You will find two crankcase alignment pins, one at the top, the other at the bottom. These pins must be removed before the crankcase can be split.
The pins are tapered, so proper procedures must be followed to avoid damaging the pins and crankcase. The narrow end of the pins face the cylinder head, the larger end of the pins face the intake manifold. These pins should have been removed prior to removing the crankcase bolts, so reinstall (just snug them up) the two upper and two lower crankcase bolts before driving the pins out. Using a small punch drive the pins out hitting them on the cylinder head side toward the intake manifold side of the crankcase/block.
Once the pins are out, remove the crankcase bolts, please recheck to make sure you have them ALL out. Now, using a large plastic or rubber hammer, tap the crankshaft toward the intake manifold side of the block. The crankcase should split apart easily, stop and recheck if it does not. Never pry or use a chisel to separate the crankcase halves.
Feel free to post pictures if you continue to have difficulties.
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