1963 Carter AFB 3589S, similar to what was used on the R1 Avanti . Things to note are Base plate shows where the PCV line was attached to the rear of the baseplate, inducing occasional plug fouling/ color of the rear barrel throttleplate shows lack of use (darktan) causing buildup of oil sludge. When WOT is achieved, this sludge pours into the manifold, gets thinned by rich fuel flow and affects the rear cylinders spark plugs.. Later models of this carb connect PCV to front port & block the rear

The Top carb picture shows the vent holes drilled into the top cover, above each of the 4 venturi pipes. These holes facilitate equalizing fuel level and are NOT found on the AFB used on the R2 series engines. R2 engine carbs are sealed in this area (no holes at all)

Pictures of a Carter AFB (3589s) vented AFB Carburator. Used on the R1