I did not get to heavily into the details with our Mech and the Engine
Overhaul shop. But I do remember them stating that the different piston had
a slightly higher dome creating a higher compression.

One thing we did find after we were flying again, we also installed the
lightweight Sky Tec Starter and the lighter propeller approved by the
original PA-25 Type Certificate. While static run up was within limits
according to the STC and TCDS, when taking off with no glider in tow and not
maintaining minimum climb airspeed you could go over redline on the tach,
any climb speed higher than 70knts requires close attention to the tach
redline limits.

We are flying approximately 1200# below Max GW with full fuel on board.
Don't even feel a 1-26 on tow and the vario is useless to the glider pilot
in a 1-26 because it is always going to read over 10knts up.

BT

"Jim Burns" wrote in message
...
Thanks BTIZ. "new pistons and rings" Do you know if the piston change
increased the compression ratio or changed the displacement? or was the
change simply necessary to handle the increased RPMs?

I believe that Lycon has been working on a STC for several years that
would
increase the compression ration of the 540 to 10:1, similar to what as it
has been supplying to some of the airshow pilots. Not sure how far along
they are with the process.

Jim


BTIZ wrote:

Jim, two STCs for the Piper Pawnee
First, STC SA1433GL allows upgrade of a Lycoming O-540-B2B5 or B2C5 at
235HP
to a O-540-B2B5-CA1D5 or O-540-B2C5-CA1D5 engine at 250HP at 2575RPM.

Second STC SA1436GL allows installation of the modified engine into the
PA-25-235 airframe.

Both are owned by Howard Kron of Howards Aircraft Service in Clara City
MN.
Both can be found on the FAA web pages if you look up the STC number. The
fee to Howard for the STC is cheap, around $200 and the only parts were a
different piston and rings into the standard engine. We did this upgrade
during an engine overhaul.

BT

"Jim Burns" wrote in message
...

"BTIZ" wrote in message
news:VamWf.498$CL6.78@fed1read11...
in the 0-540 with a 250HP STC.

BT... can you tell us what the 250HP STC entails for the 0-540, the STC
holder and which airframes/engine models it is available for?
Thanks,
Jim