I have a 67 bird with 400. When car warms up I get a strange sound from front of engine. Ive replaced smog pump,water pump, and clutch fan. Sounds like a loose air cleaner lid, gets worse as car warms up sound goes away when accelarating.Could it possibly be timing chain or harmonic balancer????? Please help getting frustrated

Do you have the stock air cleaner with the metal door that lets in warm air from the exhaust manifold shroud? If so, it could it be metal door flapping in the air stream and it only does it when the engine is warm and the door is in the right position.

definitely motor related, I forgot to mention car makes this sound when in Park. Also air cleaner does not have a flap. sound is more noticeable when engine is shutting down

maybe try checking the heat riser if you have stock exhaust manifolds.

If you have an automatic, loose converter bolts will make that noise. You sure it's coming from the front of the engine?

I second Scott with the heat riser valve in the exhaust manifold, if you have one. Many people wired them open back in the 60's to stop that rattle. In mid-year '68 I believe they were discontinued in our cars.

Pauly,
I think it's the timing chain. It was making that noise when I owned it and I thought it was the smog pump. If I remember the history correctly, the engine has the original chain. It could be slapping the cover. If it's not the exhaust manifold flapper or the air cleaner flapper I would go for the chain.
Jim

I have a funny noise comming from the front of my car. took me awhile to find it. I took the belts off and for trouble shooting and when I put them back on I saw that one of my 4 crank pulley bolts was missing and the others were loose.

Thanks for the advice I guess its off to the garage I have a feeling its the timing chain will let you know thanks again

The fuel pump eccentric can make similar noise; likewise, a weak spring in the fuel pump can make similar noise. Such noise is typical of a Pontiac engine, the reason I switched to an electric pump.

Oh yeah, one way to make 100% sure whether or not it's fuel pump eccentric related would be to remove the fuel pump, disconnect/block the fuel line, and rig up a pony bottle of gas to the carburator. Beats the heck out of tearing it down on a hit-or-miss guess, and it narrows down the possibilities.