Planecrazy232
Well Known Member
I’m working on converting my FP back to CS and while the crank plugs were out I figured I’d give this a try. I was able to see all 6 lobes. This is a narrow deck O360.
OK - excellent - now how did you do that? What kind of super-pretzel borescope are you using there?
I’m working on converting my FP back to CS and while the crank plugs were out I figured I’d give this a try. I was able to see all 6 lobes. This is a narrow deck O360.
Excellent to know that this can be done! I have thought of dropping the oil pan, but there does not seem to be a way to access from there.
Sump removal is way less destructive than barrel removal.
Your luck may vary Art
I am impressed! I can imagine how one can see w/o the back plug for a few lobes but will need some 3D view of the guts to process how this works.
All these years, all the risk assumed, or barrels removed, to pre-buy the lobes and it is right in front of us all!?!?!
Does this work on all (Lyc) cases and non-solid cranks?
I am struggling to visualize how a scope gets from the forward hollow portion back into the core of the crankcase. It has been a while since I looked at a crankshaft and just cannot get my head around the path.
Hoping the OP will share more detail.
Larry
Here I am- I wish I took more photos and video during this but I was on a different path at the time...
On my hollow crank, the rear plug (about 8" back from the front) looks like a freeze plug. Some of these hollow cranks have a small pipe plug in this location, so I'm not sure if the borescope will go through that small opening. This "freeze plug" was not in place on my engine (set up originally for fixed pitch). So when I pulled the front plug and looked inside past where that rear plug would go, I saw connecting rods. I turned the crankshaft and the rods moved out of the way. That's when I got the borescope idea. The VA-400 borescope is about 20" long and has an articulating head. I inserted the scope and when I got to where the rods were, I articulated the camera head upwards and viola- there was the cam! I then straightened the camera and inserted farther in until the next opening and articulated up again for the next set of lobes. I then went farther back yet (the whole length of the borescope was inside, including the handle stuffed inside the snout of the crank) and was able to see the last set of lobes.
If I ever get the chance to do this again I will certainly document better. Better yet if someone has an engine apart with the case halves open that would be a great tutorial.
I'm confused! But I know this is really interesting, since most people have said that it can't be done.
View attachment 15060
Here I am- I wish I took more photos and video during this but I was on a different path at the time...
On my hollow crank, the rear plug (about 8" back from the front) looks like a freeze plug. Some of these hollow cranks have a small pipe plug in this location, so I'm not sure if the borescope will go through that small opening. This "freeze plug" was not in place on my engine (set up originally for fixed pitch). So when I pulled the front plug and looked inside past where that rear plug would go, I saw connecting rods. I turned the crankshaft and the rods moved out of the way. That's when I got the borescope idea. The VA-400 borescope is about 20" long and has an articulating head. I inserted the scope and when I got to where the rods were, I articulated the camera head upwards and viola- there was the cam! I then straightened the camera and inserted farther in until the next opening and articulated up again for the next set of lobes. I then went farther back yet (the whole length of the borescope was inside, including the handle stuffed inside the snout of the crank) and was able to see the last set of lobes.
If I ever get the chance to do this again I will certainly document better. Better yet if someone has an engine apart with the case halves open that would be a great tutorial.
Here’s more pictures with and without the rear plug in place. Also the very last lobe. You can see the split of the two rear case halves.
This video has a good camera angle to visualize how the borescope was routed:
https://www.youtube.com/watch?v=_49xL9oFLa8
Removing the prop, and maybe the crankshaft plug, will require a couple of hours work... but the idea is absolutely brilliant
And far better than pulling jugs or the oil pan...
PS
Never too old to learn
This cross section is good for the inspection understanding, but the mains have a drilled passage that feeds oil to the rods. This is typically fed with a center groove in the bearing. With lightening holes, the cross drilled passage can be at an angle to miss the lightening hole, but there in the center main bearing is a pesky hole into the lightening bore. What's that?? Some designs use a plug in there to allow oil distribution by sealing the bore, which is fine, but the design of it matters. It could be a dog-bone sleeve pressed in allowing the borescope to pass. Can anyone confirm that aspect of this design? Rocketbob?
Using this method one can't get a good look at tappet faces so its of very limited usefulness. Pulling the spinner and prop and plug, getting a new plug and installing it is more work than pulling a cylinder.
with all due respect Bob, kindly allow me to partly disagree...
Swiss story:
Many moons ago, we had an accident, 3 people lost their lives following a crash that occurred in the initial climb. The enquiry board cited partial power delivered by the engine due to badly worn cams as one of the causes, the report, in English language: https://www.sust.admin.ch/inhalte/AV-berichte/2160_e.pdf
As a follow-up, the Swiss FOCA (Fed Office for Civil Aviation) implemented TBO as rule making, e.g. the recommendation of 12 years became a mandatory engine overhaul. Unless you provided the authority with an additional maintenance program, and a one time (repetitive in fact, since it was supposed to be done every 6 years) inspection of the camshaft. This was done by pulling 2 cylinders, and, using a mirror, inspect the cams.
I owned a Falco at the time, and the removal of the cowl, the baffles, relevant ignition leads and spark plugs, pulling and reinstalling the jugs, took the better part of 2 days. With all the associated risks, as detailed many times by Mike Busch.
Removing and installing spinner/prop and eventually the plug, could probably be achieved in 1/2 day or less, and with less risks. As you state, an inspection of the tappet faces seems difficult.
Swiss story epilogue: hundreds of engines were inspected. AFAIK, only a handful were found with a damaged crankshaft, and this lead to the FOCA to drop the one time inspection.
Just surprised that nobody ever mentioned this method of inspection at the time, and I for one wasn't aware of it until this thread came into being.