The Buick 401 Nailhead is making progress, but with each step the V-8 continues to create more work for Davin. Our last update showed that even in the early phases of disassembly, this grimy mess of an engine was not going to be an easy project. The continued disassembly proves it.

Even just parting the front accessory drive requires the use of hammers and patience, but the real story is hidden in and under the cylinder heads.

“The valvetrain looked pretty good considering the oil looked like it had turned to paste in the engine,” Davin says. “The shaft mounted rockers and near horizontal pushrods are a wild layout compared to a regular small-block Chevy or Ford.”

It is not just the appearance of the shaft rockers that makes them unique. The Nailhead gets its nickname from the near vertical positioning and relatively small size of the valves. With 401 cubic-inches to feed, Buick compensated for the awkward layout and small valves, which restrict flow, by giving the camshaft a profile with more lift to allow the engine to get enough air and fuel.

All that is glazing over the real development in this update—the cylinder heads come off and, boy, is it a horror story underneath.

Davin had been trying to free up the pistons in their bores for weeks, filling the cylinders with various penetrating oils and even milkstone remover, which he uses for cleaning and stripping rust from well-worn parts. In this case it doesn’t seem to have made much of a difference. The engine remains locked solid, which means the next episode is likely to bring out the heavy tools.

Be sure to stay up to date on the latest developments with this engine and Davin’s other projects by subscribing to the Hagerty YouTube channel to receive a notification when each update goes live. You don’t want to miss a rust-breaking episode.