How to Put the Main Bearings in a 383 Stroker

The Chevrolet 383 cubic-inch stroker motor is a popular engine modification based on the Chevrolet 350 cubic-inch small-block V8 engine. A stroker motor is an engine that has had its crankshaft stroke altered by replacing the stock crankshaft and rods with a special stroker crankshaft and rods. An engine can be stroked to either increase or decrease its displacement. In the case of the 383 stroker, a crankshaft with the same stroke as the Chevy 400 small-block is used to increase the displacement to 383 cubic-inches. This is a very popular modification for the Chevy 350 engine.

Instructions

1

Spray a shop rag with parts cleaner and wipe each set of bearing halves. Do not mix up the bearing halves. There are five sets of bearings. Four are the same, with a solid bearing half and a bearing half with a groove and a hole in the center. The fifth one is the rear main bearing and has a large flange on each half. One half also has a groove and hole in the center. The halves with the grooves and holes fit into the engine block.

2

With the engine block inverted, spray a shop rag with parts cleaner and clean each main bearing saddle -- where the bearing half fits -- in the engine block. Clean the bearing caps the same way. The surface of the seats and caps must be clean and dry.

3

Seat a bearing half -- one with the groove and hole -- in the engine block. Note that the block has a small notch that matches up to the small tab in the end of the bearing half. Push the bearing half down until it is fully seated in the engine block. The hole in the center of the bearing should be matched up with the hole in the engine block. This is how the bearings are lubricated.

4

Seat the other bearing half in the main bearing cap. Match up the tab on the bearing with the notch in the bearing cap. Repeat this process for all of the other bearing sets. The rear main bearing fits the same way. The engine block and cap have grooves in them for the large flanges.

5

Spray a shop rag with parts cleaner and clean the main bearing journals on the crankshaft. You will be test fitting the crankshaft and checking the oil clearance so everything must be clean and dry.

6

Carefully lower the crankshaft into the engine block. Place a small piece of green Plastigauge that has a measurement range of .001- to .003-inches across each main bearing journal on the crankshaft. The Plastigauge should be pointing front to rear, not side to side. Plastigauge looks like a thin string. Mount the bearing caps over the crankshaft, onto the engine block. Install the main cap bolts and use a torque wrench to torque them to the recommended value. Do not turn the crankshaft during this procedure.

7

Use a ratchet and socket to loosen and remove the cap bolts. Remove the bearing caps. Note that the Plastigauge has been smashed flat. Measure the Plastigauge by comparing the width of the Plastigauge with the measurement chart on the side of the Plastigauge wrapper. Insure that the reading you obtain is within the main bearing oil clearance specification.

8

Remove the Plastigauge from the crankshaft by wiping it with a shop rag. Remove the crankshaft and wipe the bearing surfaces to remove any Plastigauge. If you get a measurement that is incorrect -- either too small, or too large -- you will have to consult with a machinist or the store where you got the stroker kit from.

9

Coat the surface of each bearing half with a small amount of moly-type assembly lube to protect the bearings and crankshaft on initial startup. Mount the bearing caps onto the engine block with the caps facing the right way. They have an arrow on each cap that points forward. Also, be sure to return the first four caps to their original positions. Do not mix them up.

10

Replace the crankshaft in the engine block. Install the bearing caps and bolts. Use the torque wrench to torque the bolts to the proper specification. The crankshaft should turn freely in the engine block.