Franklin Engines and Top Overhauls

[Prmetime]

Hello everyone,

I have heard it said that a Franklin engine normally needs a top overhaul at the halfway mark to TBO. I am approaching that time frame but I have good compressions and I have been doing a lot of reading about preventative maintenance and many of the articles say that it has been proven that maintenance at failure is far better than preventative at a set hour. So, is this idea outdated or has history/experience proven that a top overhaul is necessary at the halfway point?

Another data point. I recently changed my oil. The oil went from golden to Black within three hours or so. My mechanic thinks this is an indicator that a top overhaul is coming soon. Considering all the additives I have been adding to maintain my engine (Camguard being a big one), I'm wondering if it might just be the detergent agents in these additives scrubbing the engine out. Anyone care to comment?


Karl
N596C

[loganboles]

Karl,

I won't pretend to be an engine expert, but I've never heard of a top overhaul at half TBO. Another point about TBO, TBO is a number put on paper by the manufacturer. Franklin "souped up" the 150 to make the 165, then "souped up" the 165 some more to make the 180. Franklin's TBO for the 180 is 2,000 hours.

Are you doing oil analysis? How is the compression? Whwn was the last overhaul done?

Logan Boles

[Prmetime]

Logan,
I have not been doing oil analysis though I am going to start doing it with the next oil change. The compressions at my last annual (April 2012) were good. The last major overhaul was years ago, 1997 to be exact. I can't point to anything wrong with the engine. I only have around 50 hours in the aircraft and I am learning a lot about recip engines as I am used to turbines. I am still "learning" the idiosyncrasies of the engine and my airplane. My only issues have been having to rebuild the starter, and two stuck exhaust valves. As I now use MOGAS as much as possible, I expect the stuck valve problems to go away.

Karl

[hohanshelt]

I have just completed an extensive top overhual on my F-150. The engine was acquired from another aircraft with only 540 hours since overhual, however that overhual was in 1963! Obviously I wanted to replace all gaskets and wanted to get a look at the crank journals before investing any effort or cash in the engine. I also had no information on whether an oil filter had been installed which was fairly unlikely in those days. I consider the oil filter to be even more important to engine life than the use of modern lubrication oils. So the net result was that for $2700 in parts and cylinder labor, I got an engine with new cylinder liners, a valve job, new rings and rod bearings, all new gaskets, and all top end parts within the clearances allowed for a new engine. This is a small price to pay to eliminate most of the unknowns of an engine before it is installed in the aircraft.

[Prmetime]

Bob H,
This isn't an engine that I purchased with an unknown pedigree. I have full logs for it from the day it was new. I have the full data of the major overhaul which includes a brand new 220HP crankshaft and it has had an oil filter since at least 2003. My question is this. If everything appears to be running well, would you just top overhaul an engine just because it hit halfway to TBO? I am trying to learn if Franklin engines really do have that sort of problem/requirement and I think the answer is no.

Karl

[hohanshelt]

I see no need to do a top O/H (or even a full O/H) if:

1. The engine is operated regularly and flown at least 4 hours a month (more is better)

2. It is run on Mogas or TCP is added to 100LL

3. An oil filter is installed and the oil is changed at 25 hours

4. The owner has knowledge of the engine history including everything that is not in the logs

5. No problems are encoutered like sticky valves, low compression, or high oil temps

Most of our Stinsons have around 2500 TT which works out to under 39 hours a year or 3.2 hours per month.
Unless you recently reached puberty even a 1200 hour TBO is likely to last your flying lifetime.

[Eddie Stewart]

If the compressions are good and oil consumption is reasonable, fly it like you stole it. Run mogas in it and fly it often. No need spending the money for a top overhaul if it is not needed. Eddie Stewart N537C 108-3 that is getting a 470 installed.

[Prmetime]

Thank you all who responded. I appreciate the back up.