Need help from the experts.

Weird, pero bakit nangyayari na naiiba ang timing ng ride ko when you rev it up or go on highspeed driving?

Napa tune up ko na and the timing was adjusted to 10 then when I went to Pampanga hataw ako 100kph to 140 kph. Pag dating ko dun tumotope na pag arangkada and then maingay sya. I had the timing read and it was way past 10 degrees.

I experienced this twice already.

Hmmm... what could be wrong?

The subject ride is a 1991 corolla 1.6.