# Help me diagnose a engine knock please?



## billthedog (Apr 7, 2010)

My little 1974 B-210 Hatchback A13 engine is making a sound that I have not heard before!

The sound is most noticeable at idle, shorting individual plugs does not change it, the sound can't be heard while driving.
Nothing unusual is heard at the timing cover or at either side of the block at the mid cylinder areas, nor at the valve train.

Compression is good, drives just fine, but the new sound has me "spooked" because I don't know what it is!

The sound was recorded by pressing a tiny amplified microphone to various places on the engine block with the engine warm and idling.
The sound is the loudest at the seam between the oil pan and the lower block about 4" from the rear of the block, distributor side, next to the starter.

A link to the 50 second sound clip in mp3 format is below, it will play when you click it
(private secured server)
Please note that on the second half of the sound clip you can hear the knock better because I moved the #3 plug wire away form the microphone cord.

Notice the knock changes pitch (like a xylophone with wooden bars) ???

http://67.55.0.15/images/B210.mp3


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