Originally Posted by 60wag
The stock jetting worked well for my '84 60. The HAC system is primitive but works well enough to pass the test IF everything else is working. The problems that I had to deal with to pass emissions involved a non-functioning ABV. When this valve fails to function, the output of the air pump doesn't make it into the exhaust and the cat can't function. It is possible that your cat is shot as well. Also, the air pump may not be moving enough air. There are other emissions systems that can cause problems but most if he problems I have experienced have been related to the air injection and cataylst.
The 1980 emissions manual should be correct for your truck.
You want to be able to measure a temperature rise between the inlet and the outlet of the cat. You can fake the ABV to always deliver air to the exhaust pipe,( if the ABV is working). If theABV is toast, you can bypass it for the test. Once you have air going into the exhaust combined with unburnt fuel, the cat will get really hot if it is working.
I have a friend that is currently struggling and I think it's due to the ABV based on FSM tests. I have a laser temp reader if you need to borrow it (in SW Littleton), and it's helpful to have 2 people to do the FSM tests on the various bits.