CHIRPING LT1

[z28ed]

My 95 Z28 makes a loud tap-chirp sound at idle that is in sync with timing light flashes. As the engine speeds up,the sound gradually transforms into just tapping.With a stethoscope, the sound comes from deep within on the passenger side.I have not yet found any exhaust leak(but it still could be),and the noise was there before my recent valve job too. If a lifter is failing/or has collapsed internally,could that be what I am hearing?I now have Isky valvesprings,and the chirpie noise started back up after 100 miles on redone heads.I have heard of a similar sound in Impalas that is supposed to be a sticking valve.Is that a possibility?My chirping is louder than my Flowmaster exhaust,so this is no little thing!Also,I failed smog HC by 5 parts per million even though all other emissions were below the averages. Could the charcoal cannister be leaking into the atmosphere?I have new heads,plugs,and wires.Will alcohol mixed with gasoline cut the HC numbers?And,due to the noise,my tank is near full of six month old fuel,could old fuel raise HC counts ?
This is my third try at submitting a post, am I unlucky in everything?

[Joe 1320]

Please don't post in all caps... it's in the rules.

Could be a bearing. Just for kicks, I would disconnect the spark plug wire, one at a time and see there is any difference whether a cylinder is involved a combustion event or not. In short order, if the noise goes away on a cylinder when the spark is disconnected, that points an internal problem with a wrist pin, piston, rod or bearing. There is also the possibility that an external accessory like the tensioner is transmitting sound to the block, but a stethescope would have pinpointed that. If the noise doesn't go away, main bearings or camshaft bearings/lobes may be damaged. I've never heard a lifter make a chirping sound. There could also be the possibility of a loose spark plug or headgasket leaking to atmosphere.

Let me get this straight...... the noise was there prior to a top end rebuild. It went away after the rebuild but after 100 miles it
returned. That could be cam/valvetrain related..... maybe a cam lobe going flat, failure of new parts (don't be suprised there), or a host of other possibilities.

Tough call without having hands on.......