OK i'm at my wits end on this one.

I have a 1995 chevrolet G20 van. It's equiped with a 4.3L TBI V-6. I
have a knock in the engine that shows up after its warmed up. If i were
to describe it, it sounds just like a lifter. I have replaced the
lifters ( very $pricey$ i might add, its a roller lifter engine ) with
no luck. This engine is equiped with the counter balancer by the way.
After doing that, i removed the inspection plate from the transmission,
unbolted the torque converter and slid it back out of the way. I fired
the engine up and the noise was still there. Next i removed the
serpentine belt and fired the engine up and the noise remanined.
Fustrated i searched the internet and i came across a GM Technical
Service Bulletin that said the exaust valve seals might be starving the
guides for oil causing the valves to bind. I went and purchased the
updated seals from GM, installed them, and noted no change.

The source of the knock seems like it is coming from the center of the
engine. I placed my stethoscope on the timing chain cover and i can
hear it. I have heard tales that the noise may be caused by slack
between the counter balancer and camshaft gears and supposedly GM knows
about this.

Its not a deep knock like a rod or a main and like i said earlier it
shows up after the engine is warmed up. The engine runs great, very
smooth, has good oil pressure, produces good power throughout the RPM
range and it only has 60,000 miles on it. The engine has been treated
to regular oil changes.

Thanks in advance!

PMB