PA 24-250 engine overhaul / prop alternatives

[Randy Jones]

I am planning to overhaul the IO 540 C1B5, injected 250HP engine in a 1963 PA 24-250. After that, I will want to replace the original 2 blade Hartzell propeller which is subject to a recurring A.D. I have some specific questions and would like to hear any advice from fellow Comancheros out there:

1. I have heard of overhauls where the engine is essentially rebuilt as a 260 HP @ 2700 rpm engine (vs the stock 250 HP @ 2575 rpm). I understand this has to do with counterweights or vibration dampeners. Is there an STC for this or can a shop simply rebuild the engine to a different Lycoming spec?

2. I am looking at 2 prop alternatives: The McCauley 3 blade Black Mac, or a Hartzell - JAS 2 blade. The McCauley adds about 10 lbs, and has a 77in diameter. The JAS (Johnston) prop is about the same weight as stock, is 79 in diameter and requires counterweights to be added. Both are about the same price (~$12,500).

3. I am in So California and am looking at 2 shop alternatives: Tim's Aircraft Engines in Long Beach and Johnston's Aircraft Services (JAS) in Tulare. I have only heard good about both shops so far.

4. OEM Lycoming or Superior cylinders? Aviation Consumer magazine reports fewer complaints with OEM, but thats on a wide range of engines and not specific to the 540. OEM is about $1000 more for the set.

[Kristin Winter]

I thought Johnston had the STC for some engine conversion. I am fuzzy on details.

I have a lot of respect for Tim's and no info on Johnston.

I would only do Lycoming cylinders. I see less problems with them.

[Randy Jones]

Kristen, thanks for the input on shops and cylinders.

The Johnston STC allows use of the newer prop on the 250 engine, which gets rid of the recurring prop AD. While it involves counterweights (or vibration dampeners) internal to the engine, it does not increase the rpm red line or horsepower, according to the people I have talked to at Johnston. The same prop also goes on the 260HP engine, without the need for the internal counterweights.