Little Big Chief - Part I: Basic Machining - Pontiac Tech

It's a good idea with any engine to check for cracks in the block before a major investment is made. This was especially critical with a near 40-year-old casting. Often called Magnaflux, which is actually a trade/brand name, a magnetic field is introduced and the part is sprayed with a special fluorescent solution. Next, the sprayed area is viewed with a black light. Any cracks will then be easily seen. The 350 checked out perfectly-no cracks were detected.

The cylinder heads can also be magnetically inspected, but to confirm the integrity of the water jackets, a pressure check is required using a special machine. Magnetic inspection will only detect external cracks. As with the engine block, the No. 17 cylinder heads were fracture free.

With the bores measured and found to be worn out of round and having a ridge, it was decided that a standard 0.030-inch overbore was required to true the cylinder walls and properly fit new pistons. The block was dial-indicated onto the boring bar in preparation for material removal. No torque plate was used because RaceKrafters didn't have one for the 350's bore, and making one for this project would've been cost prohibitive

Once the block was bored, it was mounted in a state-of-the-art Sunnen SV-10 computerized cylinder hone-used by many NASCAR and NHRA Pro Stock engine builders-for the final sizing and to produce the desired cylinder wall finish. This machine monitors the rotating torque and it can stop and dwell in one place to remove more material in tight areas as needed. It's the equivalent of a CNC hone. The cylinder hone procedure is one of the most important steps in Pontiac engine rebuilding because it determines the efficiency of the cylinder seal. The final finish was done with a No. 500 diamond stone.