Mystery Engine Noise

[too fordy]

Here's an intersting problem for you gentlemen to help me diagnose...  - I have a 1973 240Z with a ford 2.3T motor ( Code Name: Too Fordy ) 

After the swap was complete, everything was great except for an RPM specific engine rattle. I recorded a video with good audio so you can hear what I hear. The noise is not present at idle and seems to disappear above 3k or so. 

Here's some background on the motor. 

* I have no idea how many miles were on it when purchased. 

* I replaced dizzy, cap, rotor, plugs, wires, tps, & fluids recently. 

* Compression test was performed today with the following results: Cyl 1: 165psi - Cly 2: 165psi - Cyl 3: 165psi - Cyl 4: 160psi 

* Value lash is within factory specs when checked with feeler gauge/ cam looks good and is without pitting or major imperfections. 

* When the oil pan was removed I found bearings that look normal and none stand out as being different from the rest. 

 

What is going on?? Here is a link to the video: 

 

 

 

 

 

Edited January 31, 2017 by too fordy

[DatsunZGuy]

For starters, I would invest in one of these:

http://www.harborfreight.com/catalogsearch/result?q=stethoscope

From the sound of it, there could be a loose component like a exhaust heat shield causing the noise.  I had a mystery rattle at around idle to about 2,000 rpm from the engine bay of my Honda.  It turned out to be the plastic grommet broke loose from the base of my hood prop rod that attached to the fender.

 

[7tooZ]

I thought it sounded like it could be an exhaust leak. Does it get less as it reaches full temp?


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[Mark Maras]

 A cheap stethoscope is a great tool but sometimes a bit short. A 3'-4' piece of garden hose (siphon hose) held to an ear will allow one to poke about without kissing a hot engine.