For April, Roadkill has decied to spotlight a few V8s with 400 or more cubic inches to match the dates this month, like the AMC 401 on 4/01. While the 401 is regarded as one of the pinnacles of AMC engineering, the Oldsmobile 403 is notable primarily for its obscurity. Nevertheless, we were pretty excited to hear from RK Nation member Amber Dennis about the 403-powered 1978 Pontiac Trans Am Gold Edition project she is working on with her husband Cory in Madrid, Iowa.
Before we get to the Trans Am, the 403 is worth a bit of explaining. When General Motors downsized its model lineup in 1977, the company also purged Oldsmobile of its famous big-block 455 cubic-inch V8. Needing a smaller engine to fill the top of the options sheet, GM took its tried and true Olds 350 and bored it to within millimeters of its life. The 403’s resulting 4.351-inch bore was the largest ever for any small-block V8 and with its relatively short stroke (3.385 inches), it might have been a rev-happy world beater.
Unfortunately, this was the Malaise Era when emissions equipment defeated most attempts at making real power. The 185 horsepower from the Olds 403 sounds meager—especially for a Trans Am—but few other contemporary engines were making more power from similar displacement. As for tuning, an Oldsmobile V8 tuning site suggests that the 403’s bottom end was ill-equipped to handle big horsepower, but the engine as a whole has potential for a wicked street machine. At least we know it will burn a bit of rubber in a G-Body Cutlass Calais.
So how did it end up in a Trans Am? Most people familiar with Trans Am will know that Pontiac used its own 400 cubic-inch V8 in the Disco-era Firebird. However, the Olds 403 replaced the 400 in California as the top engine option for what we assume to be smog-related reasons.
That makes this a very rare 403-powered Gold Edition Trans Am for Amber and Cory. One Pontiac site estimated that a bit more than 10 percent of the Gold Edition cars had the 403, which is a small subset of a small subset of Firebird production. The Gold Edition included gold “snowflake” wheels originally and a host of other special, primarily cosmetic options
When Amber and Cory were looking for a project (after binge-watching Roadkill, of course), they found this car on CraigsList that ticked all of the classic F-Body options: shaker-style hood, big engine, and T-Tops (Three out of four scientists recommend T-Tops on your Firebird, we remember hearing one time). They got it running with a new carb and ignition parts and while Amber says it has “some leaks here and there and some body work that needs to be done, she notes “it is a project car that him and I can do together.” We’re glad to see them fixing up one of the few cool pieces of Malaise Era history.
GM ended 403 production after the 1979 model year, opting to utilize smaller V8s as performance options in Oldsmobiles with the 231 V6 and dreaded diesel 350 as the economy options. That leaves the 403 as a curiosity for the most part, although you can still source speed parts or even complete rebuilds for reasonable money.