Mustang MonthlyHow To Engine
How To Rebuild A 289 Hi-Po Engine
In Part One Of A Two-Part Rebuild, JGM Motorsports Tears Down An Original 289 High Performance From A '66 Shelby GT350
I've known Jim Grubbs, Jeff Latimer, and Ryan Peart of JGM Motorsports for many years. We've built a lot of engines and had a lot of fun together. Most of what we build together are warmed-up, run-of-the-mill small- and big-block Ford V-8s. Once in a great while we do an overhead cam Modular V-8 or perhaps an inline-six stocker.
I was visiting JGM one afternoon when a factory original 289 High Performance engine arrived from an unmolested '66 Shelby GT350 fastback belonging to Rolo Malschafsky. At first, I was skeptical. Based on what I knew about vintage Shelbys, most were run hard and hung up wet; few of them retain their original 289 High Performance engine. If they do, then the engine has been torn apart and rebuilt with forged pistons, heavy-duty rods, hotter cams, and bigger valves. Rolo's 289 Hi-Po hadn't been apart since Shelby took charge of it at his Los Angeles Imperial Highway factory in 1965. It was like cracking open a time capsule.
When Jim Grubbs removed the Cobra valve covers, this engine possessed a nostalgic aroma from that period-specific crankcase odor consisting of tetraethyl lead deposits from high-octane fuel. The combustion chambers contained trace lead deposits from the days when five bucks would fill the Mustang's 16-gallon tank with Sunoco 260 or Union 76 high-octane fuel.
Being there for this engine's disassembly was an opportunity to take a closer look at how engines were originally assembled at Ford's Cleveland engine plant more than four decades ago. Head gasket technology was crude by today's standards-paper with fire rings to keep the squeeze inside. Imagine a rear main seal made of rope instead of neoprene with a lip. The cast-iron water pump had never been replaced. The valvesprings were still that blazing factory red. Even the neoprene rubber umbrella valve seals remained intact.
On top was the original Buddy Bar Cobra high-rise aluminum intake and 460-cfm Autolite 4100 carburetor, which was used with the '66 GT350's optional C4 automatic as opposed to the 715-cfm Holley found on engines with the four-speed. In front was its factory-installed Autolite dual-point distributor with phenolic-bushed ignition points that had obviously been there a long time. Amazingly, the contacts were clean and unburned. Down below was the original Carter fuel pump. All in all, Rolo's 289 was an amazing, well-preserved example of what Shelby and Ford did together from 1965 to 1966.
After tearing down the 289 and inspecting its parts for irregularities and abnormal wear, Jim studied what the engine has been doing for its service life. The first phase should always be clean-up, then inspection for cracks and other flaws before spending a fortune on machine work. Even though an engine is factory original, that doesn't mean all its parts are what they should be. Each and every part mandates close inspection and measurement.
Once we have established what's a keeper and what's a throwaway, it's time to begin machine work. If a 289 block has been rebuilt before, it has probably been bored to 4.030 inches or 0.030-inch oversize. Although some builders don't mind going to 0.040- or 0.060-inch oversize, we strongly suggest never going over 0.040-inch oversize due to the thin wall casting nature of small-block Fords. If there's core shift or you intend to run it hard, you'll be cruising on thin ice. If you must keep an existing block that is already 0.040-inch oversize, we suggest having the block sleeved, which on average costs $100 per cylinder, plus the cost of each sleeve.
This month, we're following along as Jim Grubbs disassembles this never-torn-down 289 High Performance and takes care of the machine work. Next month we'll tally materials and then assemble and dyno our Hi-Po engine.