New season starts with a loud knocking noise

[zaugger]

Hey folks!

Still a relative newbie here. I winterized my 29, and after lubing the chasis and getting her ready for what might be spring in Minnesota, I was confronted by a pretty noticeable knock. You can hear it in the video link below. Any ideas would be much appreciated. Thanks!

Chris
https://youtube.com/shorts/1aPZUaB4dSM?feature=share

[nkaminar]

Check for an exhaust leak. Does not seem to be rods or mains.

[Marshall V. Daut]

Take off the fan belt and run the engine for a brief time. It may be a bearing going bad inside the generator, a dry bushing inside or even a water pump in need of lube. If the sound goes away without the fan belt in place, your suspects have been limited to the generator, water pump or a fan belt going bad. Also check the tightness of the crankshaft ratchet nut. Inspect the crankshaft pulley to ensure it is not breaking apart. The pulley is made of cast iron and will crack. It may be trying to warn you.
Marshall

[zaugger]

Thanks, guys! I'll give it a try!

[J Franklin]

A mechanics stethoscope comes in handy for weird noises, just keep away from moving parts! Removing the fan belt is a good first step and removes a bunch of noisemakers all at once. You should be able to run your engine for quite a while without overheating as it will thermosyphon.

[Benson]

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1. Might be an original steel two blade fan getting ready to explode !


2. Four blade steel fans usually have the rivets come loose and blade separates from the hub and make similar noises before the blade makes a large hole in the hood ... or your face if you happen to have your face too close while revving the engine!



Also many radiators have been destroyed this way!

[Herb Concord Ca]

Another suggestion, reverse the timing pin and hold it against the gear with the motor running see if the sound changes, if it does check the gear out it may be loose or warning out, If tis worn, replace with an Aluminum gear.

[CT Jack]

I agree with Herb. Slow you idle speed down and carefully insert the pin backwards. I experienced a similar problem and when I inserted the pin the knocking sound almost disappeared as I forced it against the timing gear. Replacing the gear is not difficult. I would use a metal gear and make certain it is properly torqued. If you have an original 2 bladed fan I recommend you replace it with an aluminum 2 bladed fan. Keep the original one as a souvenir or hang it on the wall in your garage.

[Sunny the Model A]

I agree on checking the timing gear also, but I think the fiber gear is better because it's there for a reason. Henry put the fiber gear on so if the cam or distributer ever developed a bind, it would shear off the teeth and protect the block. if the distributer ever bound up good, something will have to give, better put a fiber gear on it and save your heinie than have to shell out for a new block. There is my 2 cents

[katy]

Originally Posted by Sunny the Model A

Henry put the fiber gear on so if the cam or distributer ever developed a bind, it would shear off the teeth and protect the block.

First time I ever heard that story.

[Patrick L.]

A good time to check the cam gear with the timing pin is while the fan belt is off and the noise still exists.

[Benson]

Distributor bushing could need oiling.

[nkaminar]

To check for an exhaust leak, use piece of hose. Larger diameter is better than smaller diameter. Old garden hose works well. Hold one end to your good ear and move the other around the manifold when the engine is running.

To check for an internal knock, use a piece of wood dowel and hold one end to your thumb which is next to your ear and touch the other to various places on the engine. Don't stick the dowel in your ear but place your thumb between the end of the dowel and your ear. Use your good ear. Your thumb can be tight against your ear.

[zaugger]

So here’s a twist. Started it up, increased and decreased the idle, played with the spark advance, and no knock at all. Same as the last 2 times I took her out. Fine in the garage, but as I soon as I drive it I get the knock, and when I put it back in the garage at idle the knock remains? Any thoughts on THAT??

[Patrick L.]

Hmm, a puzzlement.

The above recommendations are good ones.

The noise needs to be located in order to be of more help.

One thing I didn't think was mentioned is the starter drive rattling against the flywheel ring gear.

[nkaminar]

Check the timing gear. If the thrust spring at the front that pushes against the cam is not strong enough the gear can move forward and make this sound. You can add a washer or two under the spring to increase the force. The sound can come and go.

You need to take the front cover off to make changes to the spring. It is easiest to remove the radiator. You have to remove the two large bolts for the front engine mount. The engine is balanced on the rear motor mounts so the front of the engine will not fall down when the two large bolts are removed. You do not have to pull the pulley but you can look at the pulley at the same time to see if it is broken. There are 4 bolts that come up from the pan into that front cover.

Before you do that you can take the side cover off to look at the gear. You do not have to remove the radiator to do that. See if you can move the gear forward with a screw driver or flat lever. Be careful not to damage the gear.

[katy]

Originally Posted by nkaminar

You need to take the front cover off to make changes to the spring. It is easiest to remove the radiator.

It's not necessary to remove the radiator to remove the timing gear (front) cover, removing the radiator entails a lot more work.

[tinkirk]

did you ever get this noise figured out?

[Ivan in southeast va.]

Sounds like a model a to me.