Front baffles on C-145-2

[N2782C]

My # 6 & 5 cylinders run a very cool CHT...about 80 degrees cooler than the rest of the cylinders. I noticed that the early C-172's had baffles in front of the # 6 & 5 cylinders with basically the same engine. Is there any way to get those baffles, or to make them and still be legal?

Thanks.

[jrenwick]

I've noticed the same thing on my '55 B-model. I discussed it with Jim "Monty the answer man" Montague (on the Swift web site) once, and he said he didn't think running cool would ever hurt a cylinder on the small Continentals. My J3 flies all winter with its cylinders out in the breeze, and it's never seemed to complain.

John

[GAHorn]

The downdraft cooling system of our Cessnas is a somewhat different animal than the updraft cooling of the Swift. The reason Cessna installed the later front-baffles was to improve that downdraft airflow. Face it, an even-temperature on all cylinders is better than hot/cold areas. The blast of air at the front of the cylinders interferes with the airflow over-the-top and descending thru the intercylinder areas. In particular it creates a high-pressure area in the immediate underneath of the front cylinders and that creates a hot-spot regardless of the temperature where your gauge samples the cylinder.

I'm reminded of the time a mechanic pointed out that my 206 was missing a small baffle behind it's oil cooler and how that wasn't right. Looking at the area, it appeared that adding a baffle behind the oil cooler would BLOCK cooling air to the #5 cylinder. (Air flow thru the cooler would next enter the front fins of the cylinder. Installing the missing baffle would block that cooling air and direct it downward into the lower cowl. Another short baffle would also put a "cap" on the cylinder and definitely appeared it would reduce available air to that cylinder.) But I agreed to let him order them and install them. To my surprise both my CHT and my Oil Temps went down.

This might be another example of how far do you go into the project to satisfy yourself you have an "approved" status. Mfrs spend a lot of money and time testing engine baffles and the results are not always intuitive. Anything resembling "homemade" is likely to raise questions, so you might wish to stay with baffles from a mfr of approved baffles such as advertise in the 170 News.

[N2782C]

Thanks, George. I'll try calling one of the advertisers.