1979 Chevy Blazer

Hi there,

As you can imagine, second guessing a noise with out hearing it first is rather hard. Remove a plug lead or injector lead and run engine, listen for noise, if you hit the suspect cylinder the noise will diminish if it is a pin or big end bearing, as the pressure in the cylinder is far less so ids the stress on the faulty bearing, if it is there all the time and in sync with crank shaft revs, normally a main, if 1/2 or less crank speed big end, Regardless if you have an internal knock, it wont go away on it's own, so check the oil pressure just in case there is a problem there first.

Mark (mhpautos)