After the disassembly, cleaning, and inspection, Craig prepared to deck the engine block. This procedure is necessary because the cylinder-block deck surface sometimes develops irregularities that can cause compression and water leaks. The flatness of the block deck can be easily checked by using a straightedge and a feeler gauge. If the maximum deformation at any point is greater than 0.004 inch, the block needs resurfacing.
The term decking is used for the machine process that trues the head-gasket surface of the block. Most of the time, the objective of decking is to end up with a flat surface cut that is parallel with the centerline of the crankshaft and at the correct angle to the cylinder bores. Another use for this procedure when building a V-8 is to make sure the surface of each deck is the same distance from the crankshaft. Decking can also be used to increase the compression ratio by reducing the quench volume and bringing the piston closer to the top of the bore when at TDC. Our SD-455 block was decked 0.020.
When the crown of the piston is level with the deck, it is referred to as a "0-deck engine." A positive deck has the piston come slightly out of the bore when at TDC. Most Pontiac engines left the factory with a negative deck height. This means the piston crown never reached the top of the bore.
When metal is removed from the block or heads on a V-type engine, the heads will be positioned closer to the crankshaft. This will result in either machining the intake side of the cylinder head or the manifold itself for proper fitment.
Many Pontiac shops use stones...
Many Pontiac shops use stones to grind the necessary angles into the valve seats. The angles used for these heads are 30, 45, 60, 75, and 82 degrees for the intake and 30, 45, 55, and 82 degrees for the exhaust. RaceKrafters uses a special machine that cuts with a high-quality tool instead of grinding. This is the proper and modern procedure for the best performance. It creates much more accurate valve-seat angles than a stone. The procedure improves low-lift flow on both ports when the valve is just coming up off the seat.
With the ports roughed-in,...
With the ports roughed-in, the final surface is applied with a sandpaper roll to create a smooth texture. This is called polishing.
The new valves were cut to...
The new valves were cut to the proper angles on a Kwik-Way valve grinder. This step was executed by Bob using the many years of experience he has with cylinder heads.