Oldsmobile 307 Engine - Analyze This!

When brothers Dale and Glenn Robinson decided to take up the gauntlet and enter the 2008 Engine Masters Challenge, they knew they needed every advantage they could get. They had to know all of the rules inside and out, and create a combination that could wow the crowd and still stay within budget. Their approach to building this little 307-based Olds mirrored their team name, Robinson Analytical.

Dale has been bracket racing with Olds power for a number of years, and is comfortable enough with the architecture of the engine that he knew its weaknesses and strengths. Talking with Dale, it is clear that he's a levelheaded player, and his philosophy was to break down the engine building process into two distinct focus groups: weaknesses and strengths. This, he figured rightly, would be the best way to approach the build.

The Robinsons started their analysis with a $50 core engine from an '84 Toronado. A little digging tells us that the 307 engines were popular throughout the whole GM family. All of the BOP and Chevy passenger cars received versions of the 307 for their mid- and fullsize cars from 1980 to 1990. Most Olds engines have the cubic inches cast into the side of the block, though the 307 has a casting of a 5.0 liter on the block. If you are looking for one in the junkyard and you spot a two-barrel carbureted V-8, keep on looking, as all 307s used a four-barrel Quadrajet. In fact, the 307 was the last passenger car offered with a carburetor in the United States (except some Crown Vic Police Interceptors, as we're sure someone will scream out).

For every Olds lover, the biggest struggle with the engine isn't necessarily making power, but keeping the engine intact. The 307, like the 403 and other Olds blocks, uses an open main-webbing design that saved the powerplants a good amount of weight, and GM a good amount of coin, but sacrificed structural strength. With a talent for machine work and an eye for details, Dale got started remedying this issue by building a structural support, connecting all of the mains to the block. He says: "I used a piece of 1018 flat bar with some blocks to connect it to the halo girdle, and I machined the caps and that's it. I bought the halo off J&S Machine and connected it all together." He used a set of spacer blocks between the J&S halo and the main girdle and used brass shim stock to set the preload to what he wanted. Finally, 3/8-inch Allen-head capscrews fasten the homebuilt girdle to the pan rail. In essence, he built a super-sized main girdle for the block. The beefed-up support had a secondary feature that helped move the oil pan further from the windage whipping around, thus better controlling the oil.

With a combination of homemade...        read full caption With a combination of homemade and purchased parts, Dale was able to make the sturdiest 307 Olds bottom end known to man. Unlike other girdle setups that require special oil pan ends, he says this used the stock pan ends with no problems and fit around the oil pump like a glove.	The only mods to the oil pan...        read full caption The only mods to the oil pan were holes to accommodate the 3/8-inch Allen bolt heads poking up from the girdle.	After several hours with a...        read full caption After several hours with a grinder, the factory-forged 330 crank looked and performed more like some of the high-dollar cranks, but at a fraction of the cost. ARP 2000 rod bolts like the ones seen here come as standard fare on the Eagle featherweight rods.
The design staff at Olds was...        read full caption The design staff at Olds was fickle with cam and lifter designs, changing lifter angle and bore sizes several times over the years. The large diameter of the mid-'80s 307 lifters makes them desirable. To take full advantage of their size, however, requires having dedicated cam lobes designed at over a thousand dollars a pop for intake and exhaust. Using the Mopar lobes gets you 90 percent of the way there, and saves a ton of cash.	Glenn points out the weld...        read full caption Glenn points out the weld line where the original port ended and the Robinson-designed port begins. The entire center section between the two center runners was added and cleaned up enough that it looks like the factory cast it that way.	Like most engine builders,...        read full caption Like most engine builders, the Robinson Analytical team found easy power by using an electric water pump like the one here from Meziere. The split timing cover allows easy access for cam timing changes.