OK, here is an update.

 

I used a big screwdriver to my ear and checked the tensioner. It's not there. I also increased the tensioner pressure a bit by prying the tension wheel with a big screwdriver while reving the engine and saw no difference.

 

I then tried pulling the passenger side front cyl plug wire. (engine off, I've do that before). The noise went away. I plugged it back in and the noise came back. I switched to remove the plug wire from the next cyl. Noise is still there.

 

I took all the plugs out. The suspect cyl plug didn't seem totally tight an the gasket ring was left stuck in the cyl head after removing the plug. Around the seat on the rubber plug cover there was what looked like some fine white ash. Could be a micro leak around the plug seal? Could also be aluminum oxide powder from some casting corrosion?

 

I checked the compression and it was ~180 on the passenger side cylinders. I could not do the driver side since my test tool won't fit in without removing the washer tank and battery.

 

I made a tool out of an 8 inch nail to pull out the seized plug seal ring.

 

I re-gapped all the plugs, put anti-seize on the threads and re-installed them.

 

After starting up it seems there is no more knock. So what was it? Could it have just been a bad spark plug seal? If it was piston slap it sure sounded exactly like the numerous loose rod bearings I've had experience with. Not that I'm complaining about it not being rod knock.

 

I'll now invest is a timing belt and new pulleys.

 

Thanks for the advise. I'll report back if it turns out the problems are not solved.

Edited February 6, 201313 yr by dburton97128
Sp

I have no possible explanation. It fits the MO of rod knock, but rod knock doesn't go away just by changing a spark plug. Keep an ear on it. Check for sparklies in the oil next time you change it. I would hold off on timing parts for now.

have seen rarly all the carbon fall off the piston and colect on the bottom side and build up enuff to hit the head mabee thiss mabee a motovac or valve cleaner.

Well I did something dumb.  When I put the knocking cylinder spark plug back it I somehow bent the tip and closed the gap.  Since it was not firing the knock sound was gone.  I got to noticiting it ran a bit rough and so tracked down the non-functional plug.  I had not driven it, just run it momentarily with the covers off.

 

After fixing the plug I can still hear the knock if I try hard to make it happen.  It's still way less than it was before so maybe it is piston slap.

 

I put in a new Ca belt ($30) and re-lubed the old pully bearings.  We'll see how long it goes, buts it's been more than a year already and the knock hasn't gotten worse, in fact it's gotten better.

Edited February 8, 201313 yr by dburton97128