Name that sound!

alternator, power steering, a/c belt all disconnected. So narrowed those and water pump bearings out.

swapped alternator. Still happens. Checked spark plug wires. All connected.

Started about three minutes into a drive. recently added timing control to existing MSD atomic system. Ran better than stock distributor.


things I have tried...

Added 6 ounces of Seafoam to oil. Oil looks pretty clean. Running Rotella T5 15/40 with aN extra zinc additive.

engine is 3 years old. 3500+ miles. 455. Rebuilt heads and new bearings and resurfaced rods and all surfaces. All to Olds Specs. Comp cams pushrods and stock lifters. Roller rockers. RV Stock Cam. Ran great till today.

thoughts? Should I crack open the driver side valve cover and look? What is next in trouble shooting?

 

Cracked pedestal mount for rockers?

 

seems fine. They are ARP. Torqued to spec. Each rocker was zero lash when installed. Looking at the wear on the push rods against guide plates seems to indicate they are all moving.

 

Just disconnected distributor and cracked engine watching the rockers. They all move up and down.

 

I wonder.... could it be the mechanical fuel pump? It was new three years ago, and was only used for the initial break in of the engine before installing the MSD Atomic. It has not been connected to a fuel source OR to the engine since. It is just there, idling along with the engine. When a mechanical pump goes bad can it make a sound like that?

 

You say zero lash, if your not running a solid lifter cam hydraulic cams require at least a 1/4 turn in from 0 lash.

 

Definitely coming from top of engine?
Does the frequency increase with RPM?
Does it now happen at start up? Just at temperature?

Could that be a loose flexplate bolt?

-peter

 

I had a similar noise (without what I hear as a squawk) with a brand new mechanical fuel pump on a 460 Ford.
Sounded like valve train noise and with stethoscope it was definitely louder on right bank. Ford pump is mounted on left side of timing cover.
After pulling valve covers and checking with no problems found I started thinking about the last few new parts I had installed that could make noise. Pulled the pump and operating by hand there was a noticeable rough click. Pumps are cheap so ordered another different brand and noise was gone.

Worth checking.

Flexplate not cracked and bolts are tight?

 

I kinda think I remembered having this sound...Pulled the flexplate, inspected for cracks and then remounted and really tightened the bolts down and problem was gone.

Pump’s a good answer too...but I would expect that to be faster...? Maybe?

 

Not the mechanical fuel pump

I took it off.

not the spark plugs. Bought new ones. R46sZ. Gapped to 40.

started up engine from five hours sitting Cold and still makes the sound.

 

The more I run it the more it sounds like a small missfire or backfire in the exhaust manifold.

would a blown out muffler or something cause this? The exhause pipe out back is new but the dual mufflers after the exhaust manifolds are unknown age.

 

another video. Sounds more like a miss? Or an valve not closing all the time?

 

Could you rev the engine a little?
-peter

 

Take a wooden broomstick - place one end on the opening of your ear, place the other end on various areas of the engine and associated parts. Identify the area with the loudest & most marked sound.

 

sure.

 

Stick a piece of 1/8" vacuum hose (3-4' long) in ear other end probe around engine. Works great-really...

 

I could not hear that noise in the first video. That is an odd one, maybe an exhaust manifold leak.

 

That is bazaar...it definitely changes with rpm but not perfectly....
Maybe it IS exhaust related. Have you felt with you hands around the manifold to see if you can feel a leak?

Does the noise change when you put it in gear?
(a loose torque converter bolt usually quiets down)

Also...did you by chance put one of those plugs in your crossover?

 

I have mondello stainless crossover blockoffs glued down with copper high temp RTV with FelPro gaskets over the top.

I was looking at my dual mufflers. One has black burns along the seems and is slightly “fatter” than the one next to it. If a squirrel or a rat built a next in my exhaust or muffler over the winter would that have caused the muffler to blow and does a blown muffler cause funny sounds in the exhaust manifold?

i am replacing the exhaust manifold gaskets tomorrow including the Donuts.

meanwhile I added some Marvel Mystery Oil to crankcase and sprayed some Penetrating Oil all over the valve springs and lifter pushrods to try soak.

 

I hope its just some critter debris in your exhaust. If you could temporally seal off any suspected exhaust leaks, might help. I kinda doubt it.

I'm not a fan of those flimsy thin block off plates, now that you mentioned them...part# HR 351 by chance? They burn through easily and could cause small pieces to break off and just bang around in the cross over area and not pass the exhaust valves.Temps are very hot in that area.

I'm just spit balling, you've got some strange sounds in there and I hope you find the problem.

 

Seems to me it that the rhythm of the knock is at a longer duration than what every eighth cylinder firing would be. Thus it shouldn't be piston rod related I would think. This is a strange one..... Tedd

 

Someone suggested to disconnect each spark plug wire one at a time to see if I can narrow down if the sound is indeed a valve not closing and what I am hearing is maybe a misfire into exhaust manifold.

Is that safe? How do I accomplish that? Without getting zapped by the HEI

 

checked that this morning. All three bolts are tight.

 

Just use pliers with rubber coated handles if your wires and boots look sketchy. If for some reason you do get nailed by HEI you won't die but I'll guarantee you will drop what ever you have in your hand at just about the speed of light.

While you are playing with your wires you might try grounding a wire so you can hear the electricity snap and see if it is at the same rhythm as the knock you are trying to find. To me it seems to be slower than what the firing of a plug....... Just a thought may be nothing.... Tedd

 

I

bought this guy to ground each wire one at a time.


If that eliminates the noise what will I have proven?

 

IMO, the 'noise' has a pulse of approximately once/second - 60/minute when at idle assuming idle is ~1,000 RPM. It appears from the sound this is positively correlated to engine RPM as the noise interval increases as the engine RPM increases. I wouldn't think it is directly correlated to spark (pulse) since one cylinder on a four stroke should be firing at the rate of ~500/minute @ 1000RPM. That's far faster than the 60/minute I'm hearing.

One cylinder assembly (rod/piston) moves up & down 1,000 times @ 1,000 RPM (one/crankshaft rotation), but fires once per every two rotations. [1000/2=500]. The total firings for an 8 cylinder 4 stroke engine @ 1,000 RPM should be ~500 firings/minute/cylinder x 8 cylinders = 4,000 pulses/minute.

The noise (clack) sounds mechanical and IMO does not appear related to the 'pulse' of spark plug firing.

I would definitely without hesitation take a wooden broomstick to that engine and probe for the clack.

 

Sounds like a cracked flex plate to me.

 

^^^Has my vote^^^

 

got under there yesterday and rotated it all way around and checked. Looks brand new. It was a brand new one three years ago. Heavy duty version new from Summit.

 

Again, a dowel rod or broomstick works absolute wonders in this type of diagnosis. You should be listening for this noise w/ the engine running and again, w/ a broomstick or wooden dowel rod firmly planted onto the opening of your ear. Turning a flexplate does not necessarily equate to no crack or not being warped. Ensure the bolts are solidly holding the flexplate. There's (obviously) a tremendous amount of pressure exerted on the flexplate and it is designed to do exactly that - flex to compensate for imperfect engine alignment. Not certain what flexplate you have, but hopefully the rebuild was done correctly (e.g. all dowel pins inserted correctly, bolts tightened properly). It does not sound pulse related to engine firing, it sounds mechanical - did I mention the broomstick thing?

While perhaps unlikely, but certainly possible, there's an off chance you have something 'stuck', or 'wedged' up into the housing? Do you have a cover which is normally covering the flexplate? A wire jammed up in there, a stick or something?

 

went to big city to buy a broom. Cant find any near me.

 

It doesn't necessarily 'have' to be a broomstick. A piece of wood (preferably) fashioned long enough (square, rectangular whatever) will transfer the emanating noise directly through any piece of wood held onto any area of the engine (or assemblies) onto your ear. Nothing laying about?

 

You'll find many of these stick tricks I suppose on YouTube (they work). Listen to this chap trying to diagnose a noise. Pay particular attention to the noise emanated by the firing of a fuel injector through a piece of wood. That should provide you w/ some reference in exactly how a piece of wood mimics a stethoscope. While a stethoscope operates via a hollow tube, you want that noise to travel (emanate) from the source to your ear. A stethoscope employs a vibrating diaphragm to capture the noise then emanate that noise via the hollow tube. Greg (above) suggested basically the same operation w/ a piece of vacuum hose.

 

https://www.freeasestudyguides.com/e...cuum-test.html

sorry I tried to upload the readings no go
but you should be able to click on the link '
may help to narrow down internal or external issue/noise

 

probed whole engine. Sound is coming from front driver area of the block. I dont hear anything odd in the valve cover.

i took a video of the exhaust with paper flap. Not sure but that looks like paper is getting sucked in?

 

Here is exhaust video full speed.

 

I was just thinking, is there a heat riser on the exhaust manifold?

 

No. It does not appear the paper is getting sucked in.

I think you should fine-tune the probing. Probe the head & probe the block in numerous locations of each. You should be able to discern the knock between the head and the block. Probe the LH-exhaust manifold at each exhaust port. Probe the PS pump (which I assume is located on the same LH-side as the 350 sbo). You may have thrown a bearing in the PS pump (or whatever), but probe the PS pump itself. Additionally, probe the alternator (which I also assume is on the LH-side; unless it does not have AC which then I suspect it may be located on the RH-side - I'm not reviewing a 455 bbo either w/ or w/o AC). Bottom line, I think you can narrow this down further w/ better probing. Finally, you can record each probe you make with your iPhone (phone) turned on. Hold the piece of wood 'on' the phone w/ video capture. Then we can all hear the sound. You're inching your way closer.

 

nope. Never had one.

is there such a thing as an intermittent stuck valve or any reason an occasional misfire would happen?

what does a burnt valve do?

 

Could be. You'd need more 'tissue' rather than paper to demonstrate if it's really getting sucked in. Check out the (below) video. Also, perform a compression test you should see a noticeable difference in compression (or, a leak-down test). That should help determine if you're heading in the right direction regarding a malfunctioning exhaust valve. Although, I'd think the sound would be more rapid than what it appears to sound like. At any rate, perform a simple compression test and possibly fine-tune your probing.