Tips for assembling a Buick 401 Nailhead V-8

The Redline Rebuild Buick Nailhead has finally reached the assembly phase and Davin has decided it is a great time to share a few tips on how to prepare a short block. From proper oil clearance measurement to making sure the valvetrain is serviceable after assembly, the details matter and Davin makes sure to get it right for this turquoise Buick.

The cylinder heads were prepped, leaving the bare block on a stand as the last bit that needed assembly attention. As the small parts move from a table into the block, Davin talks through small tips that ensure this engine will live a long and happy life.

For starters, the bearings and main caps get installed and torqued before the crankshaft is even in the same zip code. It is important, as the inside diameter of the bearings needs to be two thousandths of an inch larger than the outside diameter of the crankshaft. This minute amount of space allows for critical oil flow. If the crank and bearings were perfectly matched, there would be no space for oil, and if the clearance was too large, the oil would not provide the proper protection and the crankshaft could hammer the bearings due to low oil pressure. Either way, it would be a disaster.

The camshaft is inserted, and the pistons are up next. In the process of laying out the piston rings, Davin finds one that is obviously wrong with its gigantic end gap. Even the Redline Rebuild master is not immune to odd delays and setbacks. He also learned that, unlike so many other engines that share pistons rings with other engines, the 401 Nailhead is unique.

With all the proper rings installed correctly and the connecting rod bearing oil clearance checked, the pistons find their snug cast iron homes. Only then can the cylinder heads get installed and torqued down, allowing the cam to be degreed to the specs from the camshaft manufacturer.

The parts seem to speed off the table and onto the engine, with the final result ready for transplant from the engine stand to the run stand. With fuel, electrical, and cooling connections successfully completed, it’s time for Davin to press the starter button and break in the cam. You’ll have to stay tuned for that, since this update doesn’t include the sound of this Nailhead’s exhaust note.

If you want to be the first to hear it and see the artistry of the Redline Rebuild time-lapse, be sure to subscribe to the Hagerty YouTube channel to receive notifications when each new video goes live. It won’t be long now before this Buick is headed for a new home under a hood, but that is for another time.