How to Build an SBC 327 CI Engine

by Moss Strohem

Chevrolet manufactured the 327 cubic inch, or "CI," V-8 engine from 1962 to 1969. It was used in standard-performance cars and trucks as well as in the high-performance Corvette. Based on the same block platform as all other first-generation small block engines, its displacement was achieved by expanding the cylinder bore to 4.00-inches and using a crankshaft stroke of 3.25-inches. It was the largest GM small block produced until 1967, when GM debuted the 350 CI engine. It was rated as high as 375 horsepower (1964 and 1965 Corvettes) and as low as 210hp (1968 and 1969). Small block parts interchangeability makes the 327 build very similar to all other SBC builds.

Engine Disassembly, Cleaning and Prep

Locate or purchase a core 327 CI engine. While they were popular engines and remained in use well into the 1980s, it is unlikely that many are available in salvage yards. An option is to use a widely-available 350 engine as a core for rebuilding, but a 1968/1969 327 or 1968 to 1973 307 large-journal crankshaft will be required. As an alternative to that, a new crankshaft can be purchased with the proper bearing journal sizes and 3.25-inch stroke for the 327 displacement from the 350 block, but different pistons for the shorter stroke will also be required.

Take the engine block and major components to an engine machine shop for cleaning and inspection. If undamaged and suitable for rebuilding, the block can be prepared for re-assembly. Machining services such as cylinder over-boring, main bearing saddle align-honing and cylinder block decking/squaring may need to be performed on the block. (If the cylinders require machining, the displacement will increase to as much as 337 CI, assuming a .060-inch increase in bore diameter.)

Instruct the machinist to inspect the cylinder heads, crankshaft, connecting rods and pistons. Have the heads reconditioned with a performance valve-job and replace any defective parts. The rotating assembly (crank, rods and pistons) need to meet exacting tolerances. Have the machinist inspect and recondition, as needed.

Upon completion of the machine work, clean all engine parts a final time with hot, soapy water and dry thoroughly. Spray or wipe all machined surfaces with oil or other rust-inhibiting solutions. Paint the exterior of the engine block and heads.

Order/source any additional parts, such as an overhaul kit (including rings, bearings, gaskets, etc.), new camshaft/lifters or other items to renew or increase performance.

Engine Assembly

Attach the engine to an engine stand and rotate it upside down. Install the main bearing inserts and coat with a generous amount of oil or assembly lube. Insert the upper front and rear main seals. Set the crankshaft into place carefully and install the main bearing caps. Torque the main cap bolts to the recommended value (foot-pounds). Rotate the engine so that one cylinder bank is vertical.

Install the piston rings on all pistons according the instructions in the assembly manual. Install the connecting rod inserts into the rods and rod caps and lubricate with oil or assembly lube. Using a ring compressor, carefully install the piston/rod assemblies into each bore making certain that the rod bolts do not mar the crankshaft bearing surfaces (use 2 to 3-inch pieces of 3/8-inch hose on the bolt threads). Tap the assembly into the bore, making certain not to force it into place. Attach the rod caps and loosely bolt them into place. Repeat for all cylinders, rotate the block to vertical for the opposite bank of cylinders and install the remaining four piston/rod assemblies. Rotate the engine to upside down and tighten all rod bolts to the proper torque values. Install the oil pump assembly.

Rotate the engine to right-side-up. Press the crankshaft timing sprocket onto the crankshaft. Install the camshaft and lifters, and install the timing chain and camshaft sprocket. The "short-block" engine is now assembled.

Lay each cylinder head gasket on the cylinder decks, coating them with adhesive/sealer as per the manufacturers instructions, and set the heads on the short-block and install the head bolts. Tighten to the recommended torque values in three graduated steps. Install the pushrods and tighten the rocker arms to hand-tight. Adjust the initial valve-lash according the the engine assembly manual. The engine "long-block" is now assembled.

Continue installing additional components -- harmonic balancer timing cover, water pump, intake manifold, etc. -- as per the assembly manual using the correct torque values on the bolts/fasteners. Be certain to double check all the completed tasks and make certain no loose parts or tools are left inside the engine before installing the oil pan and valve covers. The engine is ready for installation and initial run-in.

Warning

  • close The rod and main bearing journals on the 327 crankshaft increased from 2.3 to 2.45 inches in 1968. When interchanging crankshafts or ordering bearings, be certain to use the proper sizes.

Items you will need

About the Author

Moss Strohem has a background in business and finance, and an avid interest in youth sports, health, nutrition and physiology. He writes both technical information and market commentary as a private consultant and has researched and authored business plans.