Gasket Compound

[wa4jr]

I thought it time to touch off another round of spirited conversation! Coming from the auto world, I am used to applying a thin coating of gasket compound to all gaskets with the exception of cylinder head gaskets. I find it comforting to see the slight ooozzz of compound from the sealing joint to indicate a good fit and seal. However....an A&P/IA told me that gasket compound was not used on aviation engines. Said that gasket sealer was not needed if the proper gasket was used, proper torque values used (if you can find them) and the sealing surface is in good condition. So what is the feeling of the group? I ask this in reference to my removing and reinstalling the rear accessory cover on my O-300A while changing to a B&C starter. I would think that non-hardening compound would be a good bonus for the accessory case, as I don't want to get everything on and find I have an oil leak that could have been prevented with the sparing application of gasket sealer in the assembly stage.

[cessna170bdriver]

John,

TCM's Service Information Letter SIL99-2B says to use K&W Copper Coat 1504-12 on the crankside side only of the C145/O300 accessory cover gasket. That particular K&W number is a brush-on available at some auto parts stores, but I couldn't find it locally here. I did find the spray can version locally, and worked well for me. (The guy behind the counter at Mojave Auto Parts says it's good for high temp applications, and a lot of his customers use it on head gaskets).

The SIL doesn't specifiy what, if anything, to use on the accessory cover side, but I used the Permatex Aviation Grade 3D, also available at auto stores. I used 3D everywhere the SIL didn't specify what to use, other than my AI suggested we install the mag gaskets dry to allow for adjustment. 9.5 hours and my only leak is that Jasco alternator I decided not to overhaul .

Miles