VAF Forums - Normal CHTs - should I stop worrying?

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- - Normal CHTs - should I stop worrying? (https://vansairforce.net/community/showthread.php?t=159419)

Quote:

Originally Posted by JackinMichigan (Post 1252011)

The 178mph speed I was referring to is the maneuvering speed, or structural speed, not the top speed. .

Maneuvering and Vno are not the same thing. I think you meant just the latter.

Not a 540 (or cooling) expert, but my only concern is, as you mentioned, that if you are reaching 410 on climbout when OAT's are in the mid 30's, what will they be this summer when OAT's may be in the 80's or higher on climbout? Maybe not worth worrying about until it is further broken in, but they will certainly get higher as the days get hotter. In general, my CHT's tend to rise just about the same amount as the OAT (ie, if OAT goes up 40 degrees, so do CHTs).

Chris

What you are seeing is perfectly normal for an engine with only the few hours you have on it. Do as Dan describes and fix the rear baffle behind #5 and it will come down. Adjust the front air dams as required. You won?t see much of a significant drop until you have 40 plus hours on the engine and replace the mineral oil.
I wish mine were as cool as yours when I was doing my first flights.

Quote:

Originally Posted by Ralph Inkster (Post 1251969)

The advice I’ve always followed from old time mechanics (& shops) is to run an engine hard & hot during break in, between 380 & 400, to insure the rings seat and not glaze the cylinders. Lycoming red line is 500, I set a 450 no go limit, so even with 400 is well below any thing serious.
With slippery RV airframes this is hard to do so I leave all gear fairings off during break in, try to make the engine work as hard as is sensible.
Your running mid to low 350 temps seem conservative for a 10hr break in engine.

Dangerous advice. Definitely good to run them hard at break in to seat the rings, but not hot. I accidentally let my CHT's get into the mid-400's' for half a minute during the first hour and the cylinders glazed. The fresh cylinders are more susceptible to glazing before the rings seat and glazing is caused by heat. The material deposited (i.e. the "glaze") is coked oil.

Larry