Mulholland. In my group, the transition from racing on the straight, flat, streets of the Valley to curvy canyon roads started taking place around 1977. New factory stock cars weren't too quick anymore, so maybe you could have fun twisting the Gs in that new Oldsmobile-403-engined Trans Am of yours. Mikey will race you in you in his mom's powder-blue Mustang II. (Not as exciting as watching a Pro Stocker come off an enclosed trailer and run for $500, then go back into the trailer and disappear) but it was funny to watch the first couple of squirrels, each night, running out of talent in a corner.
There was a movie called "King of the Mountain" or something like that, which pitted a guy in a Porsche against some muscle cars. I'm going strictly by memory here, so I could be wrong about some of the details. The film was a low budget flick with several gag-worthy parts, but it got my pals and I to thinking about trying the canyon stuff too. In years previous, some of the COCOA guys had already explored those turns and started buying 911s and BMW 2002 tii to have fun with up there.
Here's a good article about racing on Mulholland from 1970s and earlier.
https://www.motortrend.com/features/the-ghosts-on-mulholland-drive/I enjoyed both kinds of illegal competition, and if you're ever driven at high speed along Decker Cyn, from PCH in Malibu connecting to Mulholland and onto Laurel Canyon (careful, Mulholland was not paved in sections, back then) you'll probably have just gotten a new speed addiction. I'd have to Google Maps it, but I'd guess the total run was bout 25-30 miles.
Those balls-out midnight runs became standard protocol for us (helming magazine test cars, as well as our own machines) most any night of the week. Usually zero traffic, great straights and corners, and the occasional azz-pucker from a deer jumping into your path. These runs tested every moving part of your car, including the ash tray hinges that rattled loose from the massive 4-axis g-forces.
Actually, there were many sections of the road where charging 80-100 mph into a dip could reward you with big air, or propel you off a cliff. So, make that 5-axis (axes?) We quickly started improving our cars' brakes, tires, suspensions, cooling systems, headlights, and replacing 4.11 and 4.56 street racing gears with higher-speed-friendly 3.50s, etc.
We only saw a cop ONE time. He was going home (our summation) on his Sheriff-issue bike and we fortunately? magically? had just slowed down to legal speeds as he came around a corner, in our direction. After that, we spaced out the cars in our group to no closer than a quarter-mile apart. Cheapo $99 Burt-Reynolds-approved CB radios kept us out of the way of most trouble. But, no satin jackets allowed.
There's an old falling-over sign-post (still there as of three years ago) at the intersection of Decker and Topanga Cyn, where we'd always stop and scrawl our ETs (from PCH to there) onto the post.
We did keep going to Van Nuys Bl on Wednesdays, and expanded our street-racing map to include Westchester, El Segundo (with the awesome 6-lane-wide Pershing Dr behind LAX) and Manhattan Beach. Manhattan usually had the best-looking girls. But, their cops would write you for 1 mph over. After we each got one of those friendly court summons we stopped venturing further south than LAX.
I just got a neat idea for a new thread. Watch for that post in 5,4,3,2...