Got a carbed 2.8 V-6 in an '85 S-10 Blazer. (not original engine -- omit long sad story ) It's got a noise and I would like to narrow the possibilites down before I decide what to do. (17 year old son flipped his Neon -- didn't even need a band-aid but car is totaled. Yes, he believes in seat belts now ) Noise is a tapping/knocking, seems to be in top left rear of engine. One guy says wrist pin, another says lifter, etc. It's worse under acceleration, but not always. What can I check to help narrow down the problem? I've got a stethoscope to help. I've been told to pull plug wires to see if it stops the noise to isolate which cylinder, but is there anything else I can do? Love to put a 3.4 in it, but can't find one, etc, etc, etc.