Knocking/Clattering sound at 2500 rpm

[paulw]

I've got my 200ci/automatic high mileage '68 Mustang running pretty good lately. But I hear a clattering sound when the motor hits about 2300-2500 rpm. It doesn't sound like knocking/pinging. I put in premium gas and the noise was still there. It does it both when I hit about 65-70 mph on the freeway or if I'm in parked in neutral. It goes away when I let up on the accelerator. What is it?

paulw
1968 6cyl Mustang coupe
1969 351W Mustang GT conv.

 

[spikeomatic]

take a 1"x1" wooden stick about 3 feet long and put it to your ear move the other end of stick to different locals right on the motor while motor is clattering listen to try and pinpoint it.will be louder when you find it could be a loose torqconverter bolt? stay clear of the moving fan blades

 

[JackFish]

Check for loose exhaust manifold bolts.
I've had to re-tighten mine a couple of times.

 

[MPGmustang]

It can be the starter gear tore up, mine did and was still able to start till the rest fell off ... check to see if your starter is loose

 

[MustangSix]

High mileage? Fairly silent when cold, but noise shows up a speed or after high speed? Very likely a combination of worn lifters, pushrods, and rockers.