Knock is an interesting term you used for valve train noise. Most people here a "knock" sound from the block area, and a "rattle" sound from the valve training. I'm not sure what to make of a knock sound from the valve train.

What were all your compression pressures - dry & wet?

When you did the compression pressures, was the engine warmed up or cold? What the throttle body butterfly wide open or closed?

 

del

 

So you only checked the 3 cylinders on the firewall side?

And wet, all 3 were at 200 psi?

Dry, 1 & 5 were at 200 psi, but 3 was at 130 psi?

Was this with a warm or cold engine? Was this with the throttle plate wide open or fully closed?

Without knowing the answers to the 2 questions just above, I would say you have severe ring blow-by on #3 cylinder. But if you answer all the questions, I might have a differing opinion.

 

del

 

The frequency does sound like valve train, and there is a definite loud ticking noise (I would not classify it as a knock, but sound on a video is often not heard the same as in real life). The frequency is that of a valve train (half of engine RPM).

Do you have a misfire condition? What year 3.0L V6 are we talking about? Is it a 1MZ-FE engine?

That 130 psi is a problem, given 2 others are at 200 psi. Would be good to know whay cylinders 2, 4 & 6 are doing. If one of the valves in cylinder 3 was bad (burned, for example), I would think you would see a valve lash measurement problem (too tight). Did you check both valve on the intake cam, and both valve on the exhaust cam, in cylinder #3 (4 vavles total)? What were the valve lash measurements (clearances) of all 4 valves?

 

If you do another dry/wet test, prop the throttle plate fully open.

Also, get a Mityvac (Autozone's free loaner program, with refundable deposit), and measure the vacuum readings with the engine running. Do you notice regular drops in the range of about 4 in/Hg? That may be valve problems.

You may then want to do a leak down test. But from the data, looks like cyl #3 has bad rings.

 

del

 

Why would the ground electrode bend? You may have more damage in the cylinder.

 

So #3 cylinder has a significantly lower compression pressure than the rest when dry tested (but all are equal when wet tested) (which is a strong indication of piston ring damage), and that same cylinder had a bent spark plug ground electrode - pushed into the center electrode? And you have a loud ticking sound which seems to be of a frequency consistent with valve train.

Are you absolutely sure your wet (tablespoon of oil) compression pressure on #3 cylinder was at or above 200 psi? This just doesn't seem to all fit.

 

Are you absolutely sure your wet (tablespoon of oil) compression pressure on #3 cylinder was at or above 200 psi?

What about this question?

 

Valve clearances: 1 3 5th cyl
Exhaust:
13 (0.013) 13------- 13 13----------- 14 13 specs 10-14
Intake:
9 9 --------------------8 8 --------------10 9 specs 6-10

 

d

 

I had the same noise. (see link)
http://www.toyotanation.com/forum/1...neration-1992-1996-1997-2001/405249-hammering-tapping-grinding-noise-motor.html

It ended up being the timing belt cover, it was rubbing the pulley.
I replaced a very weak timing belt tensioner so that many of been a contributor too. If you can push in the tensioner with you finger, it needs to be replaced.

The noise drive me crazy. I even replaced a valve shim that was out of spec. with no change in noise.
With a stethoscope the noise was loudest at the water pump housing but after replacing it, the noise was still there.

Problbly not your problem but at least check both. Noises under the hood are very hard to find as the noise can transfer to a different area for some reason. Start looking in places that you may not expect.

 

.

 

I'll know tomorrow, I'll bring it to machine shop to listen.

You should tell them about the spark plug issue you had in the cylinder that has low dry compression too. I think there is a relationship with this piece of evidence.