If I understand this correctly, this engine has a balancing shaft. If I was looking at it correctly, it looks like it runs across the top of the Block just under the Intake manifold.

It looks like this engine does not have a chain, it hase two gears?
http://www.hotrod.com/techfaq/113_07.../photo_05.html

Is this correct?
Just wondering if this Hard Knock issue might be coming from a loose Balancing shaft that is boucing around under the Intake.

 

The 4.3L has a balance shaft as you say, but there is definitely a timing chain on it.

 

https://blazerforum.com/forum/showth...298#post227298

Here's my Post from earlier.

I have yet to do a compression check. Just the other day it got quieter, So I drove it. It drove fine. Plenty of Power again. So it's an interemitent problem, I doubt it's the bottom end.

Am I correct with the valve cover Oil Fill neck, a 1/4 turn to loosen then pull up? I can't get this Neck off.

 

I just read your previous thread on the knocking problem. Let's keep things all in one thread when they are connected. I am combining these two threads.

 

Spark Plugs are even and clean.

Drained oil through a paint strainer and no metal filings.

I wanted to check the tightness of the Transmission Torque converter bolts but there is no inspection Plate on these cars. How do you do it? I see a 2" diameter tin plug on the bellhousing, is that it? Still can't get the Oil spout to come out of the Valve cover

 

Finally got the Passeger Valve cover off. After it was out of the car I got large WaterPump Pliers on the Oil Fill Neck and coaxed it off. After it was off I can see that the Rubber 'O' ring was all screwed up. Now it comes of and on as it should.

Bad news is that everything looks and rocks as it should as I hand crank the engine around. Now that it quieted down dramatically, I don't think I will see the problem if I start breaking the Top of the Engine down. I think I need to start driving it again until I get that hard knock then redo the compression check.
Very puzzling. I've been working on my own cars for 30+ years I own 3 cars with more than 300K miles on them and have done all the maintanence on them and this is a mystery to me.

 

the section of the harness across the valve covers and intake can be moved completely out of the way by taking fuse panel loose on driver side fender and uplugging the center large weatherpack connector from the backside of the box. (it will have a 5/16 screw holding it in) Then, just unplug each of the connectors along the way including the injection plug. Drape this section over the batterybox/coolant tank. The valve cover comes out very easily now with just three bolts. Good luck

 

If it were a problem in the bottom end, it should not have just gone away. Sounds like it could have been a stuck lifter...

 

ok i dont know if this has been suggested yet but check for a burnt plug wire or just try changing out all your plug wires it dosent sound like its mechanical at all to me it sounds like its not firing on a few cylinders (loss of power engine shaking etc.). CHeck for spark on all 6 clynders. I have had this problem b4 on a customer car and all it turned out to be was a burnt wire.

 

For those who've been watching this.
Here's the Findings.

Rear Passenger side Roller Lifter has a husge flat spot on the roller section. It screwed up the Lobe on the Cam , obviously.

Asking a few Mechanic friends I have, they said... This is extremely rare "just a fluke thing".

So I guess the lifter was hanging a bit and the Lobe comes around and Whacks the flat on the lifter causing that horrid deep Rod Knock sound but then when it quieted down it tapped like a semi sunk lifter which is because the length of teh Lifter is shorter with the Roller be worn. Again, with the top of the engine off, it looke like this was not a case of oil starvation... it's very clean under there.