Building an engine is a sort of rite of passage for motorheads, one that holds the power to provide a tremendous sense of accomplishment, though it can also bring the pain and frustration of failure. Last month, we detailed the first segment of the procedure, walking you through the core-selection process and the various machining steps to turn a worn-out chunk of iron into a fresh foundation for newfound power. By this point, a block has been found, stripped of its worn-out parts, cleansed to remove the years of gunk, and given a clean bill of health by the machine shop, verifying that there are no life-threatening fissures or wear beyond the limits of refurbishment. All critical surfaces should now be machined, including overbored cylinders, trued decks, resized connecting-rod bores, and honed main-journal saddles. Threaded holes should also by now be cleaned, and any damaged threads should have been chased, tapped, or coil-threaded-whichever is the simplest means of correction. In addition, all the required parts for reassembly should have been selected and procured.
Now it's time to start assembling the new engine. This portion of the build most easily allows the owner to become interactive, as the tools required are basic, save for some specialty items and measuring devices, which can, for the most part, be obtained at reasonable prices. But success here still requires more than basic wrench spinning; to get it right the first time and ensure that it stays together, you need to take it slowly and refer to expert sources for guidance, be they your machinist or a good manual or book. This time around, our expert assistance came from JMS Racing Engines in Monrovia, California, where Robert Hendrix oversaw the assembly of our small-block 400. Take a look at our engine coming together, and start planning yours.
Spin-balancing is often considered an optional step in engine rebuilding, mostly because a standard rebuild doesn't typically alter the internal weights of the rotating assembly too much, and even factory-assembled engines aren't right on the money. But for a performance engine that will see harder use and more trips to the upper end of the tach, a balance job is money well spent. If the engine in question has forged pistons in place of cast, nonstock rods, or particularly if the stroke has been altered, spin-balancing should be considered mandatory. Our 400 will use longer, aftermarket rods, so it needs a spin. It's also externally balanced, so the harmonic balancer and flexplate are attached for the process.
Once you're actually ready to begin assembly, the block should be completely clean. Most professional engine builders recommend washing the block with hot, soapy water to make sure any residue from the machining processes is removed. Metal shavings, grinding-stone grit, and blast-cabinet media can all hide in oil passages, only to come out later and wreck stuff. Invest in a set of engine brushes, and scrub every orifice.
Remember that a block that's been through the machine shop has almost certainly been stripped of all manner of plugs and caps, some of which you may not even be familiar with. Leaving even one out can mean a loss of oil pressure and possibly a big mess, one that may require serious disassembly to correct. Consult with a manual specific to your engine, and ask the machinist for guidance. This plug is inaccessible once the cylinder head is installed; use thread sealer to make sure it doesn't seep.
We had the oil-galley press-in plug bores tapped to accept screw-in plugs to resist leaking under high-winding, high-oil-pressure situations. The plugs should be coated with Teflon sealer. Freeze plugs should be treated to a thin coat of Gaskacinch or a similar product.