Inliners International Forums General Discussion Blown and Injected Knock Sensor

Isn't there a stock 250 knock sensor on the 77 and above Chevy 250 that can be used? The thread I found on knock sensors is talking about going to a V8 sensor. Is the V8 sensor better, or was there no viable knock sensor system on the 250 that I could use?

Knock sensor thread:
Knock Sensors

As that thread's first post talks about, knock sensors work on frequency, so you want one that operates at a frequency range you except to operate at.

I installed one in my Buick 455 V8 from an early 90's Chevy truck figuring low rpm loads, etc. I drilled out the existing water drain plug threads in the block and re-tapped it for a larger thread that matched the knock sensor. Same could be done on the 250. The early EFI Buick 3.8's installed them in a hole on the flat spot where the transmission bellhousing bolts to behind the intake. I don't think Chevy's have a flat spot there though.

I never got the one on my Buick to work properly because of valve train noise, but I think the MegaSquirt software has gotten better to where it will only listen to the sensor during certain sections of crank rotation to listen around valve train noise, but I haven't re-tried it though the sensor is still there.

Roger that, but do you have any info on the stock 250 block knock sensors?

I'm not changing the bore, stroke, cam, etc and want to go with something already purpose built for the 250.

We are running the stock knock sensors on a Vortc 4200 using MS3-PRO, they work great, although I don't know a lot about them. I had a hole cut in the inner fender panel for the wastegate tube to exit and it was banging against the inner fender panel and setting off the knock sensor. Scott Clark said it was not in the range where detonation would be, he knew right off that it was something else.

Ah! Yes mechanical contact can give false positives. I used to run into that on GE LM2500 and Rolls Royce 501 gas turbines with the accelerometer leads getting loose and shaking about.

Our early pickups used the piezoelectric crystals like the knock sensors. We had our calibration range to hit just like the engine block sensors.