If it,s a manual trans. slow thw idle down a little. Check for vacuum leaks. The Monojet carb. can wallow out the gasket between the throttle body & fuel bowl. You usually can see it from the outside. The timing doesn,t effect that unless it,s way off. You can usually run 6-8 advance on those & it will run better. If it pings set it back a little. If your spark plug heat range is to hot it can cause that. If you can,t fix it get a idle selenoid from a 6 cyl. car with air. Hook it up to the ignition switch. Set the initial idle to about 500 & set it with the selenoid to 6-700. When you shut off the key the selenoid will let the throttle almost close.
