Each September, the Alfa Romeo Owners of Oregon puts on the “Red Duetto Tour.”

Hosted by Fred and Lisa McNabb, the entry requirements are simple: You must be driving a 1966-69 “longtail” Alfa spider, and it has to be red.

Before I bought my red Duetto, I recall asking Fred if I would be allowed to go on the tour if I bought a Duetto of a different color. “Yes, of course” he replied. “You would be allowed but your car wouldn’t.”

As a consequence of being featured in “The Graduate,” the longtail spiders may be the most recognizable Alfas of all time.

Strictly speaking, only those spiders built in 1966 and 1967 with 1600-cc Weber-carbureted engines are called Duettos. In the US, due to Alfa’s inability to meet smog and safety regulation, there was no 1968 model year. A few were imported to Canada with carbureted 1750-cc engines.

In 1969, to meet emissions requirements, Alfa introduced the Spica fuel injection system on a 1750-cc engine. These cars were badged as “Injected Spiders” (inezione) rather than Duettos.

In the spirit of inclusiveness — so long as your spider is red and has a long tail — the McNabbs refer to all longtails from 1966 to 1969 as  “Duettos.”

The SCM Duetto still has its original 1600-engine and 4.5 rear axle. Local specialist Nasko rebuilt the suspension, fitting Rugh springs and his sway bar. I have driven it to Monterey twice.

My pilot for the day was Cindy Banzer, president of the national Alfa Romeo Owners’ Club and co-founder of the Alfa Romeo Market Letter. SCM car wrangler Neil D’Autremont prepped our 1967 Duetto. At 9 am on a bright fall day, she picked me up from my downtown condo.

We headed north along the Columbia River to Scappoose, where we joined four other red Duettos. The number of cars varies from year to year, with sometimes as many as eleven participating.

Every year when I participate in this tour, I feel as if I have entered a magic land full of nothing but red Alfa round tails. There were stretches were I was looking at four Duettos ahead of me on curving two-lane roads.

The tour took us on Oregon Highway through Vernonia, then onto Highway 26 where we experienced the only equipment malfunction of the day.

The battery cable came loose on Dave and Colleen Rugh’s Duetto and managed to contact and melt and break the threaded carburetor linkage rod that goes from above the Webers to the bellcrank below them.

Rugh, an innovative engineer, used a zip tie to replace the throttle rod, and then tied two shoe laces together and ran them from the zip tie through the firewall. He was then able to operate the throttle by pulling on the shoe laces.

Don’t try that on a Tesla.

From Highway 26 we took Highway 53 to Tillamook and Oceanside.  Lunch was at Roseanne’s — a quaint, family-owned restaurant. I had fresh sturgeon with mango sauce. Dessert was a medley of fresh Oregon berries with ice cream.

211 miles later and we were home. The Duetto performed flawlessly, the engine turning an effortless 3,500 rpm at 70 mph.

I have long felt that the Duetto represents the high point of pre-emissions Alfa spiders. It has stunning lines that get better with age. As well as enough performance to be comfortable on today’s freeways, and nimble on two-lane roads.

If you’ve got a red Duetto, mark next September on your calendar. It’ll be a day you’ll remember.