Because they're designed to run on regular unleaded fuel. A knock sensor is really only necessary when you have an engine that takes a higher grade of fuel, to prevent damage from people putting in regular when it's supposed to take premium.

 

They were never really intended to push into the high performance realm for where knock typically occurred.

These engines were more intended to be workhorses, like in the F150 and Crown Vic. They're so far from knock conditions it wasn't even a concern.

Now when you look at the 99/01 Cobra or Mach 1, they do have knock sensors. They're running much higher compression and a different cam profile.

 

Thanks for the reply, I was thinking the same thing. That motor was design to be for a family sedan or taxi, "crown vic".We are pushing them way past there limits and have to tune the motors without them. I think things would be much better if they where there.

A friend of mine has a 97 cobra with a ysi blower on it. He had the intake off and I seen the knock sensors. Figured I'll start a tread about it.