Back near the end of May I decided to pull the engine for an overhaul for a
couple reasons. For more years than I can remember I have had a oil leak which
I knew was from a crack in the block. While this may sound very on safe it
never became a structural issue but only caused me a large amount of cleaning
and adding a quart every10 to 12 hours of operation. This past winter it became
apparent that the leaking was increasing to the point that it became a real
irritant. The thing that made the deciding factor was during a afternoon flight
I noticed a drop in oil pressure while nearly a hour from home. I never lost
pressure but the lowered pressure was a another cause for concern. I always
felt that an accident is a build up of 3 mistakes and I had 2 already.
I had a block preped by Roy a few years ago and I had a store pile of parts
so I figured a several week turn around and be right back at it. Well, that
didn't work out so well. Through a number of comedy of errors (not really
funny) and 4 separate tear downs and test runs and even a couple test flights,
I finally have everything running great again. The first big deal was I knocked
the block off the work bench when it was short block assembled. From there i
convinced myself that it had distorted the block and it was trashed. MArk
Lankford came to the rescue by sending me his 3100cc block. I built that all
the way up and mounted it to the plane. I knew that it was very tight build. It
proved to be to tight with high oil temps and scorching a bearing that was
tight. So back off the plane and tear down again. I tore the high volume oil
pump apart again and looked the gears over again. There was no sign of wear at
all but using a magnifying glass I noticed that there were some circular scores
just above the drive gear. The drive gear is a pressure fit to the shaft. It
appears that the gear when up to temps became loose on the shaft and would slip
some. I replaced the drive gear and hoped I had this resolved.
Over this period of time I re-evaluated the case that I had dropped from the
work bench. Other than a dent in one corner of the casting I could not find any
misalignment or damage at all. I re-installed 2 different cranks and cams to
torque and found that the cranks run perfectly true and free. So I took
everything back off Mark's case and started to rebuild mine again. At least
Mark's is all cleaned, painted and ready for him to start his rebuild.
I built this one up again and mounted it to the plane again. This time it
seemed to go together OK. A couple more weeks altogether and mounted it back
up to the plane again. It started up OK and timing was checked. Something
bothering me...It didn't sound quit the same. I did a test flight of about 20
minutes around the pattern and it still bothered me. I had one head temp that
was a bit high. But worse yet I had oil all over things again... That just
isn't going to due again. I cleaned the engine all up again and put the dye in
the oil that ultraviolet light shows. I ran the engine on the ground up to
temps for about 15 or 20 minutes.
My son and I pulled the engine again, took it home back on the bench and
search out the oil leaks with a black light in the dark. To my surprise none of
the leaking was coming from where I thought it was. I only had one O ring on
one push rod tube that was leaking a bit. All the rest was coming from the
edges of the top cover. Well at least it was an easy fix for that part. The
noise that was troubling me was the next thing. I just had an uneasy feeling
about the valve adjustments. When I pulled the cover on the right side I found
the middle rockers loose on the push rods. I had miss adjusted a least one set
somehow (inept or incompetent come to mind) I did not even bother checking any
others. I pulled both heads off, push rod tubes pulled out the lifters. I took
each lifter apart in order and drained them and replaced them in order.
Reassembled the right and then the left sides with all new O rings again. I
carefully adjusted the lifters in order and repeated to verify.
The oil with the dye was left in the oil pan just in case I discovered
leaking again when it was back on the plane. The engine went back on again
yesterday. Everything went well which made the process feel better. Nothing
seemed to be nagging me this time. I finaled everything out this morning and
with my son at the throttle we checked the timing again. The engine fired right
up with just a couple cranks and ran very smooth. Nothing bothering me this
time... sounds great and seemed like it had great power. After a few minutes of
running and warmed up there was no obvious oil leaks either.
I got everything all cleaned and back under cowl. Started her up again and
did a bit of taxi. Really acting great now and very good power. I decided that
the only way to really find out was to fly. The take off was good with all
temps being very normal as compared to the past 12 years. I flew for an hour
with one full throttle run at 3000 feet just to see what happens. Like I said
the power seems really good. At 3250 rpm she was bouncing the true airspeed at
183 to 184 mph a solid 3 to 4 better than i have been able to achieve before.
I didn't mention the details of what was actually done in the rebuilds. The
main bearings and rod bearings were replaced. The exhaust valves replaced. All
valves were lapped. pistons removed and inspected, rings inspected cleaned and
re-installed. New fifth bearing shell installed. New plugs. New oil pump gears.
New silicon exhaust gaskets. New cylinder head and base gaskets. Mostly all new
instrument sensors. all new gaskets. New bypass spring and piston. Replaced
spark-plug wires. Lots of cleaning and rechecking every part for condition. All
in all if it wasn't for the oil leak that has plagued me I would not have been
afraid to have run this engine to 1500 hours or beyond.
There was a period of times during the past 6 months that i was ready to
call it quits, This rebuild was about the most frustrating thing that I have
ever done. I fully admit that several of the things that went wrong were fully
and completely of my own making. But I flew my plane today and man oh man does
it make it all worth while.
Keep building guys,
The sky is waiting,
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