what is this??

[W.J.Langholz]

Brad

So at 6000 ft @ 2500 rpm you would be leaning?

W.

[Bruce Fenstermacher]

Not to answer for Brad but I would be leaning. In fact regardless of the altitude I try to remember to lean. By the book you lean till a decrease in rpm then richen back to the peak rpm. I have rarily done this exact procedure.

Through experience doing the book procedure I know that pulling the mixture about an inch and a quarter to an inch and a half is peak rpm. So I pull the mixture to about an inch. I know the engine is running leaner because I can see a rise in my single point egt but I know it is well rich of peak.

For the most part my plugs and exhuast pipes look fine and stuck valves have been few but I did just have one after about 300 hours.

I'm thinking of going back to the book leaning procedure specially on longer flights and reducing my rpm significantly only to reduce my fuel burn from the 11.1 gph I just got on my convention trip. But that is another study altogether outside this threads topic.

[W.J.Langholz]

So...........

What is the optimum head temp on a o-300 for peak performance and how long do you need to run it there and not get a hole in the top of your cylindar OR a stuck valve?

With out getting to sophisticated on this subject and (I am certainly no expert on the o-300) I did read the AOPA article on lean of peak, I would venture to say that most o-300's are babied too much and not run anymore at which they first were designed too do. Reminds me of a friend of mine that has a 57 Chev with a stroked out 350 and a 750 double pumper and all he does is gets it out and putts around town and wonders why it loads up on him.

W.

[hilltop170]

W.
I can't speak for all O-300-D engines but the one on my plane ran 1750 hours before it was overhauled. I put 1100 of those hours on it and the guy I sold it to ran it like I did for the 400 hours he had it. I consistently ran it at 2450 rpm and measured 7.2gph between fillups and followed the book leaning procedure Bruce described above and leaned at all altitudes. In that time, I used every kind of gas that was available, 80/87, leaded regular, 100/130, unleaded regular, and 100LL. I never had a stuck valve and I never used any snake oil in the gas. There were a couple of jug repairs in the 1750 hours such as one broken ring and two cracked cylinders around the exhaust valve but nothing such as burned valves or pistons. I had no idea what the cylinder head temps were. When I had the engine torn down, it was running fine and making no metal. The cylinders all had above 65/80 compression.

So I don't think you can hurt the O-300-D engine by running it at 2450 rpm and aggresively leaning. I'm running the newly overhauled engine the same way on 100LL. You regularly see 170s and 172s for sale with high time engines so I don't think my experience is uncommon.

In the picture, we're cruising at 8000', and the engine monitor is set on cylinder #2 because it has the highest CHT and EGT as seen in the digital readout below the lighted bars. The EGTs and CHTs are fairly even and in the normal range. You can't see the fuel flow but it was around 7.5gph. Good baffles and baffle seals are the key to maintaining even CHTs.

IMG_4401_1.JPG

[GAHorn]

Dubya, ... Richard's words are music to my ears. I agree completely with his comments.
Use the book procedure, cruise at 2450 RPM (lean over to look at the gauge to get rid of parallax...and I'll bet you'll notice it LOOKS like 2500 from the pilot's seat if your tach is original.)

At t ypical cruising altitudes 2450 is about 65% or less and you cannot hurt an engine running it lean at/below 65%. BUT.... your comments regarding Lean/of/Peak are not applicable to these C145/O300 engines. Their carburetion/induction systems are not sufficiently accurate to utilize such techniques, regardless of instrumentation, in my opinion. Use the book technique: Set power, lean to max rpm, continue to lean until FIRST sign of RPM-loss, then En-Richen back to MAX RPM and leave it there.

[W.J.Langholz]

Richard

Nice picture....wish I had some of that nice sh## in my plane. Yes you are correct baffling is very important I re did mine shortly after purchase. My engine is at 1700+ hours also 3 new ECi jugs and 3 normal ones. Burn 87 oct 50/50 every other tank.

George

Where ya been on vacation? I had to do something to get this forum cranked up so I picked this topic. And you are correct I do have and old style tach and when you lean over it is at 2450rpm...You are a smart man.

Now as soon as I say this I'm a going to ginx myself and end up with a stuck valve tomorrow...but.... and oh by the way when I get to 2450, in cruse, I do pull back slowly on the mix until a sputter then 2 cranks back in....I still would like to know, on the planes that end up with stuck valves, how they are flown on a regular basis. Do they get a chance to get warmed up good and run hard once in awhile.Are the carbs set correctly? I watch my CHT alot and you can really cool it down on cruse in full rich. Sometimes on a really hot day I do that, and I would say that I burn more fuel than I should at that point, but I don't believe I'm coking up the valves to the point of getting a stuck valve either. Maybe I shouldn't worry about the CHT because it never gets to the point of being too high but the oil temp sure likes to get close on those days above 92 degrees, and as the CHT comes down, a little later so does the oil temp. I seen some cylinders with some nice holes burned into them by running to lean also.

Richard, sounds like you have played with this some, and you have all that nice STUFF in your plane, where is your normal operating CHT run and where does your oil temp run "lean of peak" and is that @ 7 gals/hr?



W.

[Brad Brady]

W,
What Bruce, Richard, and George said........Brad....... Well I'm editing my post ......it seems that we we're writing at the same time.....After reading your last post....I got thinking "are we on the same page" to put what I was trying to get accost ....is .....my airport is at 640 msl...so if I have a density altitude of 3500 FT. I run the engine up to about 2300 RPM and lean to about 2350 or so....until I get a rough run...then back down to smooth...I now, know that I have peek RPM for that take off.....and at full throttle....(about 2500) I also have enriched the mixture to the point that I don't have to worry about overheating the cylinders......Brad

[hilltop170]

Richard, sounds like you have played with this some, and you have all that nice STUFF in your plane, where is your normal operating CHT run and where does your oil temp run "lean of peak" and is that @ 7 gals/hr?

W.

W.
I didn't have that neat stuff the first 1100 hours in this airplane, just the last 100 hours. I only had a 6-position EGT I rigged up myself that worked very well with a single analog gauge and rotary switch (before I was aware of field approvals, STCs, 337s, etc). I always ran the engine at 2450rpm and leaned until stumble then enriched until smooth. The fuel flow was consistently 7.2 to 7.5gph calculated by dividing total gal at fill-up by tach time. I still run it that way but can now monitor all six EGT and CHT, oil temp, and fuel flow. The CHTs typically run 325-375°F and the oil temp runs 200°- 225°F in cruise in the summer. The plane is in Texas so it sometimes flies in hot weather, but not often. The fuel flow still runs between 7 and 8 gph. I'm not sure I can get the mixture of all cylinders to run lean of peak, that is something to check out though, I have never really looked for it on the engine monitor. The mixture distribution between cylinders is bad enough that I think the first cylinder stumbles before the rest of them can go lean of peak. I re-lean at each power and altitude change. With valve rotators on the exhaust valves and leaning aggressively, I'll be surprised if I get any sticking valves.

[W.J.Langholz]

I had a elderly gentleman told me the other day that the way he solves his sticky valve concerns is, every so often on run up he will flip to one mag lean it out , run it up to1800 -2000 rpm's let it bark stumble spit and sputter for awhile then he'll do it on the other mag. Claims it cleans his plugs too.......wonder if that fits the term "Getting the Carbon out"

At the end of the day if i was error on the side of lean of peak vs too rich it would be better in the long run, atleast until I get some of those neat gauges in my plane. I would suffice to say, I still think alot of the sticky valve issue goes to how that plane is operated daily....and just because it is becoming a collector-classic doesn't mean it should be coddled.



W.

[Bruce Fenstermacher]

You shouldn't cuddle the engine. Run it as it was designed. Unfortunately it was designed for 80 octane and no lead. I think I would disregard your old gentleman friends advice. Running your engine at the just rich of peak mixture including when taxiing is the best you can do to eliminate the lead deposits out the exhaust.

I'm not sure how it is some people seem to get away without any valve sticking. When I discover definitely without a doubt I'll be sure to post it here. Running at the optimum mixture helps and I personally believe that MMO in the gas helps to lube the valves and keep them moving. Probably a proper cool down period before shut down helps as well.

But I don't lean to the optimum on a regular basis and I can't remember the last time I used MMO in the 170 and I never purposely have a cool down period before I shut down.

[W.J.Langholz]

But I don't lean to the optimum on a regular basis and I can't remember the last time I used MMO in the 170 and I never purposely have a cool down period before I shut down.

Rat Fink.jpg

Big Daddy says that's where your oil goes.....lube the valves

W.

[hilltop170]

One of my elderly friends claims the best procedure for parking the plane is to stop at the fuel pump with the nose into the wind, get gas, then taxi to the tiedown. He claims the shutdown, restart, and slow taxi allows the engine to cool off more uniformly, eliminating hot spots that could warp valves, crack cylinders, etc. He also claims the cooler engine allows the fresh bath of cooler oil to stay up in the engine longer lubricating for the next start and lowering corrosion rates. I haven't seen any of that in an owner's handbook anywhere but it may have some merit.

[johnsunday]

My pipes are cut with a fore-to-aft slant...looks like it should produce a positive pressure on the exhaust system....Only the left stack leaves the gray residue....go figure...

John

N2786C, Ratty ole Alaska Bush Plane

[Bruce Fenstermacher]

John this is very common. Both the cut and only one side leaving residue.

[170C]

My IA encourages aggressive leaning during taxiing. Another IA suggests that at shutdown one should pull the mixture out and push the throttle in at the same time. His theory is that that helps purge the fuel from around the spark plugs. Does it work? I will see the next time I pull the plugs.