Ideal cht

[tazin river]

Hey 180 drivers!

What do you try to keep your cht at? Mine appears to hover around
350 on floats....

Is this ok?

Cheers

[ahramin]

I assume we are talking about cruise. 350°F is a fine number, anything under 380 is ok. Is that on all six cylinders or just one? Threaded probe or spark plug gasket probe? What's it like in the climb?

[Big Pistons Forever]

Yup 380 Max is a good rule of thumb

[iflyforpie]

200F min for anything above 1100 RPM on the ground

300F min for anything in flight (low power let downs, etc).

Target of 380F in climb and cruise.

Nothing above 400F.

Redline 460F (six cylinder normally aspirated direct drive TCM engines)

[ahramin]

Where do you get the 300F min from ifly?

[SuperchargedRS]

Flying a 185 amphib with a 520

Nothing over 380 in the climb, nothing over 350 cruise.

Check your baffles and there is also the cowl louver STC and cowl lip if needed.

[tazin river]

Thanks folks

At cruise, do you guys close the cowl flap at all between 300 and 350? When do you start closing it under normal cruising condition? Is 350 what you try to keep the temp at with the o-470 continental?

[SuperchargedRS]

Ideally I'd like them closed all the time, less stuff hanging in the wind.

But it's like the zipper on your coat, zip it up when it's cold, but if you start getting hot you unzip right?

As long as I'm under 350 on the hottest jug I try to keep them as closed as I can.

[Big Pistons Forever]

There are some excellent references on line. I recommend the Lycoming Flyer key reprints.

Here is a quote from that document

In our many years of
building engines, the engines have benefited during
continuous operation by keeping CHT below 400 F in
order to achieve best life and wear of the powerplant

I also found a copy of the Continental IO 520 Operators Manual on line. This engine model is similar to the one found in the OP's airplane. It's only reference to max cylinder temp is a do not exceed 460 deg F although, like the lycoming flyer it also recommends keeping cylinder temp well below the max value


It also has this note

Do not permit cylinder temperature to drop below 300 Deg F. for
periods exceeding five (5) minutes.

I would hazard a guess that the max 380 F CHT target has become a generalized best practice as it would allow for some gauge error (under reading of CHT) and will ensure the engine never gets close to the max permitted values which both manufacturers say contributes to reduced cylinder life.