harsh tymes s13

i'll try and explain this the best i can. three different techs with three different timing guns have encountered the same out come. whenever they go to set and adjust timing. the car is telling them that 15 degrees is damn near turning the CAS fully counter clockwise. i had problems while it was set like that. the motor over haeated and ran like shit. so i adjusted the CAS after pulling over on the side of the road until the bolt was in the middle of the slot by eye balling it. the motor ran better and didnt over heat. but while in that position the timing guns are reading that the timing is 30 degrees. im using the loop in the back of the valve cover to hook into. the swap is an sr20det redtop in a 1990 240sx.