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Question about cylinders ? I was lying on my back tiring to figure out how to install my air box when I noticed at the bottom of each cylinder behind the spark plug a threaded hole. Its quite deep but does not appear to go all the way through ( has a bottom ) Would I be right in thinking these are for CHT probes and if they are not used should I be putting a threaded plug in them?

Thanks

 

[mahlon_r]

Yes those are for cht probes. If you are not using them leave them alone.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."

 

[gmcjetpilot]

cht probe

If you do use cht probes be sure to get the ones that use these threaded wells. The other type is the spark plug ring or gasket type. They take the place of the spark plug gasket. Wire leads extending from these rings. They are well known for being inaccurate and Lycoming bases all CHT limits on the threaded wells, which is much better. Also as recommended by Lycoming do not exceed 400F for any normal operations. I highly recommend you get at least one cht, on the RV it is almost always #3, Back right. Regards George

 

[Rick6a]

...as recommended by Lycoming do not exceed 400F for any normal operations. I highly recommend you get at least one cht, on the RV it is almost always #3,...

With 17 hours on the Hobbs, I have been doing everything I can to get those CHT's lower. Probably a good thing because I really tweaked the baffling as much as I know how. My efforts did managed to reduce the temperatures somewhat, still, the CHT's remain in about the 404 degree range, with #3 running at 418. Finally, I referred to the official Lycoming Operator's Manual that was included with my new O-320-D1A. Page 3-11 says in part: For maximum service life of the engine, maintain cylinder head temperatures between 150F (66C.) and 435F (223.86C.) during continuous operation. The maximum cylinder head temperature is posted at 500 degrees. Hopefully, I will see the CHT's go down as the new engine settles in. It has been very warm since I started flying. Today, the OAT at 3500' was 84F. I'd like to get those CHT's down to the high 300's but if I read the manual correctly, I'm not abusing the engine.

Rick Galati RV-6A "Darla"