Engine
Rebuild
Start: 05/30/09
Finish:
Total Time: 75 Hours
This isn't something covered by the plans,
so while it relates to chapter 23, we felt it best to separate this task out.
The engine we purchased had over 2800 hours on it since it's last overhaul.
Considering the recommended Time Between Overhaul (TBO) from Lycoming is 2000
hours, we knew when we bought it that we'd have to rebuild it before flying with
it.
The plans suggest finding a mid-time
engine that is proper working order so that one isn't proving out an engine at
the same time as the airframe. This is great advice, and had we found a
mid time C1C when we needed to purchase we would have used one. Rebuilding
will give us a better understanding of the engine though.
After removing the engine from the
airframe when we were done with fitment, the first step was to disassemble the
engine for cleaning and measurement.
We found a number of cracks in the
crankcase after we got the sump and the cylinders removed. While we're
aware that crankcase cracks are not uncommon, we're not familiar enough with
these engines to determine which cracks can be repaired, and which, if any, are
cause for discarding the case. We'll leave that determination to the
experts at the engine shop. We're not particularly worried at this point
though, as the business we purchased the engine from is reputable and guarantees
the cases and crankshafts to make overhaul. Swapping out the case would
only take a quick lunch hour errand.
As suspected, the extensive cracking in
the crankcase was cause to reject it. It could not be repaired, so new
crankcase halves were required. Wentworth Aircraft, where we purchased the
engine, found suitable replacements, and delivered them to Bolduc Aviation (our
chosen machine shop). The new case was inspected, found serviceable, and
cleaned.
The crankshaft was also inspected, found
to be in great condition, requiring only minor polishing (no undersizing of
bearing surfaces would be required). The AD for the crankshaft gear was
performed, and the rods were reconditioned and reassembled onto the crankshaft.
The IO-360 rod bolts are tightened to length, not torqued to spec, and this is
not a procedure we were familiar with, so we had Bolduc perform this step.
Our first step in reassembling the
crankcase (after finishing the cleaning and inspection of all parts), was to get
the one piece oil seal installed behind the prop flange. This sounds
simple enough, but stretching it over the flange requires a lot of grease, both
elbow and conventional.
The bearing surfaces are then lubricated
and the crankcase mating surfaces are prepared for joining with anaerobic
sealant and silk thread. The two piece front bearing on our IO-360
requires care be taken to mark the alignment of the bearing in the case, when
installed into the dowels for it. With the crankcase assembled on the
engine stand, we can now install the cylinder assemblies, and the accessory
housing.
With the major assemblies together, we
painted the engine. The color scheme we decided on for our engine is blue
with black accents. It might be a bit much blue, but overall, we like it.
With most of the engine assembly complete (just need a new fuel pump and an
ignition system at this point), we're about ready to bring it to Bolduc Aviation
to be run in on a test cell.
After installing a new fuel pump, and
procuring the ElectroAir ignition systems we transported the engine (including
the GRT engine monitor) back to Bolduc for initial run in. Video from its
run in can be seen here.
We had two minor issues to deal with after
run in. First, the map sensor on the secondary ignition control unit
(which was purchased used) was malfunctioning, causing that unit to lag the
primary by 6-8 degrees. The engine still ran fine, but was about 50-70 rpm
below the peak we were expecting. Second, my 'guess' at the midway point
on the oil pressure regulator setting about a turn too low, causing our peak
warm oil pressure to be about 68-70psi or about 10psi low.
Aside from that, run in went very well.
Peak CHTs never passed 370 deg, and peak oil temp was 172deg. After a
couple hours of run in we drained the oil, ad cut open the filter. Both
were very clean, and we deamed the engine fit for flight.
