From what I've seen, these engines can easily go almost twice TBO if they are taken care of exceptionally well. Most of this care is in flight, not in the shop from what I've read (Mike Busch et al).

I would expect that most engines could go well past TBO if they all received excellent care.

.

Just for further discussion...

I can't recall anyone ever mentioning camshaft break-in during discussions and aircraft engine break-in and I find that interesting. What really made me start thinking about it was earlier this summer I replaced the camshaft in my boat which has an old Ford 351w with a flat tappet cam. This occurred while I was reading my IO360 overhaul manual and prepping for that job.

There is a very specific procedure for breaking in a new cam in a flat tappet automotive engine but aircraft engine break-in procedures don't seem to mention anything about it. In fact, the procedure in my IO360 manual instructs the operator to do things that cam manufacturers caution you to avoid doing after installing a new cam. Improper cam break-in can result in a flattened lob in a matter of minutes. I can't imagine that our 1940s engine designs are more advanced than that of a 1960s era automotive V8.

This oil pressure lubed cam STC would certainly help avoid the damage that can easily occur during cam/lifer break-in.

Mountain Doctor wrote:Use Camguard and fly as often as possible.

I have read that multiviscocisy oils protect better against corrosion but I can't recall the source. May have been Mike Busch.

I've read the same about MV oils, I have also read the exact opposite - that it runs off sooner and straight weight sticks around longer on vertical surfaces. I use MV simply because I expect it to flow better than straight weight at low temps, and protect equally at operating temp. I run Camguard on top of that in the hopes that it + my dry climate will help an engine that isn't running real often. I am having lifters pulled this week during annual, so we'll see.

hotrod180 wrote:I'm reminded of the air taxi outfit that used to be on my airport.
Several C172's and a C206.
Every airplane flew every day.
They ran a number of engines to TBO with few problems,
using straight-weight Aeroshell W100 with no additives, no pre-heat, no spin-on filter.

No pre-heat concerns me, but it depends on the temps. They fly so often that the parts may be coated well enough to protect them even with a cold start, but unless you are literally only going hours between flights, I would still preheat if the ambient temp has allowed that engine to cold soak at or below freezing. Av oil, especially straight high weight, is like sludge when it's cold. Anything to get it moving sooner is going to be good.

I also don't know how well the cursory 15 minute hot air preheat the schools use actually works. The external metal is certainly warm, but the 6-10qt of goop in the sump is most definitely not. I think it takes a good bit longer with consistent heat to really get it where it needs to be. I have an oil pan heater on mine, and will probably add the cylinder heaters this winter, along with a remote plug I can hit from my house a few hours before I expect to fly.

whee wrote:This oil pressure lubed cam STC would certainly help avoid the damage that can easily occur during cam/lifer break-in.

Hmm, true. But, if it were that large of a problem, wouldn't we have new cams grinding to death as a regular thing? I am fortunately not well versed in personal break-in experience, but I know the mfr's do not want to see engines coming back because of a bad instruction.

whee wrote:. ...There is a very specific procedure for breaking in a new cam in a flat tappet automotive engine....In fact, the procedure in my IO360 manual instructs the operator to do things that cam manufacturers caution you to avoid doing after installing a new cam. Improper cam break-in can result in a flattened lob in a matter of minutes......

Can you elaborate please?

hotrod180 wrote:

whee wrote:. ...There is a very specific procedure for breaking in a new cam in a flat tappet automotive engine....In fact, the procedure in my IO360 manual instructs the operator to do things that cam manufacturers caution you to avoid doing after installing a new cam. Improper cam break-in can result in a flattened lob in a matter of minutes......

Can you elaborate please?

I don't have the IO360 initial run procedure in front of me be in goes something like this:
1. Start and idle for 15min. Shut down and check for leaks.
2. Start and run at 1500 rpm for 5 min. Shut down and check for leaks.
3. Start and run at higher rpm (mag check, prop and WOT check). Shut down and check for leaks.
3 Start and fly for 1 hour keeping power above 75%.

Here is the relevant step that came with my V8 cam:
Start the engine and immediately bring to 3,000 rpm. Timing should be adjusted, as closely as possible, to reduce excessive heat or load during break-in. Get the engine running fairly smoothly and vary the engine speed from 1500-3000 RPM in a slow, to moderate, acceleration/deceleration cycle. During this time, be sure to check for any leaks and check out any unusual noises. If something doesn’t sound right, shut the engine off and check out the source of the noise. Upon restart, resume the high idle speed cycling. Continue the varying “break-in” speed for 20–30 minutes. This is necessary to provide proper lifter rotation to properly mate each lifter to its lobe. Should the engine need to be shut down for any reason, upon re-start it should be immediately brought back to 3000 rpm and the break-in continued for a total run time of 20–30 minutes

The instructions also call for a break-in oil with a high zinc content and caution against unnecessary shutdowns.

I realize we can't really run our aircraft engines like this but the stark difference in procedures is interesting. The valve trains in both engines function the same and both are assembled with moly grease so I was expecting the IO360 overhaul manual to say something about cam/lifter break-in.

I've always wondered why car & motorcycles engines recommended break-in is "run it easy",
while with airplane engines it's "run it hard".

hotrod180 wrote:I've always wondered why car & motorcycles engines recommended break-in is "run it easy",
while with airplane engines it's "run it hard".

Bad advice from the car and motorcycle crowd. Airplane engine break in procedures are way better for sealing rings.

hotrod180 wrote:I've always wondered why car & motorcycles engines recommended break-in is "run it easy",
while with airplane engines it's "run it hard".

Possibly something to do with tolerances in a liquid-cooled engine, compared to an air-cooled engine. I don't know.

Battson wrote:

hotrod180 wrote:I've always wondered why car & motorcycles engines recommended break-in is "run it easy",
while with airplane engines it's "run it hard".

Possibly something to do with tolerances in a liquid-cooled engine, compared to an air-cooled engine. I don't know.

Also possibly because cars and motorcycles are not designed to operate at full power, red line rpm, while aircraft engines are.