My 70 396 recently developed a rattling noise that occurs on deceleration. The motor was at low idle so I adjusted the timing to 10 degrees and adjusted the idle screw to around 800 rpms. The rattle did not go away and when I reset the idle speed the car runs choppy and has trouble accelerating. Also I tightened the rockers nuts and none of these fixes have helped but have made the problem worse. I have limited knowledge of cars but would like to attempt to correct this myself if possible. The car is all original with 81,000 miles. The rattle or clattering is on the top side of the engine. Any advice is greatly appreciated. Thanks.

[This message has been edited by Sou023 (edited 06-09-2002).]

A guess is you may have a hydraulic lifter either on the way out or is out.

Just a guess as I can't hear it from where I am sitting. http://www.chevelles.com/forum/smile.gif

Deon

<BLOCKQUOTE>quote:</font><HR>Originally posted by Sou023:
My 70 396 recently developed a rattling noise that occurs on deceleration. The motor was at low idle so I adjusted the timing to 10 degrees and adjusted the idle screw to around 800 rpms. The rattle did not go away and when I reset the idle speed the car runs choppy and has trouble accelerating. Also I tightened the rockers nuts and none of these fixes have helped but have made the problem worse. I have limited knowledge of cars but would like to attempt to correct this myself if possible. The car is all original with 81,000 miles. The rattle or clattering is on the top side of the engine. Any advice is greatly appreciated. Thanks.

[This message has been edited by Sou023 (edited 06-09-2002).]<HR></BLOCKQUOTE>

#1. hook up a universal vacum gauge, and monitor the reading each time you short out a cylinder.

#2. Vacum reading will drop very LITTLE when shorting out a weak or dead cylinder.

#3. Remove valve cover on the side of the weak or dead cyliner, and look for either a bent push rod, a worn rocker arm, a broken(inner) valve spring, or a broken spring in the lifter.