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C-85 Eng oil temp and pressure


Well-Known Member
Jun 2, 2005
Reaction score
Recently replace the A-65 with a C-85 on my Clipped wing Cub.

All is great except the oil pressure at running temperature at an idle.

First I must say I built up the motor and while I inspected the oil pump and gears I guess in retrospect I could have done a better job on the pump inspection. Suffice it to say there was nothing glaringly wrong with the pump galley, gears and cover.

I'm running 100w mineral oil and at cruise RPM of 2350 oil temperatures will normally level out at about 190°. This is well within the limit of 225° for a C-85 but much higher than my A-65 ever got. I'm running the same cooling baffles that where on my A-65

The problem is that with the oil temperature at 190° at an idle the oil pressure drops to 0 psi or nearly so. Granted minimum oil pressure is 10 psi which the motor will do if I keep the RPM at at least 800 rpm. 800 RPM is a bit to high for a CUB. Otherwise for the most part the oil pressure is in the green or higher at flying RPM.

I have checked both the oil pressure and temperature gages and am reasonably sure of their accuracy.

When the oil temperature is cooler say 170° or less oil pressure is sufficient and within specifications at all RPM ranges.

While the oil temperature is well within the max limit I'm not sure if I have an oil/engine temp problem or a oil pump problem.

So here are a few questions for those running a C-85.

1. Are you running the same eyebrow baffles as the A-65 or have you made larger baffles? (I seem to remember hearing this somewhere)

2. What oil weight are you running and what temperature are you seeing. What was the OAT and at what RPM will generate this temperature? (I know 80w is all that is called for per the manual but oil pressure is REALLY bad with this oil)

3. Any other suggestions before I tear down the engine for a different rear case a pump gears.:( :( :( :(

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