Cessna 170/140 winter block off kit question

[DENNY]

Cold and waiting for IA to do annual so just some stuff to ponder. Boiling point changes with altitude. boiling-points-water-altitude-d_1344.html. So you may want to calibrate that water boil temp line after figuring out density altitude of your location on that day. Another point is put a pan of water on the stove at 160 degrees and it will evaporate, not as fast as 180 degrees but it will get there. I use a blocking plates in front of my rear mounted oil cooler to keep my oil temp up. Also run Cam Guard and change at 25 hours even with a filter.
DENNY

 

[Scott 2020]

A couple of years ago I wrote a piece about cooling for Vintage (attached)

It may seem counter intuitive but I would have a good look at the engine baffling, seals, and any other ducts or openings that might allow air to "leak" from the upper engine area. But, you say, we want heat in this case...

There should be static pressure in the upper engine area in flight. Baffles/seals missing and/or poorly fitted may reduce the static pressure to the point where there is no delta and so low or no air will flow into the cabin.

This will of course show up more, as the intake air is reduced by the winter kit.
S

 

[BC12D-4-85]

Cessna Skywagons have a set of forward facing air intakes on the rear fuselage. I asked and was told they were for adding cabin pressure and ventilation against potential CO from the exhaust. I assume the air captured moved forward.

Anyway, the heater system has two main air intakes. One under the oil cooler and maybe elsewhere depending on model, that feeds the heat muffs. They also have an external air door on the boot cowl to add cool air if desired, plus force more mixed heated air flow through the various cockpit vents, like the shield defroster. Without that external door open some, plain heated air had a hard time fighting differential cabin pressure when it was real cold. Like below -30F cold.

Gary

 

[dogone]

I have the 180 hp conversion in my 170b . I keep warm air in the engine compartment by restricting air exiting. I extended the bottom of cowl by about a foot. Brought temps up nicely in cold weather. I also added a two inch high lip on it for very cold weather. This also goes on or off with a few screws.

 

[Charlie Longley]

I flew in Barrow for a few years jn 185's, 207's, Navajo's and Twin Otters. We never used block off plates at all. But the company policy was to not fly the recips below -40. The Twin Otters got quite a bit of work.

 

[BC12D-4-85]

C-170B w/180 reminds me of a local A&P that flew one in winter. Engine ran cool so he blocked off one side of the cowl inlet with cardboard and duct tape. left the other half open. Said it helped. Later, unrelated perhaps, he lost a cylinder on floats and had to set it down just prior to freezup. A helicopter, snowshoes, and a chainsaw got it off the frozen lake. Lots of ways to do things as needed.

Gary

 

[mvivion]

I have the 180 hp conversion in my 170b . I keep warm air in the engine compartment by restricting air exiting. I extended the bottom of cowl by about a foot. Brought temps up nicely in cold weather. I also added a two inch high lip on it for very cold weather. This also goes on or off with a few screws.

I've always believed that controlling the exit air, as many larger aircraft have done with cowl flaps or some sort of restriction, is a much better plan than controlling inlet cooling air.

MTV

 

[TRDunn]

Once one starts modifying the OEM designed airflow through the engine compartment, one requires good feedback (data) from its effects on the engine. Typically, a fully probed temperature system for all cylinders provides this data. I ran stock Cessna winterization covers (aka block-off plates) for 15 winters in interior Alaska with a UBG-16 providing the data I deem a requirement for proper care and feeding. I ran my 0-470R to TBO twice (BJ overhauls in Palmer, yes, Bob has retired to the lower 48) and now on a third with the preponderance of operating hours in sub-zero temps. No cylinder replacements between overhauls. Our work required multiple climbs to 10-12K followed by descents to the surface. IMO the reduction of cooling flow to the engine is a requirement for this mission profile while operating in sub-zero temps. (Failure to reduce intake combustion air results in lean mixture as well)
As for cabin heat, its relative. The ram air is reduced by the winterization plates. Running with the cold air door partially open definitely helps but obviously reduces the temperature as it dilutes the heated air. When operating in colder than -20F I fitted an adapter I made into the right-hand floor outlet ahead of the doorpost and ran a piece of 2" SCAT (about 6') so the rear seat occupant could clear the side windows as when descending into colder temps (typical inversions) resulted in the windows frosting over on the inside. My self-induced no-go temp was -35F, however, the coldest I saw airborne was -45F letting down into the FortyMile drainage east of Fairbanks. It was not possible to keep the windows clear at that temp and the forward visibility was only through the little frost-free hole provided by the defroster. Not a hospitable operating environment and I did not linger.
I am just sharing my data ref cold weather engine care and feeding (well over 3000 hours on this one engine operating in mostly sub-zero temps with zero issues. This worked for my mission, yours may be different. Just providing a data point, no other agenda.
TR