huttler

Where should I put the knock sensors on my LS3? The location on the attached image is too small for the original knock sensors. Are the newer style knock sensors compatible with the C5? What about an adapter. I found an image (attached) on the internet, but it gave no reference.

Eric D

The LS3 knock sensor attaches to the engine block between the side bolts for #3 and #4 mains. The sensor takes a through bolt to hold it in place. The LS1, LS2 and I believe the LS6 use different sensors than the LS3, LS7 and LS9.

Bill Curlee

Knock sensor placement and installation is critical. The sensor is tuned to that location and install method. Using an adaptor will change the way the sensor operates and will significantly change the way it reports back to the PCM. You may be expierencing knock but the sensor may not detect it due to being mounted in the adaptor.

Get the correct sensors and install them as per the service manual.

BC

VGLNTE1

I had to tap the bosses on th side of the block so they could fit. They are different thread types

huttler

I didn't give enough info in my first post. I'm installing an LS3 in my 99 C5. The knock sensors are not located underneath the valley cover on the LS3, and can't be installed there. The LS3 has an external location for the knock sensors. But the LS3 uses a new style knock sensor, and I can't install my original knock sensors in the new location because the mounting hole is small.

I'm not sure what to do. I've read of some people tapping the LS3 mounting holes to the proper size. But I don't want to modify this block since its new, unless I have no other option.

huttler

Alright, looks like that's the only option. Do you remember what size tap you used?

VGLNTE1

in my opinion, they are worthless anyway. (many dont agree) If you run a aggressive set up, they wont catch the problem till its to late anyway. They can only retard 8 degrees...ask me how my 346 knows

I just tapped mine. Thats why katech makes the adapters. They then fit in there, even with long tubes

VGLNTE1

I sure dont...lemme ask a buddy, I will get back to you

VGLNTE1

we dont remeber. was about a year or more ago. its either a M12x1.5 or M10x1.5....

finding the thread pattern of the knock sensor wont be hard to find

huttler

thx for the help, it should be easy to narrow down from here

VGLNTE1

how did it go?

huttler

I haven't done it yet; I've been unexpectedly busy with other things, hopefully tonight though.

I did get the tap, the correct one was the M10x1.5

aahrested

I am in the middle (actually almost finished) of doing the same thing, installing a new LS3 crate engine into my 98 c5. I just drilled those holes out larger, and tapped them. If you do not wish to do that, there are extra holes already drilled to the correct size that you can use. I would have used some of the existing holes but, they were in the way of my headers. The issue I am having now is how to mount the EVAP purge solenoid/EVAP vacuum switch tubing. Let me know how you do yours, however 98s and 99s are a little different but, on mine everything is in the way to mount that piece. I think mostly because of the different valve covers so, I would like to know how you handle that