.

These recommendations were put in place because several parts in that engine are NOT expected to last forever. They believed that at 2000 hours enough of this wear could become problematic in some percentage of engines. We are dealing with averages here and there will always be outliers. Yours may be out on the fringe and is no where near wear or stress limits or it may not. There is really no way to tell. Some of those parts are to be replaced and others are to be inspected. But universally, each eithe has a limited life or potential stress related damage and therefore a risk.

The gear AD is due to a number of failures that are beyond what was expected. Certainly the vast majority of them did NOT fail. However, enough did that someone decided that the design was flawed. I have my doiubts that if it made it to 2300 hours it is at any risk. However, you don't really know why they fail, so can't really say whether or not the 2300 hours of use puts you in the clear or not, though my suspicion is that you are in the clear.

On the flipside, you have an engine that has proven to be robust and plenty of folks have seen serious issues in their engines early in their life due to product flaws or QA issues. So new or rebuild with new parts is NOT universally better.

And on the flipside of that is that time is the enemy of metal parts exposed to lots of heat cycling and sliding metal on metal contact, as well as stress.

I won't provide an opinion here as this is a VERY personal decision. Just wanted to give a little meat to chew on as well as to make sure you understand that TBO is NOT just a lawyer thing. All engines wear and produce stress and have the potential to fail due to that wear/stress. The difference between airplanes and everything else and the reason for the TBO is that the consequences of failure results in more than just the need for a tow truck and an undesired trip to the mechanic. With "Everything else" you just run it till it fails and then fix it or scrap it. Lots of folks have "thrown a rod" in their car. It is mostly an annoyance; Not so much in an airplane. I used that example because rod bolts are one of those items exposed to a lot of stress.

Larry
 
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Lycomings typically don’t “grenade”. They almost always give plenty of warning well before they go south. Not that they can’t blow up I guess, at anytime, even when new.
That said, I have a hard time doing work on a high time engine just to keep it going. At some point, it’s not worth trying to buy time.

Bob Axom was a very active racer. He posted often and you can search for his posts. He passed a few years ago. That engine was probably ran hard, which isn’t necessary a bad thing. Bob seemed responsible and knowledgeable. Still, a lot of racers push the rpm limits.

I like Sam’s post. You’re going to get a wide spectrum of opinions and it’s going to come down to what you’re comfortable with.
 
You asked for opinions, here’s my $.02.
As stated it’s got 40 yrs experience and 2000+ hrs. Solid, stable, minimal oil burn, all good signs. If you crack it open even for the pump you stand a chance at it making a mess. Listen to it, it’ll talk to you. See any significant changes have the other bullet on the stand ready to bolt up.
There is always risk. To me it’s very acceptable, to you?
 
JonJay said:
Lycomings typically don’t “grenade”. They almost always give plenty of warning well before they go south. Not that they can’t blow up I guess, at anytime, even when new.
That said, I have a hard time doing work on a high time engine just to keep it going. At some point, it’s not worth trying to buy time.

.
Click to expand...

Yes, I used an extreme example by using the term grenade. What I meant was a catastrophic failure, like throwing a rod, which will typically tear a hole in the crankcase and engine will seize within a few minutes due to oil loss and it does look like a grenade went off inside the engine. I will please ask you to prove that no lycoming has EVER thrown a rod. Plenty of Lyc's have swallowed an exhaust valve, resulting in serious engine failure, typically without any signs in advance.

Here is a link to a mike busch article with pics about a thrown rod on a continental https://resources.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2014-06_cylinder-work-be-afraid.pdf Here the pilot was lucky that the rod came through the top of the crankcase.

I disagree that these or ANY engine for that matter will ALWAYS give plenty of warnings before failure. IMHO this is dangerous advise to give and doesn't reflect reality. There are many potential failures that DO NOT give warnings and that applies to new engines or those with 2300 hours. Logic and experience tells us that, excluding failure due to defective parts or bad design, the engine with more time has a greater risk than the engine with less time. I am excluding the first few hours of a new engine to account for issues in construction or parts.

In this realm of risk mitigation it is all about MTBF. That can be determined by engineering analysis or real world experience and is usually based upon least common denominator. I can't say that lycoming got it right or wrong with 2000 hours, but have ALL confidence that it will not run forever, as almost no combustion engine will. The challenge is picking a number of hours where the odds become strong enough against you or exceed your threshold.

There is no fear mongering here and am not trying to convince anyone that they should stop using their engine at 2000 hours or any other number. Just trying to keep a balanced discussion about risk vs time.

Larry
 
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Thanks for the input guys. On top of asking if I should rebuild, I was hoping to get some input on the 2 types of cranks involved. I went out to the hangar to measure some things, and I noticed that the A1f6D has a more compact accessory housing. At the very least the A1A will need a remote oil filter since my 6A doesn't have a recess in the firewall. I also need to look at the prop governor mount location.

I've ready quite a few of Bob Axsom's posts. His logbook entries are pretty thorough.

I see some people voted for something else. I'm looking for those alternative ideas as well.

Happy Holidays!
 
Gearhead51 said:
Thanks for the input guys. On top of asking if I should rebuild, I was hoping to get some input on the 2 types of cranks involved. I went out to the hangar to measure some things, and I noticed that the A1f6D has a more compact accessory housing. At the very least the A1A will need a remote oil filter since my 6A doesn't have a recess in the firewall. I also need to look at the prop governor mount location.

I've ready quite a few of Bob Axsom's posts. His logbook entries are pretty thorough.

I see some people voted for something else. I'm looking for those alternative ideas as well.

Happy Holidays!
Click to expand...

This, https://vansairforce.net/community/showpost.php?p=1618177&postcount=12 will solve that problem.
 
As someone who has not had a plane to fly for several months now (cam failed), I suggest that the time to build a motor is while you have one that is working.

The turn time for machine work is months long with no let up in sight. Some parts are difficult to obtain so if you want to avoid being grounded for several months, you may want to build a fresh motor now.

It sure is a lot more fun to take your time and build a strong motor while you still have your plane to enjoy.

Happy Holidays
 
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