O-235C1 CHT 455?

[PA-16]

My sweet 16 came with a CHT gage but it went belly up last year, not required so wasnt too concerned. I bought a used one on ebay for 20 bucks an EI digital unit, using the same spark plug washer probe the old westach CHT used it was showing 455 during cruise.. anyone else seen that high CHT on a spark plug washer type probe?

 

[Smokey]

Aviation spark plugs have a Heat range. With less transfer area the nose core of the plug can get as hot as 1200 degrees. The idea is to reduce fouling. With a projected nose core plug like the 37 BY used on the O 235 it can get pretty hot! That is why spark plug gaskets read 50 degrees higher. It is attached around the plug. So CHT is 405. Is there a cold junction adjustment at the gage?

Todd

 

[PA-16]

Thanks, I found another analog westach gauge and tried it, waa between 325 and 350 at cruise, but reading through the notes on their website I found that they cal them to show the difference between a set point of 75°f and the cht, I need more coffee to figure out why they do that...not sure how accurate any CHT gauge is now after reading that, heres the link to the westach doc that talks about the calibration or fixed temp setting https://1529df4b-92d9-45d7-8a55-ef7...d/1529df_382742a3eb3046a6acf883179ad4614f.pdf

 

[Smokey]

Calibration. uncut length of the wires. position of the probe in the exhaust. cold junction set to verifiable source.