Is the distributor in good nick? If the centrifugal advance is stuck, you might have the advance right for idle but way retarded at higher revs which would give poor economy and performance. Vacuum advance is also important for economy. Here are a couple of checks:
Take the dizzy cap off and disconnect vacuum advance hose. Sucking on it, does the advance plate move, does the vacuum hold, and does the plate return when you release the vacuum?
Put the dizzy cap back on, but block off the vacuum advance. Run the engine with the timing light. Watch the marks as you raise the revs from idle to about 2500. You should see the mark move smoothly towards the left (advance) as the revs increase.
Have fun,
Rob.
Take the dizzy cap off and disconnect vacuum advance hose. Sucking on it, does the advance plate move, does the vacuum hold, and does the plate return when you release the vacuum?
Put the dizzy cap back on, but block off the vacuum advance. Run the engine with the timing light. Watch the marks as you raise the revs from idle to about 2500. You should see the mark move smoothly towards the left (advance) as the revs increase.
Have fun,
Rob.