How many times can you rebuild a Lycoming?

rv9builder · #1 09-06-2007, 02:16 PM

How many times can you rebuild a Lycoming and have a reasonably good chance of reusing expensive stuff like the crank and the case?

Thank you,

rgbewley · #2 09-06-2007, 03:53 PM

Too many variables to say for sure. A Lycoming c/s can go four sizes, Standard, M003, M006 and M010 on the rods and mains. So, there are three if there's nothing else that comes into play, i.e. propstrike that requires a regrind, oil starvation and cracking (just saw that on a 500 hour engine where the pilot hangs it off the nose - but I don't suspect you'll be doing that in an RV

) Of course, the bearings get more expensive when you go oversize.

The cases can be much more difficult to say. Wear and tear during the normal course of operation and the quality of any previous weld repairs play a huge factor in it.

Make sure if you're looking at buying a core that you make sure the seller will warranty the crankshaft and cases as repairable.

gmcjetpilot · #3 09-06-2007, 05:21 PM

I asked Lyc that. There are no time limited parts. You will wear it out before you fatigue it out. Of course Lyc recommends not using old cylinders. So I suppose that's an indirect comment about a time limited part, the cylinders, but you can reuse them if you want. Rhonda Barrett-Bewley can tell you how many overhauls you can get. I think its so dependant on operations. Since many engines fly so little they time out before hour out. This is no record but I know of one Lyc rebuilt 3 times. It was pushing 8,000 hours and probably rebuild #4 last I saw it. Not many GA pilots even put 8,000 hours in during their whole life. I recall one Lyc rep told me he saw one with 16,000 hour total time and countless rebuilds. What got replaced and what was reused I don't know.

PCHunt · #4 09-06-2007, 05:37 PM

Reminds me of my Grandfather's ax that I have out in the shed. I've replaced the handle 4 times, and I've replaced the head twice, but it's still "my Grandfather's ax."

RV6_flyer · #5 09-06-2007, 06:08 PM

I am probable going to repeat what the others have said in different words.

When you cannot buy replacement parts any more. Replacment crankshaft and replacment case are the two parts that come to mind that can make the overhaul / rebuild cost more than a replacement engine.

rgbewley · #6 09-07-2007, 09:33 AM

Quote:

Originally Posted by gmcjetpilot

I asked Lyc that. There are no time limited parts. You will wear it out before you fatigue it out. Of course Lyc recommends not using old cylinders. So I suppose that's an indirect comment about a time limited part, the cylinders, but you can reuse them if you want. Rhonda Barrett-Bewley can tell you how many overhauls you can get. I think its so dependant on operations. Since many engines fly so little they time out before hour out.

I agree that most pilots will never put 8000 hours on an engine, and many if not most engines go to overhaul before they reach TBO hours. The lack of hours on an engine is one of the most common reasons engines go to overhaul (cam corrosion, bearing failure, etc., etc.) Not sure who you talked to at Lycoming, but Lycoming has a 12 year timed out limit on their engines, so every mandatory part at replacement per Lycoming SB 240T has a 12 year time limited life, don?t you agree? True, cylinders are not mandatory replacement at overhaul. However, given the competitive pricing of new cylinders and (overhauled cylinders might run $300 less apiece than new, if they don?t require welding, chroming or CermiNil), and the likelihood that overhauled cylinders won?t make it to the next overhaul (especially if they are chromed) make replacing them a smart financial decision over the life of the engine.

Jconard · #7 09-07-2007, 12:17 PM

Some engines make it through overhaul without a crankshaft grind, or case work.

I got lucky buying a runout O-320 A3B off a twin commanche, and the bearings on the crank could be lightly polished, and the case required not work beyond cleaning...no fretting etc...The particular plane the engine was off spent most of its life in commercial use, then the engine spent 100 hours on a single hole pitts.

So if the crank can be ground four times...and you get do it every other runout...it gets pretty long.

Most of the pre-TBO overhauls I have ever seen or heard about were from low usage craft...corrosion on the cam or lifters, or prop strikes where it was financially attractive to rebuild during the inspection.

JMHO YMMV

jeff beckley · #8 09-07-2007, 05:25 PM

My 0-360 had it's third O/H when I bought it. The crank Still did not need ground. It was closer to the top factory new limits. My cam only needed a polish and the lifters were a light grind. The case had some modifications done to it suggested by "case works" but it needed no repairs. My engine had 5934 TT when I bought it before I had it overhauled. It has a few overhauls left provide I take the same care as the previous owners had.
BTW. The cylinders were junk and I replace them with new.