<VV> update: mystery engine knock in recently rebuilt 66 Monza 110 PG

[Jedd Hebrink]

Thanks to all of you that have offered suggestions and ideas as to what
might be causing the knock in my recently rebuilt 110 engine.  For those of
you that don't remember, after rebuilding the engine due to a broken rod cap
last summer, the engine developed a disturbing knock after about an hour or
so of driving at about 60 mph.  In my initial rebuild, I had the crank
ground and replaced all cylinders, pistons, rings, connecting rods and, of
course, gaskets and seals.  I also replaced the fuel pump.
 
To recap a few of the suggested causes that I have been able to rule out:
flex plate bolts are tightened to specified torque (30 ft pounds).
compression was good in all six cylinders, so I am thinking no dropped valve
seat.
valves were all adjusted (and readjusted) properly, rockers and push rods
all checked out okay; I don't believe this is a valve train issue.
spark plugs were all okay, no sign of pistons colliding with plugs.
I turned the engine by hand with the plugs out.  Could not detect any sounds
in any cylinder that would indicate a problem.
I pulled the heads off, and no sign of a dropped valve seat, nor any debris,
miscellaneous parts or broken bits in cylinders.  Also, no signs of broken
pistons or rings.
I took the fan assembly off and viewed the rods and caps.  No sign of
anything striking any other part inside the crankcase.  
 
At this point, I plan to pull the remaining drive train out and split the
case to inspect the bearings.  I will Plastigage them if there is no obvious
damage to the bearings.  I will check the crankshaft for any obvious signs
of a fracture.
 
Does anyone have any other suggestions?  Anything I may have overlooked?
While I was worried right from the start that I may have a rod or main
bearing issue, I am a little surprised to get this far into the engine
without any visible indications of where the knock is coming from.
 
I sure appreciate all your valuable advice and your patience as I continue
to work through this.
 
Jedd Hebrink
66 Monza 110 PG
Wimberley, Texas
 
 
 

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