Need help identifying noise. Rod knock ?

[Road Trip]

Genius! ^^

Controlling the spark energy Schurkey's way vs just letting
it fly the old school way is 100% preferable, especially since we are no longer
working with a purely mechanical points/condensor setup. (ie: Think 5.0V
ECM circuits woven throughout the engine bay succumbing to collateral damage
due to eating/sinking stray high KV sparks.)

Also avoiding stressing the isulation of everything in the spark delivery
system is intelligent.

I stand corrected. But this is also how I learn -- will be using this approach
from now on. Old-school caveman appreciates the tip!

 

[Scooterwrench]

Mostly good advice, however don't "pull" the plug wires. This leads to an open-circuit for the secondary voltage, which then goes sky-high and is very hard on the coil, coil wire, distributor cap, rotor, and plug wire.

Instead, kill the spark by sliding small nails BETWEEN the plug wire and the plug wire boot at the distributor cap. Then use a 12V test light (incandescent bulb) or a jumper wire to ground the spark to each cylinder. I blunt the sharp point of the nails, and use a bit of Silicone dielectric grease on each one. DO NOT pierce the insulation of the plug wire/boot. The goal is to slide the nail between the wire insulation and the boot until you feel contact with the metal end of the plug wire.

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Grounding the spark isn't hard on the insulation of the ignition system, the way that an open-circuit is. Remove the nails when you're done, or they short on the air cleaner.

That's a cool trick,I like it!
Another reason to not pull wires is the possibility that you may need to go change your shorts. If you ever get nailed by an HEI you will never forget it.

 

[Schurkey]

Another reason to not pull wires is the possibility that you may need to go change your shorts. If you ever get nailed by an HEI you will never forget it.

...especially if the spark grounds through your pants-zipper on the fender. That'll wound Mister Happy.

 

[RamonRdzS]

I've also troubleshot down low noises despite good oil pressure. In both
cases that I can recollect, the root cause of the knock was a bent/twisted
connecting rod.

In the first case a recently purchase truck had a sound
similar to the OP's video. But at the same time oil pressure was within limits?

After removal & subsequent teardown, it looked like the PO had suffered
a hydraulic lock (due to a head gasket coolant leak) into 1 cylinder.
The head gasket had been replaced, but the reciprocating assembly was
left as-is? And while the engine more or less ran on all 8 cylinders after
the head gasket job, but this one cylinder was noisy similar to the OP's engine?


In the 2nd case, the rod was twisted, and because of new stresses induced
because the wrist pin was working cocked, the piston slap had become
authoritative, and was present cold or hot?

Weird things can be hiding inside an engine, especially when it comes from
the used car manufacturing plant. The previous owner's 'good enuf' is now
your new baby's WTF?

Q: Was this engine ever quiet for you? If so, did it come on slowly over time
or did it suddenly appear? Or did you buy it for the right price with this
noise evident? This might help us narrow down the possibilities...

When I bought it it had no wierd noises, after about two months it would start ticking when cold but would go away after a few seconds, now it doesn't go away.
A mechanic told me it was a spun bearing and that he would have to take the engine out. No diagnostic only heard the engine and told me "You got low oil pressure right".

 

[Road Trip]

If you ever get nailed by an HEI you will never forget it.

That is a 100% correct statement. Exactly ONE time I inadvertantly
located a bad spot in the insulation on a HEI-driven spark plug
wire with one hand, and it felt like a mule kicked me in the arm!

Eff me! I felt a little dazed & confused afterwards. Guess I was
most fortunate that I was working one handed and didn't take it
across the chest. (Only takes ~50 milliamps to stop the heart.)

I have hard-won respect for HEI systems. If anything catches my eye,
engine gets shut off, and *then* I look. Like you said, I'll never forget
that HEI mule kick...

 

[Road Trip]

Did the test. Drive, break and accelerate and it's still knocking. Parked and accelerate to 1500rpm still ticks. Forgot to mention, tick is faster with rpms.
Oil pressure on start:

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OK, good to know that in the not too distant past the engine ran quietly & this came on
gradually over time. (As opposed to a barn find start up where the noise was there
from your beginning with it.)

****

If it was me, I would show him this oil reading & ask him what's his definition of low oil pressure?
Not being confrontational, just trying to reconcile his diagnosis vis-a-vis the gauge reading?
Has he proved/disproved the accuracy of your oil pressure gauge? Or just pulling this
broad-brush diagnosis out of his back pocket based on previous experience?

Others feel free to jump in & correct me, but I've found that changing the engine oil viscosity
for the purposes of troubleshooting this kind of scenario will help me decide if the problem is an
out of tolerance rod bearing vs piston slap/knock. For example, if you are running 5W-30, then
changing to a 10W-30 or 10W-40 and having the noise either change or remain constant would
tell me which way to go. And of course, if you are running a 10W-30 oil, I'd switch to a 20W-50
oil & repeat the listening session. (After all, it does have 190K miles on it.)

If the sound diminishes or disappears, then we know that you are towards the end of the service
life of the rod bearing. In this case, by adopting the new (work around) oil viscosity, this will buy
you some breathing room in order to come up with a solution that works for you.

And if the noise remains, then now I'm looking at the other end of the connecting rod. Piston slap?
Who knows, some people have driven a long time with piston slap -- more of a audible nuisance than
outright showstopper?

****

Of course don't take the above as any kind of guarantee that it won't rapidly worsen if left as-is
and possibly strand you. Until I had a better understanding of what's causing the noise,
I would abstain from towing a horse trailer, boat, toy hauler, etc. As a matter of fact, I would drive it
gently & monitor the oil pressure diligently.

Again, there's several folks with a lot of experience urging you to dig a little deeper. Watching
your video, you might be able to start with the #5 or #7 cylinder and locate the noisy assy
on the first couple of tries. Drop the inspection cover & verify the tightness of the bolts
between the flexplate & the torque converter? Or maybe change the oil to a thicker viscosity & listen.
(NOTE: Change it yourself, a lot of Jiffy Lube type joints will write down your request & then put whatever
is in the 55-gallon bulk oil drum anyway. :-(

Anyway, do some controlled testing and report back. And thanks for getting back on whether the
engine ever ran sans noise or not.

My 2¢ worth!

 

[RamonRdzS]

Ok so before I go out testing, I should mention, I was running 5w30 and the mechanic told me to run thicker oil 10w40. Noise actually got louder, so I thought it might be a lifter or something but if it were a lifter it wouldn't be knocking and the noise seems to come from below.
Also let's say it is a spun bearing or a bent rod, is it worth getting it rebuilt ? The quote on rebuilding it where I live is arround $400 bucks of labor plus parts.

 

[Scooterwrench]

$400 for labor for a complete rebuild is scary cheap,I'd be wary! Sounds like a get you in the door price.
Bent rods are rare,bearings wore out are not. If heavier oil made it louder I would suspect a collapsed lifter.

 

[Schurkey]

The core short-block I bought from a Treasure Yard to rebuild for my '88 K1500 came out of the donor vehicle because it had a "rod knock". They were convinced the engine was "done".

As it's hanging there on the engine hoist, they figure out that the flexplate has a full-circle crack just outside the bolt circle where it attaches to the crank. The outer part would wiggle back and forth on this irregular circle--not so round that the outer part could actually spin, but the crack went all the way around, the inner part was entirely detached from the outer part.

The salvage yard sold the heads off of it (Vortec 5.7L) and some months later, I bought the short-block. The rod and cam bearings had wear, I re-used the mains.

Moral of the story: One-piece-rear-main-seal flexplates are infamous for cracking which sounds like a bearing knock.

 

[Hipster]

One-piece-rear-main-seal flexplates are infamous for cracking which sounds like a bearing knock.

.... and pretty much sound like the video posted