I am thinking of adding a knock sensor. I have read that it can be difficult to detect slight detonation.

After reading the blurb regarding ring gap for KBs hypereutectic pistons the part where they warn that if the engine gets into detonation even with a huge ring gap of 0.060 the pistons can hang up.

A Ford knock sensor works off a 2.5 volt carrier signal and the knock sensor uses the carrier voltage kinda like an antenna for the RF signal it produces and transmits, sorta like a MAP sensor.

Therefore, you can't read the signal with a voltmeter because it will only detect the 2.5 volt carrier signal and not the RF signal that the computer is really monitoring.

There are three wires to that system. The supply voltage is VREF, 5.0v (+ - 0.3) and the Signal Return, which is basically the ground. The third wire is the Knock sensor RF signal transmitting on the 2.5 carrier voltage.

I will try to find one, next trip to the bone yard

I don't suppose you remember what color is what for the 3 wires???

What kind of cars and trucks are they used on?

What does the sensor look like?

Where are they located?

The VREF wire is orange, the Signal Return is black w/white stripe. and I don't remember the knock sensor color. However, the colors change in the late 90's early 2000's.

Knock sensors are used on all the Fords cars and trucks up to early 2000's, although I quite working on cars after that.