Hello I need help diagnosing a tapping sound> does not start until engine is up to temp around 160 on gauge.seems to be coming from driver side down low on engine. its a 360 in an f250 dual exhaust. Im thinking exhaust leak any other thoughts? thanks

 

If the exhaust was leaking, then smoke would be rising from where the exhaust manifold and the pipe(s) connect. Gut feeling is that a rod or piston is tapping the block, but if it doesnt start when you start up, then im not entirly sure.

 

Hmm check fuel pump it's a common problem when it gets tired of doing it job, put a long wood dowel or a long handle screw driver on the pump and up against your ear to detect if noise is coming from it.. Not it try removing spark plug one at a time while motor is running. If a rod you'll notice a change in knocking sound to isolate which is the problem..my 2cents
orich

 

yea have not had a chance to try the dowel,hose,stethoscope deal yet thanks for tips i will check it out

 

I had one so bad I though was a rod bearing I pulled the pan and found zip loose.
pulled the pump and the arm was about to fall out. I would have bet money it was a rod and lost!..so check it...orich

 

Picked up a HFT stethescope tapping was loudest when I placed it on top of fuel pump ,replaced pump still tapping, would this be because the sound of whatever is tapping is transfering through fuel pump? not familiar with fe motors is pump driven off cam eccentric like on a small block? im at a loss as to what could be tapping.and if it a major concern or just drive it last two small blocks i had all had slight valve train noise and the 170 in my econoline is noisy too but this is a very noticable tap. thanks

 

Could it be a sticking exhaust valve?
I have the same knocking sound as you but on a 69 F-250 and in my case, it was the #8 cylinder exhaust valve....it is sticked and it would not open as it should.

 

A vacuum test would detect this as with a fluttering movement on the meter. But if a compression check shows the psi to be way off on some cylinders due to burnt seats will show a fluttering with popping back through the carb under heavy load...
PS is it a taping or a deep knocking which can come from the rods or the fuel pump are hard some time s to figure out if you have a front rod that's bad...A piston pin makes a double tap if I remember right..
..orich

 

61eline, Orich has it covered good, It is too bad we cannot actually hear the noise . I once had a 390 that would make a tapping sound that turned out to be a worn valve guide , the noise was really hard to pin down. If I would rev it the noise would go away, then gradually come back at idle. This was in a 64 XL which was my own car. I pulled the heads and had the guides sleeved, no more noise. 18 months later the noise came back acting the same , this time it was the fuel pump just like Orich described earlier. Have you tried pulling each plug wire to see if the noise changes? Also , this is along shot but easy, take off the air cleaner and warm up the engine until the noise starts, gradually squirt atf into the carbureator ,if it is an exhaust leak you will see the smoke , also good for killing mosquitos. Kenny Nunez

 

If the sound is actually at the Fuel Pump, It might be the Fuel Pump eccentric is loose on the end of the cam. Worth taking off the pump and sticking your finger in there. See if you can move the eccentric with your finger.

 

Sounds like lifters to me. Do you have an oil pressure reading when warm?

 

yes oil pressure is good 20psi at idle around 40 at speed.tapping starts as soon as it hits 160f on the temp gauge.once the truck sits over night, no tapping on start up starts tapping again at 160? gonna try pulling plug wires one at a time next. see if i can pinpoint it to a certain cylinder.

 

Oil pressure is always higher when cold.

 

You may have a cracked piston too, most times you won't hear it when cold, only after warming up.