Can one high oil pressure reading forever alter your engine? Mike, Paul, and Colleen answer this question, plus the quirks of the O-470, compression test redemption, and repairman certificates.

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Full notes below:

Everett is wondering if his oil pressure is forever altered. He has a Piper Colt with an O-235. The pressure used to be 75 psi, and on a flight the oil temp spiked and the pressured went up to 85 psi. Even after cylinder work, the temperature and pressure have remained high. Paul starts by asking if he’s sure the indications are correct. They suspect a blockage somewhere, although there’s no oil cooler on the O-235. They suggest getting a manual to check for the engine’s entire oil pathway and follow it to see if he can find a blockage.

Randall wants to know if the hosts are too hard on compression tests. He asks whether they hold any value. Mike said there’s no harm in doing compression tests, but that one should never change or overhaul a cylinder with compression numbers alone. Knowing where the air is escaping does offer some value, they say. There’s not much you can discover on a compression test that you wouldn’t discover on a borescope inspection that impacts safety of flight, Paul said.

Manuel asks how EGT and fuel flow relate on his Cessna 180. He’s seeing a spike in EGTs before they come down again on takeoff. The low compression O-470 will have higher EGTs, especially on takeoff. Mike said Manuel's engine monitor is configured for a carbureted engine, and thus puts a big time delay and smoothing function on the fuel flow. Without the smoothing, the fuel flow would wobble up and down often, making it hard to read. That’s why fuel flow indications rise so slowly after adding takeoff power. And bu slowly adding power, Manuel is delaying the addition of the enrichment function of the carb, which is why he’s seeing a delay for the EGTs coming down.

Marty is trying to understand repairman certification limitations. He’s done some work on his prop, magnetos, and so on, and he wants to make sure it’s all been legal. Mike said as he understands it, you basically have unlimited authority to do what you want on your airplane. The common sense rule applies, which is to get a demo or some instruction before you do it for the first time.