383 Engine Build - Three Eighty Three: Some Machining Required

The honing process took just over 30 minutes. Preventing the mains from overheating and expanding is critical during the course of honing. Consolo checked with dial calipers to reveal two things: Our center cap looked good, but the rear cap was still too large. The cap was then removed, cut, and reinstalled. Additional passes of the hone revealed 2.6410 inches from the dial indicator. Some hones have a tendency to taper the mains, so flipping the block around eliminates the inconsistency in the machining process and will help keep things in line.

Removing the factory head dowels will help expedite the machining process. Our particular block needed to be decked to create a new surface. Using a special puller, we removed each dowel with care.

Taking full advantage of QMP's facilities, we opted to deck, bore, clearance, and chamfer our block in the fully automated CNC mill. We've learned that a limited number of machine shops have access to one. Automation's an added bonus as it eliminates any measuring errors that may occur with a manual decking, boring, or resurfacing machine. Another advantage is how quickly blocks can be machined and handed back to you for final assembly, which can be crucial for many builders.

Bore Sizes
Our factory bore sizes were less than ideal. Here, on the CNC's screen we could clearly see each cylinder's bore size. The largest bore before cutting was 4.0073 inches and our smallest came in at 4.0023 inches.

Taking over the reins on the CNC mill, Brad Lagman began to map out our assault on the block. After setting the cutting tool and with the touch of a button, Lagman ordered an immediate 0.030-inch be removed from each cylinder to a depth of 5.900 inches. Not only did the CNC bore each cylinder to precise specs, it also bored deep enough to clearance for the honing process. After boring, the CNC head moved over 0.0010-inch and dropped to a depth of 6.200 inches. From there, a step-notch is created in the bottom of each cylinder, allowing the bore-honing stones ample room to spin, once again eliminating bore taper and broken stones.

Decking the surface of the block was next. Visibly, a thick layer of rust had accumulated on the surface and had to be removed. During the automated probing of the surfaces, our lowest deck height came in at 9.0084 inches. Each pass on the CNC removed about 0.004 inch of material, until the surface was as smooth as glass. All in all, our factory block was milled to 9.007 inches.

A cutter was used to remove the top edge of its cylinder wall material. Separating QMP's technical level of machining from others, the company designed a chamfering program for the tops of each cylinder. Galling the piston skirts or snapping rings is no longer an issue.

Fruits Of The Labor
Our block was close to complete when it came out of the CNC machine. (A) Here, the clearancing of the bottom of each cylinder is evident. While this could take a full day of grinding, QMP's programming performed the same job in 4 minutes, 9 seconds. (B) Our cylinder walls were completely bored and perfect. (C) Note the bottom clearancing of the block to allow a full sweep of the bore honing stones.

Spending extra time to chase the head bolt threads is always a good idea. Here, we used a 7/16-inch thread tap to clean and debur the factory head boltholes, which ensures proper loading of the bolts.

QMP ditched the traditional style hone-torque plate for their custom designed torque plate, which mimics a small-block aluminum cylinder head, allowing them to emulate the load when honing the cylinder walls.

For the final step, QMP usually implements a four-step honing process that utilizes four different stones to achieve a smooth surface. The final step of honing uses a Delron shoe and micro brush to create a super-slick cylinder wall surface. From here, we'll give the block a well deserved wash and a fresh coat of paint.