I realized I had misunderstood what I heard. I do not think this question any longer holds value and would cancel if I knew how.


I think she has participated in overhauls. She is very familiar with auto engines. I just think this time she overstated or over thought what could happen without really thinking the practical side of a few extra seconds and how lean cruise would probably burn stuff off it any was to actually appear. I do not want to question her skill and integrity; I believe she is a great instructor. I just think this one time there is more (or I misunderstood her) and am wondering if there is any hitory of this as a problem.


Recent discussion with my instructor resulted in something I do not understand. I get what she meant, but in my over-analyzing the topic...
During mag check, I switch to right to observe the drop and then check oil temp and pressure, and then check EGT/CHT (I have monitors on each cylinder). Then I return to both and let the engine settle (5 seconds or so) and then switch left to repeat the process.
The comment was made after I hesitated for both left and right in order to check ammeter and vacuum. There is no need to check ammeter and vaccum since they are not affected by mags. I agree.
But also stated that the extra few seconds is possibly detrimental to the engine because the unburned fuel could cause carbon build-up.
My observation: if unburned fuel could cause carbon during mag check, would it have noticeable impact when I switch to the other side. I feel that a few seconds makes no noticeable difference and the next runup would pass/fail mag check and I would burn off the excess carbon. It feels chicken and egg.


GARY PALMER replied to the topic 'C172M 180hp AirPlains conversion runs HOT' in the forum. 7 months ago

Given your earlier comment, we know your oil cooler is mounted on the firewall? And there is a scat tube (probably 3 inch) which connects from the baffle to the oil cooler. Where do you have the opening in the baffle which you closed. Mine is in the upper corner behind the #3 cylinder, is that where yours is too?

I am amazed that by covering the oil cooler air intake you actually saw cooler temps. Was that due to the cooler daytime temp or the better airflow over the 1 and 2 cylinders.

If you are in an experimenting state of mind, I was thinking about a small curved baffle mounted on the upper cowling which diverts some air flow down between the cylinders. I just have a few problems trying this: 1) I am NOT an A&P and unable to craft such an appliance, and 2) I am not an A&P and regardless of what i learn I am not sure I could do anything since the plane is certified.
But you bring an interesting question, would #1 and 3 be cooler with better air flow versus a diversion of air to the scat tub and oil cooler.

So I am thinking there is another approach (have I said I am NOT and A&P?). Instead of mounting our oil coolers on the firewall, what about a baffle mount? It would force more air flow to remain inside the baffle compartment and would still give good airflow over the oil cooler. Anyone have insight on that approach?


GARY PALMER replied to the topic 'C172M 180hp AirPlains conversion runs HOT' in the forum. 8 months ago

I have a 172M, the 180 HP Air Plains conversion, and hot #1 and #3 cylinders. I replaced the cylinders about 1.5 years ago because the prior owner ran it hot and my oil consumption just kept getting worse. Turns out my oil rings were shot. Now I have new steel cylinders (replaced the chrome things which I cannot remember right now). I also replaced the baffles using the new baffle kit from Air Plains, but that was before the cylinders.

My oil cooler was refurbished this year and that has helped a little.
My oil cooler is mounted on the firewall and the scat tube was replaced 2 months ago, the old one was worn and not forming smooth curves.
I spoke to Air Plains and they had a baffle mod which helped #1 and #3 by lowering the baffle height in front of #1.
Last oil change I notice a poor seal between the cooler and the scat hose (the flange) and plugged that.
I used to have plug base o-ring type temp sensors which are known to be hot, I replaced them with bayonet base screwed into the receptacle in the engine block.

I spoke to Lycoming and they said:
"The maximum cylinder head temperature for the O-360-A4M at the bayonet location is 500°F. For maximum service life, cylinder head temperatures should be maintained below 435°F during high performance cruise operation and below 400°F for economy cruise powers.

As aircraft speeds are typically lower and engine power settings are typically higher in a takeoff / climb configuration than a cruise configuration, higher temperatures may be encountered during takeoff / climb. Higher power settings generally equate to higher engine temperatures, and less cooling airflow will also contribute.

While I am not intimately familiar with the Airplains STC for the 180 HP conversion, the oil cooler would most likely have been stock equipment (although the STC might change it), even with the O-320 that the 172M model was originally equipped with. However, increasing oil cooler capacity or efficiency will most likely not have a large impact on the CHTs.

Some important aspects to consider are the fuel/air mixture being delivered and the amount of cooling airflow being delivered, as these will have the most effect. Ensuring that the carburetor is the correct setting for the application, and that there are no induction air leaks that will lean out the mixture even further are two items that can be evaluated. Airframe baffles and seals should be in the best condition possible, and the relative fit between these components and the cowling is extremely important as well. Even a number of seemingly small leaks or gaps may have a significant effect."

If I do more it will be to put the cooler back on the baffle to remove the scat tube, other than that I am watching this forum for suggestions.


GPALMER thanked STEVE ELLS in topic High Oil Pressure 3 years ago
GARY PALMER created a new topic ' High Oil Pressure' in the forum. 3 years ago

When everything is off my Oil Pressure guage shows something above zero. When engine running it is...


GARY PALMER replied to the topic 'GARMIN GDL-69 Datalink Weather Receiver For Sale' in the forum. 3 years ago

To JWBradley, I am faced with the exact same issue. My GDL-69A (with 530W/430) does NOT have a...


GARY PALMER shared 5 photos in the Catalina album 4 years ago

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GARY PALMER created a new topic ' Nav lights for sale' in the forum. 4 years ago

I have left and right (red and green) nav lights from my 1975 C172M. The bulbs and lenses are in...