Technical BBC Hammering & Squeaking

This is almost embarassing. My shop truck has a 454 that suddenly developed a hammering sound with an attending squeak. It is scary loud but not like a rod knock. It seems to be coming from the front of the engine. Drivers side may be slightly louder, but I'm old with poor hearing.
Here is what I have done so far:
Removed the alternator and AC belts to eliminate the water pump. No Change

Checked the timing with a light to see if chain might be loose. The timing is at 8 degrees no vacuum advance. Revving the engine a bit, it advances a few degrees. Letting it snap back to idle, the timing returns exactly to 8. No evidence of chain whip.

Listened with a tube to timing cover, fuel pump, intake manifold, valve covers, oil pan etc. Nothing sticks out as being the source.
Checked oil pan for dents. Nothing there.

Oil pressure is @ 30 psi.

I attempted to post a video, but it didn't work. any tips on doing that?

This has me stumped, I have never heard anything quite like this before. It just started out of nowhere. The truck doesn't get driven a lot, but it always starts and runs great.

 

Harmonic balancer loose?

 

Clutch/transmission area...flexplate cracked...something in the clutch/broken clutch finger...bolt backed out and rubbing...?

 

What year is the engine?
The ones with roller rockers were known to squeak if a push rod bent or the roller started to fail.

 

Hammering and squeaking sure sounds like a rod bearing. Oil pressure can still be good as the bearing is probably smeared in the oil passage.

 

Thanx guys,

I'll check all the things mentioned.
The noise does increase in frequency with rpm but not steady like you would normally hear from a rod. It does seem like it's coming from the front.

I haven't checked flex plate yet. But it does sound like that.
The engine is an '86 so no rollers.

Wouldn't the harmonic balancer show up somehow with the timing light test?

A video would be helpful, I'm working on that!

 

Does it have power steering? I recently had a GM PS pump pulley come loose....made some ominous noises till I found it.

 

It does have PS. Can't hear anything in that vicinity and the power steering works fine.
Will pull that belt off too and check

 

Squeak.......squeal is often a sign of a failed and/or spun main bearing. Squeak is dry bearing shell turning in block. pressure is good because debris from back of main bearing shell has plugged oil passage in block so no big oil loss. On a slightly less ominous note...... galled or scored valve stems will give a similar noise.......possibly caused by overheating

 

This isn't the greatest, but I can do a better one if that would help!

 

If a bearing spins in a rod, it can block off the oil hole. That rod won't get any lube, but the oil pressure will be okay. Do you have any vibration along with the noise? If it does it with all the belts off, I'd check the back end flywheel/flex plate like others have suggested. If that's all good the pan is the next thing that needs to come off.

 

It would be nice to hear it rev and come back down. A rod knock is normally worse off load; when it coasts back down from a rev up.

 

water pump?

 

Muffler bearing.. ..Couldn't resist. Does it alter in gear?

 

That sounds ugly....is the dust shield between the trans and the engine bashed in? I had an engine make weird noises like that, that purred like a kitten once I removed the shield.

 

Sounds like an intermittent double knock. Squeal sound like an old belt chirping.

 

I'll get back on it tomorrow. Lots to check out.

 

This is a good one to use a hose as a listening device to narrow down the source of the noise. One end of the hose to your ear, and the other end around various parts of the engine/accessories. I'd pull the belts off and start it and see if the noise is still there with no belts on it.

 

Engine stethoscope,,,,,,cost only a few dollars,,,,,,you can safely diagnose any noise in an engine .
They work !

Tommy

 

You can also pull plug wires one at a time while it's running/knocking to find out if your issue is associated with a particular cylinder.

 

A double knock usually indicates a piggy backed rod bearing allowing the piston to hit the head. (Not in Naval vernacular) 270ci has the right idea as far as locating or eliminating cylinders.

 

Flex plate broken

 

It sounds ugly. I did have a #1 main spin on a 454 and broke a crank or visa versa. It sounded just like that.

 

I had a fuel pump rod make all kinds of weird noises on a 454 . I pulled the fuel pump and the plug to find the rod binding up and it took pliers to pull the S.O.B out. I ran it over some 400 grit sandpaper, oiled it up and reassembled. Noise went away. Strange I know. I think being gummed up it wasn’t returning fast enough and the cam eccentric was banging up against it ??

 

I’ve seen belts causes noises like this
Damaged power steering pump
Bad balancers
Timing chains

the chain is usually more “ rattely” the a knock .

also torque converter/ flex plate bolts
Tranny inspection covers can sound like the world is coming to an end is they get bent a bit.

Other then that it could be internal , usually rod knock or main knock is rpm driven.

balancers that sepperate can make noise even after shut down is the rubber is really torn apart.

I had one years ago that sound like a super charger winding down when I shut the engine off , told people I had the mad max blower on my car and “forgot to disconnect it “ on shut down