96 Saturn engine knocking

Hello:

I have a 1996 SW2 that had low compression and high oil consumption. Last
summer, I pulled the engine, tore it down and sent the block, crank, head,
etc off to a machine shop. It came back with a rebuild kit, bored out block,
rebuilt head, turned crank, etc. It took a few nights to put it back
together, but it when I put it back in, it started on the first try. It had
good compression and the oil consumption stopped. As a side note, I replaced
every sensor, gasket, etc. that I could find on the engine before
reinstalling it.

A few weeks later, I noticed the head gasket leaking antifreeze most of the
way around. I took the head off again and went to the dealer and bought head
gasket and new head bolts. I noticed the dealer gasket was thicker than the
rebuild kit one and seemed to have an orange "rubber band" running through
it. I reinstalled the head and other stuff and the leaks were fixed. It was
running as good as new.

Now, its a year later and my wife mentioned a "knocking" noise. I took it
for a drive the other day and sure enough, I thought the engine was falling
apart. It has good performance, good milage, isn't using any oil, no
antifreeze missing from the coolant tank and no trouble codes set. But, when
cruising, it knocks so loud I think it's falling apart. Under load, the
noise completely disappears. Under idle it's fine, but rev the engine to
about 1200 rpm and it shows up.

Should I be worried? Any suggestions on where to start? Is it possible the
head gasket is leaking again?

A friend suggested a problem with the lifters. Another said the pistons were
loose. How would I know? By the way, I bought a new torque wrench for this
project and carefully observed the specs and procedures in two different
manuals.

Thanks in advance.

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