The Buick straight-eight is looking good after its paint job last week, but that doesn’t mean the assembly process is running completely smoothly. Davin got all his ducks in a row before starting this project—just like he does each time—and the cylinder head still presented him with two problems which weren’t immediately solvable.

“There is always a chance for a situation like this, even when using all the “correct” original parts,” says Davin as he stares at a table holding a plethora of springs, shims, and valves. “The fact we are using a few non-original pieces only elevates the chance.”

The problems arise from the retro-fit valves Davin’s chosen for the Buick 400. The seat diameter is slightly larger, which makes for better airflow, but the stem is causing two issues. The first is a slight discrepancy in length, which Davin resolves with an extra shim under the valve spring. No big deal. The second problem with the stem, though, lies in a step machined just below the lip for the keeper. The step is in the perfect place to catch on the valve stem seal as the valve cycles through its travel.

In addition to troubleshooting the valves, Davin is also confronted with an interference fit between the inner valve spring and the cylinder head. The inside diameter of the spring is just a bit too small and gets hung up on the lower portion of the casting for the valve guide. Davin has a cutter that he thinks will solve the problem, but he hopes cutting a relief won’t cause more problems.

Such are the trials and tribulations of engine building. Problems and setbacks pop up, often at what seems the worst possible time. Davin and the team will need to do some research to build this Buick correctly, but the time investment is worth it for an engine we can trust and don’t have to rebuild after a few drives. Be sure to subscribe to the Hagerty YouTube channel to discover how Davin tackles the challenges the Buick straight-eight throws his way!