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20-Dec-99 Block Prep Part 3

Cylinder Honing

ImageBefore honing the block we will need to clearance it for longer rods. Because were building a 383 there's a longer stroke than a 350. A 350 has a 3.480” stroke and a 383 has a 3.750” stroke. Since the 383 has more swing in the crankshaft we need to clearance the block to allow room for the rod. We are using an H-beam rod that is a little stronger but also bigger than a normal rod we'll need to clearance a little more.
ImageBecause Sehr Performance has done so many 383 stroker motors they have a fixture they use to measure the clearance.
ImageAfter clearancing, the block is then put into a state-of-the-art CK-10 honing machine. Every race shop in the country probably has one of these. It ensures a perfect straight round bore. A straight round cylinder bore is very important and can make a difference of 30 to 40 horsepower!
ImageBefore honing a torque plate is bolted on to simulate the head. When a head is torqued down it can literally pull the cast iron around the cylinder walls, creating an imperfect circle. Without the torque plate the cylinder walls could end up being up to 2 or 3 thousandths off.
ImageThe cylinders are checked and rechecked throughout the honing process to assure that they are perfectly round and to specs (to .0001). The cylinders can heat up while honing so it's important to skip from cylinder to cylinder while honing. Three stones are used to progressively smooth the walls to their final shape.
ImageThe cylinder walls have a 30-degree crosshatch to allow the rings to seat correctly. Cylinder wall finish is very important. A perfectly smooth cylinder wall can produce more horsepower because of less friction but will not allow the rings to ever seat correctly. This is usually reserved for full out race engines. We are building a 100,000-mile motor however so that's why the swirl finish.