1939 Ford flathead rattle
 

My 1939 Ford Deluxe Convertible flathead was rebuilt in 2011 and only driven about 300-400 miles since as I was abroad. After sitting for 7 years I drove the car last September about 60 miles and car ran great. Now I started the car and it started fine and runs good but there is a rattle at rpm slightly over idle. Sounds to me like it comes from the manifold and maybe one oil deflector has popped off? Rattle is more like a piece of sheet metal loose than anything else. With higher rpm the rattle is gone but returns when rpm drops and disapears with idle. Does my diagnose sound right? Any ideas?

Re: 1939 Ford flathead rattle
 

If you decide to remove the intake and look inside, please let us know what you find. Your
oil deflector theory sounds like a good possibility.

Re: 1939 Ford flathead rattle
 

The tube in the bottom of the fuel pump stand could have dropped out of the stand if it was too short.

Re: 1939 Ford flathead rattle
 

A rattle or vibration that is due to resonation is tough to locate. Since it is one that seems to be like sheet metal, it probably is not inside the engine. If you haven't already, have someone rev the engine as you check under the hood. Just be careful!

Re: 1939 Ford flathead rattle
 

Most everything can resonate if the right frequency of vibration is induced. There have been a few problem spots on some of the helicopters I work on where certain parts will resonate at normal use rpm settings. The only way I have found that works is to change the tune of the offending part by adding weigh to it. This changes the frequency of vibration that will make it start to resonate which is, in effect, detuning the the part. It's usually long spans of sheet metal or tubing that have only a light duty amount of support in the span. On the helicopters, it's generally one of the stabilizers that has a trailing edge tab or one of the landing gear tubes. On a car it could be an inner fender panel or a fan shroud. If the hood has any oil canning from previous damage that stretched the metal there then it can resonate too. In cases like that, shrinking the metal will tighten it back up since adding weights would likely be visible. A loose air filter or horn trumpet might also resonate. Loose parts just need to be tightened back up in some way.

If it is something loose inside the engine, it should rattle all the time at any rpm setting.

Re: 1939 Ford flathead rattle
 

As others have said, check that tube running down the center of the breather. Ask me how I learned about this issue...

Re: 1939 Ford flathead rattle
 

use a listening stick. Be careful

Re: 1939 Ford flathead rattle
 

I had a loose muffler baffle vibrate at certain RPMs. Had to run it on a lift to find it.

Re: 1939 Ford flathead rattle
 

On my avatar I had a sheet metal rattle just above idle rpms . Turned out to be the bottom of the inner fender just below the louvers had about 1/32" clearance from the frame. It took me about a year to find it-about drove me crazy.

Re: 1939 Ford flathead rattle
 

Thanks for the replies guys. It does seem difficult pinpointing the noise. The fact that you cannot hear it all the time would suggest something outside the motor I guess which is good news. I need to get under the car while the engine is running WITH RATTLE rpm to investigate, I have my dad’s old stetoscope and will listen to intake as well but prefer not to pull it yet though it is not such a big job. Maybe I’ll drain the oil just incase to see if there are any loose particle which I doubt. Any additional ideas welcome.

Re: 1939 Ford flathead rattle
 

What was the fix?

Re: 1939 Ford flathead rattle
 

You can JB weld it back into the stand. Or find another stand that the hole is tight and the tube is intact.

Re: 1939 Ford flathead rattle
 

I just tack-welded it back in place. A simple fix and it’s NEVER coming loose again.

Re: 1939 Ford flathead rattle
 

I have now listened to the rattle and driven the car a bit. Definitely not from the engine which runs very smooth. I would say clutch area, throw out bearing maybe? It has lessened with driving and does not seem to occur when car is warm after some driving. Engine pans and exhaust are tight, so is fuel pump rod bracket.