The Stovebolt Site Forums The Shop Area Engine Shop Horrible Sound from my 261

My 261 has been giving me a sound for a while. I thought it was from the water pump which was going to be changed to Dave's repositioning adapter and new pump so I didn't worry. I decided to check that theory yesterday. I removed the fan belt and the sound persisted. Yikes!

The noise starts at about 1300 RPM and is gone at about 1700 RPM but maybe it's so high pitched only the dog can hear it. The sound is louder when placing a stethoscope end on the crankcase vent tube than the valve cover. More yikes!

Click for a video. What are your best bets for the source? Any other checks I can make?

Noise Starts at 1300 RPM
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Wally,
More than likely you need another harmonic balancer, I had one do the exact thing last year

Man oh man. Hard to tell from the video as it sounds more external than internal. Sounds like something has come loose and rubbing.

Check the free play on the clutch pedal. It sounds like you've got a throwout bearing that's running all the time and it's in the process of failing. You should have a minimum of 3/4-1" of free movement of the pedal before you start feeling the clutch begin to release. Do you have the proper pedal return spring on the clutch?
Jerry

I think the sound comes from the front of the engine. I crawled under the truck while Mrs. Wally gave it some gas (wheels very well blocked!) and the sound was not coming from the throwout bearing.

How does this type of harmonic balancer go bad? It's been on the 261 since 2004. When I increase the RPMs, it doesn't wobble, vibrate, etc. It stays spot on.

Can you replace a harmonic balancer while the engine is in the truck?

Thanks for your help!!

Here's a video with perhaps better sound.

Another Video w/Sound.
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Water pump bearing. ?

He said he removed the belt which took the water pump out of the picture and it still made noise.

Mike B

I'll 2nd the balancer. The rivets that attach the pulley to the back of the hub get loose & will eventually crank the pulley. The rubber will still look good which can fool you.

The engine will run with the balancer removed, also. I'm hearing a squeal from a tight main bearing that is about to lock up for some reason. Don't run it much more before you dig into things and find the source of the noise.
Jerry

I realize you say it sounds like its coming from the front of the engine, but that sounds like when the shield in front of the flywheel is rubbing the crank.

George

Oh how I dislike hearing one of these dependable old engine's having growing pains. In the past I have had harmonic balancer problems. Think of a toy top trying to spin with a weight on one side, now think about a large weight on the end of the crank shaft. This can cause all kind's of vibration sounds through the MAIN part of engine. Everyone is telling you problems that has happened to them or are aware. If Hotrod Lincoln is correct (he has never been wrong for me), you could have a serious problem with a main bearing. I would go with the simplest first then proceed to the next. Yup a throw out bearing or a piece of metal inside your flywheel pan can be nasty. Ask Hotrod Lincoln about the possible crank bearing issue. It is always best in possible serious internal situations to drop the oil pan. If metallic fleck's are present you have a solvable problem. Good luck. Let us know, that is how we learn. Doc.

I removed the flywheel shield. The sound (which starts at 1300 RPM and fades away at 1700 RPM with or w/o fan belt) doesn't come from back there.

I used a stethoscope along the block and head and it gets louder up front. The distributor doesn't given much sound (except some zapping noise). The fuel pump doesn't give much extra stethoscope sound either but I replaced it today anyway with no effect. Just hoping and praying.

My clutch pedal has about 3/4" free travel and then the spring is pretty strong, the way I like it.

The balancer is the next thing to consider or pull. I probably should change it anyway because I think the too large pulley diameter is the one that Dave does not suggest for his water pump adapter plate.

My two standby old-timer mechanics have firmly retired. There might be 1 or 2 others in town that I would trust to at least help with the diagnosis.

Doc, I also think these engines are sooo dependable but my 261 is at least the 3rd engine in my '48! The radiator frame was cut once and welded. Then it was cut and not rewelded. So I didn't leave that kind of engine removal history when I removed the 235 and dropped in the 261.

I'll keep in touch but I will be out of state for the next 3 weeks or so but please keep giving suggestions anyway. Thanks for your help!!

I'm just a new guy here. I am bringing a '37 back from 50 years of sitting in a barn and I'm no expert but I'm learning as I go.
I had a high pitch screech up front and a few drops of oil in the generator oil caps solved the problem.
It sounded a lot like your noise. I can't see in the video if you have a second belt running your generator.
Maybe I just got lucky.

Sound persists after removing the single fan belt. Thanks, though!!

Any updates Wally?

I just got back, Steve, and reunited with my '48. I have another video w/sound taken from inside the cab.

Sound from Inside Cab.

I've received good suggestions (above and other friends). I've already looked at some of them and gave the results above. I'll look at others in order of how easy the checking would be.
I will:

1. pull the valve cover and idle up the engine. The sound begins at 1300 RPM. Using a stethoscope, the sound is much louder on top of the crankcase vent tube than the valve cover but this only costs one gasket.
2. pull the harmonic balancer. Check it out and run the engine up to the 1300 RPM.
3. remove the timing gear cover and check for rubbing marks. I understand the timing gear can get a bit catywompous and rub on the cover if I understood correctly.
4. get back in touch with you guys!

Thanks for your help so far and into the future!

Unless the harmonic balancer slips forward on the crankshaft snout, there's virtually no way for the crankshaft gear to touch the timing cover, and I'm pretty sure the angle of the gear teeth and the rotation of the crankshaft will keep the cam gear pushed back against the thrust plate. Not saying it's impossible- - - -you might also find a chicken with lips one of these days! If there's a bunch of big dents in the timing cover, all bets are off, however!
Jerry

Try using a piece of broom handle about 3' long. Put one end on the engine (like you would the stethoscope) the other to your ear. You will be able to hear noises in the area you are touching and not picking up all the other noises like you would with the stethoscope.

Took off the valve cover and things look hunky dory. The noise comes from below the rockers, etc. and to the front.

Next in order would be to remove the harmonic balancer and see if the sound persists at accelerated idle (1300 RPM). I might also try to find a good engine man.

Any other more "minor" checks I could make?

Thanks!!!

I use a piece of 3/8" plastic tubing to listen. I can point the end and it is very directional.

I'll get some tubing.

How much oil should be coming out the little holes in the top of the rocker arms? Oil is definitely coming out all of them and overflowing the spring cap but it's much less than I thought. It has always idled very, very quietly but I was surprised to see how little oil came out there. Is it supposed to be a gusher?

Thanks!!

Just a dribble is correct.

X2. With the rocker arm down compressing the spring, the Dribble lubricates the rocker arm tip and the valve Tip, and as a coolant for the valve spring, lube for rotator caps if you have them. With the rocker arm up so to speak, valve closed, lubricates the adjuster ball and pushrod seat. If it spits, It’s likely spitting over the rocker arm and that is not What you want to see. Nice even dribble.

Good. Dribble it is.

I went a step further than a stethoscope to find a suspension problem on my car, and bought a Chassis Ear. It has 6 very sensitive clip on microphones plugged into a small 6 channel amplifier hooked up to headphones. You can switch between the microphones with a selector switch. With the microphones hooked up the front suspension I could hear the key turning the ignition switch, starter,every lifter, alternator, and everything else that moves. Figured out that if I started turning down the volume down, I could filter out all of the other noises to hear what was making the loudest noise I was looking for. It's tough to hold a screwdriver to your ear listening for a suspension noise driving down the road.

I got the damper off as discussed in separate thread. Removing Harmonic Balancer Thread. The sound remains while running up the idle for 3-4 seconds. Dang!

While cleaning up the timing gear case for removal I noticed what's in the picture. Two loose nuts on the front motor mount bolts. The engine was sitting on studs and not bolted down. Could this be the problem?

Nope. Sound persists after tightening up the bolts.

Next. Drop the pan, take off the timing gear cover, look around and get back to you.

I had an interesting sound from my original '40 216 . Eventually I pulled the timing cover etc . pics to show backlash in the gears compared to the replacement gear .

Oh, and I drilled out the oil feed pipe some , but I don't think that is likely to be an issue on your newer engine .

Jerry is correct that the crank rotation pushes the cam against the thrust plate , so , if its dry in there ???

I'm doing things in order of ease and not necessarily in order of likelihood of the problem. I'm running out of easy things to do.

Thanks, Dusty. Here's my 16-year old timing gears for comparison. I'd say they look pristine. I turned the flywheel and the gears looked great all around. I can't see any scrape marks there or on the inside of the cover.

I dropped the oil pan, of course, to get at those 2 bolts to the timing gear cover. Things look OK to my amateur eyes. There is a tiny, tiny bit of end play in the connecting rods (1/32" maybe) but I think you want some.

So, what do you suggest I do next?

This is gone on for a while so I'll put on the video/audio again.

Thanks!!!

Can a bad hydraulic lifter make that noise?

Also, in the above picture, there's a crimped copper tube between the gears. Is that supposed to drip oil? Any way to check that?

Yes oil should come out of the nozzle.
I have in the past put the pan on temporarily an run the engine to be sure oil was coming from the nozzle. If it is you may have a little oil spray to clean.
But unless you gave everything a good cleaning before the picture I suspect you aren’t getting oil there.

Unless it is a Canadian Pontiac 261, it would have mechanical lifters (unless someone changed to hydraulic lifters)?

So we know what we/you are working with, what is the Engine Serial number (stamped into the ledge in the block at the rear of the distributor)?

Tim, No number stamped on the flat to the rear of the distributor. Clean and smooth. I always thought that meant it was a replacement engine from the factory. I've seen numbers stamped there on other engines, like my previous 235, but there's nothing on this 261.

The number cast into the block is 3769925. A241 (Jan 24, 1961?) also cast.

When I put the final touches to what the engine guy rebuilt in 2004, I put in hydraulic lifters. This was 16 years ago and I'm remembering the block being drilled for hydraulics. Me? Remember??

Tim, perhaps I should offer the prize in the picture for the correct answer to my problem noise.

I just had my pre-sleep shot of George Dickel.

Find & Post here the following codes:
Head casting code
Head date casting code
Block casting code
Block date casting code

We will then be somewhat certain on the head and the block that you are working on?

Ed, I think for a noise test you could put some grease or maybe 90w on the gears and test run it.
I think the noise will go away.

Check to make sure that the bolts which hold the camshaft thrust plate to the block are in place. If they are missing, I would suspect it would make a noise like that as the flange if that bearing was free-spinning.
You access them through the holes in the camshaft. You will need to manually turn the engine over until the holes line up with the bots. I believe that they take a large Phillips head screwdriver.

To summarize:

Block: 3769925 A241 (Jan 24, 1961)
Head: 3836848 C40 (Mar 4, 1960. The holes were drilled in this 848 head.)

I take a considerable amount of time thinking before doing anything.

I would have dropped that front main bearing cap and inspected the bearing about two weeks ago!
Jerry

A lot of my time is spent floating flies on the Clark Fork, Bitterroot and Blackfoot Rivers and another not-to-be-named stream. They are all within a few miles of my house. When the going gets tough, the tough go fishing, right?

Thanks everyone. More on the truck later.

I hear garden hackle works well on streams like that! Dead drift from a spinning rod!
LOL!
Jerry

I caught 4 rainbow and 1 brown trout on 2 different mornings week before last in NM. We pan fried them along with some potatoes, added some broccoli, fresh lemon, ketchup and had two meals fit for a king. Caught 3 on worms and 1 on cheese from the bridge at the south end of our property.