"Steve Lusardi" wrote in message
...
The key is low idle vacuum. You have a leak or you have lost index on the
balancer and TDC needs to be verified. Don't overlook the brake vacuum
booster, throttle shafts on the carb,PVC valve or EGR valve leakage.
Steve


if the idle is irregular the vacuum will be low, whether the irregularity is
due to ignition problems, valves, a leak, or something else. To me, at
least, on that vintage engine, the sound of the engine is very distinct if
it is fuel starved, or fuel rich, and it changes if the timing (ignition
timing) is off also. Of couse the descriptions here are text only and don't
include sound files, but here's my impression

lean - harsh sound
rich - soft labored sound
advanced - sharp stacatto sound
retarded - labored and weak sound

take a thin hose, hold one end near your ear and move the other end around
the manifold, carb, plugs, etc - listen and see if you hear leakage