Ok, here's the deal......view video and send in your diagnosis. A few points to note......Motor has good push rods, bearings, rockerarms and all other mechanical parts except what's causing this noise.

*Final Note: Noise goes away when we remove the #6 spark plug wire........

H-E-L-P

http://www.youtube.com/watch?v=cTvA1...ature=youtu.be



Here it is running good without #6 plug wire.....

http://www.youtube.com/watch?v=6StcU...ature=youtu.be

Compression test? Does it idle smooth? It almost sound like it is popping back thru the throttle body.

Is this a quiz, or do you really need help?

Nope, not a quiz.....Need help

SOUNDS LIKE NO. 6 WIRE IS ARCING SOME WHERE!!! LOOK FOR ARCING FROM COIL TOWER TO POST ON CAP.....kEN

do a compression test... could be a bad valve

Probably not much of any help here, but interested. Agree on the bad plug wire but sounds loud for an arc. very hollow sheet metal like and rythmic not steady. (is it just following the slight lope of the idle?) Rocker hitting valve cover?

How would a valve sound like that? would think more back fire sound if it was bad. If it was sticking and smacking the rocker arm or something it wouldn't stop just because you pulled the plug wire.

Don't shoot me here, but how about a wrist pin?

Not that you'd run it like that under load, but when it started making the noise[GOOGLEVIDEO][/GOOGLEVIDEO] was there any lack of power or anything?

Just throwing some ideas out.

Exhaust manifold gasket leaking at the #6 cylinder would be my guess.

What were you doing when it started making the noise ?

1) cyl 6 could be miss firing and causing the exhaust tio flap to bang away,,make sure theirs rubber on the flap or stichk your hand in the exhause when its running when the engineis stll cold(first starting the engine)

2) i have seen a misfire cause what they call a spark knock,,thats when the #6 cylinder is not firing on time and the cylinder prefires and causes a knocking noise...try changing the spark plug and start it,,if its still their try swapping the plug wire with the other engine..

3) broken valve spring and the valve is hitting the piston,,inspect #6 plug for color,,listen the that side of the exhaust,will sound different than the others..could be exhaust valve spring or even a bent push rod..

4) good luck!