My 64 lemans 6 cyl has smoke coming from the valve cover breather to the air cleaner only when the a/c is on. Goes away when I shut the a/c off.A/c works fine.
Unless the engine overheats with the AC on, there is NO reason for this to be happening. I suspect excessive piston blowby OR a non functioning crankcase ventilating system. Good luck with it, and make a dry and wet compression test on the engine.
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