Well an engine knock can be a number of things..
Attach an oil pressure gauge to the motor and insure you have
oil pressure. Pull the valve cover and make sure oil is reaching
the valve train assemblies..
Even if the motor was rebuilt, if it sat for some time
and the oil pump was never primed or lost prime. You may
have damaged either or both the main or connecting rod
bearings.. Result. dammaged bearings / crankshaft
Pistons are really barrel shaped. If the piston to wall
clearance was not checked, and is too loose, you may be
getting what is known as piston slap as the skirt of the
piston bangs against the cylinder wall due to loose
tolerances. Result scorred cylinder walls
If the head or head mate surface of the motor block was
machined to eliminate any warping. And the piston depth
in the cylinder was not checked. And a thicker head gasket
used to compensate for the reduced piston to head clearance
was not used or no machineing and a wrong thinner head gasket
used. You may have a piston to head clearance problem in which
the piston is hitting the cylinder head..
If someone goofed and dropped an extra lets say rod connecting
rod bolt, nut in the motor.. or any foreign object that fell in
during the rebuild..Or down the intake port same difference ..
If they changed or reground the camshaft, it may be wrong
and the valves may be hitting the pistons ..
If the knock is not bad use a stethoscope to determine where
in the motor the noise is coming from. If a bore scope is available
pull the spark plugs and look in the cylinders. Drain the oil and
look up in the crank case.. Filter the drain oil thru a paint
funnel filter (available from any automotive paint store) look
for any metal chips. Cut the oil filter apart and look for metal.
If found the composition of the metal type will indicate the
problem area.. Bearing material, aluminum.. pistons.. ect
Next would be pull the oil pan to see whats happening.
Other than that its pull the motor out of the vehicle and tear it
down to find the problem...
Bob B
>From: "Dean L. Kellogg, Jr" <kelloggd@uthscsa.edu>
>To: <mil-veh@mil-veh.org> (Military Vehicles Mailing List)
>Subject: [MV] Hercules JXD engine "knock"
>Date: Tue, 14 Nov 2000 09:28:23 -0600
>
>Dear learned listees,
>
>I am evalluating a vehicle with a Hercules JXD engine. The engine was
>"rebuilt" several years ago, but now has a "knock". Please help me out of
>my ignorance.
>
>1) What are the possible sources of the "knock"?
>
>2) How is the source of the "knock" best diagnosed?
>
>thanks
>
>*****************************************************************************
>Dean L. Kellogg, Jr., MD, PhD
>Department of Medicine
>The University of Texas Health Science Center at San Antonio
>7703 Floyd Curl Drive
>San Antonio, Texas 78229-3900
>(210) 617-5311 FAX (210) 617-5312 e-mail:kelloggd@uthscsa.edu
>******************************************************************************
>V
>
>
>
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