Knock Sensor/Block Drilling Advice

[cspetros]

I don't ask many questions, but I've come across something that I need some advice on. I've read the threads that discuss the block/knock sensor boss issue, but they are mostly "N/A block v. Turbo block differences" threads, and do not go into sufficient detail. Here goes:

I've gathered all parts needed for a N/A engine build for my '92 G-GS. I have discovered something that has halted progress for the moment, however.

The ECU in my G-GS came with a knock board installed (Yes, it's strange. This fact was discussed in ThIs thread.). The original block from the GS had a raised, tapped spot in which a knock sensor was installed:


The problem is that the block I am using for the engine build (not the original block) does not have this raised area:

(Actual picture of block; the area for the K.S. is not raised, with an unthreaded, shallow hole [instead of raised, and threaded])


I am asking for advice on what to do about this. Being that the engine is N/A, a knock sensor isn't 1st priority; on the other hand, if I leave the sensor unplugged, the ECU will revert to a set knocksum, and retard timing by default (I do not need an even slower car /ubbthreads/images/graemlins/grin.gif). I would rather not buy another ECU (this one has been recapped, and works great), and I would like to use this block, as I have already prepared it (cleaned, painted, freeze-plugs). I am not using the original block due to huge amounts of cylinder wear. The pictured block I am using is the original block from my N/A '90 G-GSX, and is in great condition.

Maybe it's possible to drill the block, even without the raised area? It does have a hole there, but I think drilling too much might puncture the water jacket. Or, maybe it's possible to "fool" the ECU somehow?

I would appreciate any suggestions/advice. Let me know if you need any more information.

 

[Struc]

Use the hole that is up near the top of the block behind cylinder #2.

When using a N/A block, that is the best place for the knock sensor. The 2.3l in 56/1000, which I purchased from blackhole on this board is a N/A block, and that's where the knock sensor is threaded in. It should be just as good as the other position.

 

[1990ggsxnj]

Ok, so Struc beat me to it while I was posting /ubbthreads/images/graemlins/hsugh.gif..but here it is anyways /ubbthreads/images/graemlins/grin.gif.
Might sound like a stupid question but is there another hole that can be tapped? I wouldn't tap the one near the water jacket as that is just a major pita to redo another block or have it repaired. Worst comes to worst, plug it in and leave it off if you are not concerned about it. What compression will you be running? If it's anything over 9:1 I would try to keep it and thread/use another hole.

 

[cspetros]

The compression ratio is 9.8:1, according to the service manual. The 1992 N/A DOHC models had a 10hp increase (145hp) over the prior models, which had a 9:1 ratio. I guess this is why it needs a knock sensor. In order to achieve this extra compression, the 1992 N/A models have different camshafts in the cylinder head to change the valve timing. I didn't realize this until tonight; I thought all N/A cams were alike.



Anyhow, you guys rock. I'll screw it into that hole that Struc suggested. This gives me peace of mind over some rigged setup. Much appreciative /ubbthreads/images/graemlins/smile.gif