Background 1. I am ignorant ish 70+ hr student, airplane owner. 2. Oil changed recently. 3. Com 1 was all static today, unusable. 4. 1974 C172 M I think I am getting close to checkride time for private. Today was supposed to be last mock checkride with CFI, get signature to test. I'm flying in to meet him, overfly the field, hear winds are 8G17, sock is erect, perpendicular to field. I am signed off for XW of 10, decide to come home. Immediately get a puff of grayish smoke in cockpit, I think electrical smell. Did not last long. I turned for RW right away, added flaps, slipped, 40 flaps, smooth landing. Trust me, I did not notice any winds... Mechanic to help troubleshoot. Did not fly it further. Where would you look? What is the seek and find algorithm for this? How and where does air come in from at bottom of windshield? Might it have been a drop of oil near a hot intake? What would you do?