I'll try not to be long winded so here goes. Here in Canada we have to go through the GM dealer where we purchased the engine. I spoke with the service manager and was advised that I would have to bring it in so they could hear the knocking and then tear it down to find the cause. I was not going to leave my car there under any circumstances. I went to an engine builder who came highly reccomended. I brought the car to him and he was able to hear the noise personally. I took the motor out and took it to the engine builder for teardown. I asked him to document everything. The results were thus: there was no sealant on the rocker arm studs so oil was getting past the threads and into the cylinder (the upper cylinders were coated with an oily sooty deposit). The piston to wall clearance was found to be .0025" - .0030" skirt clearance (specs call for .001"). The pistons have a coated skirt and 4 of the 8 pistons showed signs of scuffing (including the #8 piston which is the one I determined to be knocking). This info was sent to the service manager who in turn sent it to the GM rep. Well GM authorized and paid for (fully) to have my motor rebuilt by the engine builder including the $700 dyno fee. I was pleasantly surprised, I thought that I would have a fight on my hands. They did offer to replace it with another crate motor but I told them that I did not want to go through this again and neither would they. The motor is back in my Willys and is running strong (so far).