Mustang MonthlyHow To Engine
How To Build A Better Boss 302 Engine
JGM Performance Engineering Shows How To Get More Horsepower From Ford's Trans-Am Powerplant
Sometimes we stumble onto engine projects in the darnedest ways. In this case, we have a Boss 302 that has been sitting around for more than a decade in at least four different machine shops, as well as in my garage. It's a good example of how not to plan and execute an engine project. The engine has been consuming more than its fair share of space lately, so it became a priority.
It belongs to Ron Bramlett of Mustangs Plus in Stockton, California. He initially wanted to build this engine for one of his race cars. After one of my visits to Mustangs Plus, Ron drove me and his Boss 302 engine to Los Angeles. We dropped it off at a local machine shop, which sleeved the block and did much of the machine work. I eventually hauled it to other machine shops where there were several false starts but no progress.
Most of the delays were rooted in hard-to-find parts. A Boss 302 engine isn't the same as the average 289/302. It has a four-bolt main block, a steel crank with a 3-inch stroke, and C3AE-style 289 rod forgings with broad shoulders and larger 3/8-inch bolts. Although the Boss 302 uses 351C head castings, they have different cooling passages. It also uses a unique dual-plane, high-rise intake manifold, which was an issue for us because we didn't have one.
When I told Jim Grubbs of JGM Performance Engineering about the engine, he offered to build it. He thoroughly inspected the C8FE Boss block and D0ZE head castings. Everything checked out. Our block had been successfully sleeved and remained leak tight. Jim measured the bores and pistons, concluding that the block needed needlepoint machining and blueprinting. Our Crower Sportsman rods were ready for inspection and massaging, and Ron's Scat crank with 3-inch stroke was sent to the balancer along with pistons, rings, bearings, rods, a 28-ounce Centerforce flywheel, and a Fluidampr harmonic balancer.
When you build an engine, whether it's a stocker or a high-revving screamer, blueprinting should always be done. Professional engine builders teach us that it's important to look at your engine and see things you've never seen before. Never install parts right out of the box; always inspect and massage them as necessary.