Throttle Body vs Carb Spacer

[Dead Parrot]

Here is a thread on timing: http://67-72chevytrucks.com/vboard/s...d.php?t=274806

Is your truck still covered under any kind of emissions testing/inspections?
Verify that the following still work:
Exhaust heat riser valve
THERMAC system
EGR(if equipped)
PVC system, PVC valve and filter are cheap
Both mechanical and vacuum advance

If they are several years old or age unknown, consider new cap, rotor, plug wires and plugs. While the cap is off, repair or replace any broken advance parts as needed.
Replace any cracked or hard vacuum hoses.

Sounds like a lot but if you do your "how to" research first, then buy or borrow any needed tools should take less then a day to fully check things out.

Trying to tune an engine when these systems are not working properly is an exercise in frustration.