trouble shooting before top-end instal

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97' Altima, auto, 230k!

I didn't really know how to title this one. Anyhow, One day my car started to run really rough and making a puff puff puff noise. No power at all, except every once in awhile it would be okay for 30sec or so. Changed the plug wires, no good. When I was changing the spark plugs, #3 was dripping wet with coolant. I assumed it was a head gasket problem. Drained the oil, no coolant in the oil, that I could tell. Pulled the head anyway.

When I finally get done pulling the motor apart to get the HG out, the HG looks fine. No blow outs, rips, or anything else out of the ordinary. I had the head dye tested and checked for warping. The head was perfect.

What is up? Can the HG be bad without any observable defects? Am I missing anything? I just don't want to put it all back together and it have the same problem. Thanks.