The Stovebolt Site Forums The Shop Area Engine Shop Name that noise!

Hey everybody,

Got my first classic not too long ago, a '61 C10. Engine started making this noise recently and I don't have anybody to ask about it. I'm new to all things mechanical but I'm trying to learn. It's a 235 straight six.

Here's a quick video I made to capture the sound:



Kind of reminds me of bike spokes slapping against a playing card. Any ideas? I replaced the head gasket but the noise is still there. It is possible I did not do that correctly, but I believe I did. Any help is greatly appreciated.

Thank you!

I can't help you with this noise but I guarantee that once it is solved (if it needs solving) and quieted, there will be another slightly quieter one to wonder about.

Run it with the valve cover removed. I'll bet you will find where its coming from.

First thought is an exhaust leak. Does it get louder when you hit the throttle?

*side note: Video doesn't always capture sound the best. I just took video of my engine break in and it has no exhaust past the manifold. The video didn't capture the loudness of the lack of exhaust!

Exhaust manifold gasket leak? If so, try a Remflex gasket, rather than an original style gasket. It is more expensive, around $35, but will seal gaps from corrosion or warping of the manifold up to 1/8 inch.

Kent

Remflex much cheaper on Amazon, I have needed 3--Bill

Yep, got some sticky valves there IMHO

If it's a sticky valve, should I adjust or replace?

Well my guess is something in the rotating assembly. The noise sounds too rapid to be a single valve or an exhaust leak. My bet is on a piston, rod and/or wrist pin issue. IMHO.

SimS

Main bearing knock

I'm with Jerry. Pretty heavy knock. A rod would be a bit lighter and more rapid.
Looks like a lower end rebuild is in your engine's future.

Wow, I'm floored you guys can get a reciprocating noise out of that. Not doubting you a bit but I can hear intake air and exhaust exchanging there, so can Carl. This poor guy is going away with nothing more than he came in with, a big roll of the dice unknown. Listen to the end of the mpeg and you will hear the noise go away at an idle, I stand fast with a stuck valve or valves. Take the cheap way out on the further diagnosis before tearing it down, remove the valve cover and observe the valve action.

I can take the cover off and get a better recording today or tomorrow. I really appreciate everyone's input.

Sorry for the following.

There's a mathematical process called the Fourier transform which takes "noise" and determines all of the individual frequencies and intensities which give rise to the "noise." Has there ever been this kind of analysis of engine "noise?"

Again, I apologize.

i wrote a paper on the feasibility of analyzing the sound of modern engines via FFT and weighted time domain to see if we could compare the known healthy sound to the bad sounds and diagnose problems, there is a lot of promising results, however seeding the database to make it useful out the gate is a non trivial problem.

turns out it's sorta already used a bit, sensors on fancy industrial equipment are placed near major bearings and if the computer begins to detect too much correlated vibrations to shaft RPM and machine load it will flag the operators that a bearing should be replaced before it actually fails, neat.

i used an FFT app on my laptop once to prove to my land lord that his refrigerator in my apartment was making an insane high pitched noise that i could hear but he couldn't hear.
my friends even complained as soon as they walked in my door.
a nice big spike at about 18-19KHz, i don't recall specifically how high it was, but it was way up there near the limit of people perception, it was modal as well, depending on where you placed your head in the kitchen it would be louder or not noticeable.
i could make the big spike on the computer FFT go away by unplugging the fridge
with this evidence, he replaced the fridge for me, that was the nicest thing he ever did for me, then he wanted to increase rent by 17% the next year so i moved out

anyway, just record the sound of your engine and upload it, maybe we can all take turns running it through different analyzers
-s

Perhaps the previous 2 replies (mine included) can start (and end?) a new thread. I love this stuff and used FFT with NMR (MRI for molecules).

Well, this could be fun (not for bigfunsixone, perhaps )

So far, we have the following teams in the 2019 Stovebolt Name That Noise Championship:

1. Team Apachefiend -- Exhaust Leak (Needs more specificity to differentiate between you and Team Two)
2. Team Lightholder's Dad -- Exhaust manifold Leak (Unless you want to join Apachefiend's team ...)
3. Team SStock -- Bad/sticky Valve
4. Team SimS -- Piston/rod/wrist pin
5. Team Jerry -- Main Bearing

Not too late for new entries. Once BigFun begins analysis and starts eliminations, then entries will be closed. As corporate sponsor, I will figure out a suitable prize for the winning team.


John

Popping the popcorn right now!

What about the three higher math posters - they might want to start another thread, and include Chebyshev polynomials in their musings (probably in the HiPo Shop forum)?

I'm going with rod bearing.
If it was mine, that engine would get pulled and a full rebuild.
Also, Jerry would be my online advisor for any issues I may run in to.
Put this down as the Heartland Team entry!

Don

Don, Team SimS already called that one. You can join with them if you like or ask them to grant you the rod bearing specifically. For extra points, you could specify which rod.

Broken rocker shaft.🛠

Tuts59 respectfully asks permission to join Team Jerry, I believe it is a Main Bearing as well (rear main specifically for extra points.)

Troubleshooting 101.
Start with the easy to test components.
Pulling a valve cover qualifies as easy.

OK Grand Pooh Bear.
My Heartland Bolter vote is for the #5 or #6 rod bearing.
SimS is too wide open to join that team so I want to enter our own precise entry.
A 3' piece of 1/2 inch wood dowel, will tell you what cylinder it's on.

Don

If it is a main bearing, loading it at a low RPM will bring it out pretty clearly.

I think the high tech approaches that were mentioned are probably in use these days on new equipment where the expected sounds are known and don't deviate too much. I know auto engineers can use sensors to nail down noises and the exact timing as to which cylinder and during which part of the cycle it is happening,.

If I win, I will make my early donation to the stovebolt forum, still sounds like air and exhaust mixing (sticky valve bad cam)but Jerry is an oak. I'd like to hear what 235 Dave has to say

Timing is too advanced.....

New Teams!! But I think we need a ruling on Team sstock -- can "bad/sticky valve" be the same as "bad cam" or are those two separate issues? If two separate issues, we can only have one entry per team.

1. Team Apachefiend -- Exhaust Leak (Needs more specificity to differentiate between you and Team Two)
2. Team Lightholder's Dad -- Exhaust manifold Leak (Unless you want to join Apachefiend's team ...)
3. Team SStock -- Bad/sticky Valve
4. Team SimS -- Piston/rod/wrist pin
5. Team Jerry -- Main Bearing (Tuts59 and I are with Jerry)
6. Team Volfandt -- Timing
7. Team Heartland -- #5 or #6 Rod Bearing
8. Team Martin -- Rocker Shaft

Have you removed 1 spark plug wire at a time with the engine running? If it is a rod bearing or piston slap the noise won't be as pronounced. Did you take a compression check?

Rick

OK, guys- - - -I've been listening to engine noises for almost 60 years. Not being there leaning over the fender makes this one a little challenging, but my opinion hasn't changed. Here's why:

The hard-sounding BUMP-BUMP-BUMP as the engine is accelerating, then leveling off and almost going away as the load goes away is classic main bearing symptoms. The crankshaft is bouncing up and down on the mains (particularly the rear with the inertia of the flywheel and clutch) like a sledgehammer. A cracked piston skirt causes a somewhat similar noise, but not as heavy or as distinct as a main bearing. This one's definitely a main. Pulling spark plug wires one at a time can isolate a bad piston- - - -it won't change a main bearing noise.

Rod knocks happen on a "float" as the engine accelerates and the speed levels off- - - -the loose bearing hammers up and down on the crankshaft journal because of excessive clearance and/or crankshaft wear. Rods make a light to moderate RATTLE-RATTLE-RATTLE noise, much faster than a main bearing knock. If several rods are involved, the frequency of the noise is quite rapid.

Valve lifter and rocker arm noises happen at a lower frequency than connecting rod or main bearing noises- - - - -the camshaft turns at half crankshaft speed.

Now- - - - -pull that engine and tear it down while it's still rebuildable, or carry a big basket around to haul the parts home when it starts chucking bits and pieces out the side of the block!
Jerry

To me it sounds like it is popping back through the carb.

Hmmm. So are you recommending taking off the valve cover, or pull the engine for a complete rebuild?
We may need to lobby for the creation of a New Team.
We can call it the: "Take Off The Valve Cover" team.
Carl

You yahoo's do realize, that BigFunSixOne, just joined the Stovebolt Garage 5 days ago.
If he was in the Heartland, we would be lining up a team to help him yank and rebuild that motor.
Jerry would be on call for advice.
Hope we don't scare him off!

Don

He was lurking yesterday PM but he hasn’t posted any updates. Wonder if he’s in cahoots with Milliman until we all get frustrated with the lack of answers.🤪

That would be pretty funny if that ends up being the case, lol.

Yes. We need to do something about that trouble-making Milligan guy.

Dude, like ...What EVUR

Do you guys know what a woman means, when she says "What EVURRR!"?
I can't post the meaning, cause this is a family site.

Don

Trust me, I resemble that remark.