Performance engines benefit from port-matching to smooth intake and exhaust flow.
The first and most important step in performance-engine building, beyond simple parts replacement, is to port and polish the heads. Although a full port job is something best left to shops that specialize in performance-head design, a simple port-matching and cleanup is well within the capabilities of the do-it-yourselfer, and can yield substantial increases in torque and horsepower. The perfect time to perform this task is while the head is off and disassembled for an engine rebuild.
Instructions
1. Bolt the intake manifold and exhaust header to the head. Spray ink into the intake manifold so that it will mark the overlapping area on the head. Be careful not to spray too heavily, which could cause runs.
2. Turn the head over and spray ink into the exhaust valve pockets to mark any overlapping sections of the header flange.
3. Remove the header and intake manifold. Be careful not to smudge the ink on the intake mounting surface.
4. Install a sanding drum in the die grinder and grind away any overlapping areas in the exhaust header ports. Gently smooth and round the transition into the ports. Be careful not to grind through the walls of the tubing.
5. Install a stone in the grinder and grind away the marked overlapping area in the intake ports of the head. Don't grind too deep; leave the last bit of material for the sanding drum.
6. Install a sanding drum in the grinder and finish matching the intake ports. Keep a straight angle into the port; do not allow any hollows to form.
7. Turn the head so that the combustion chambers face up. Install a round stone in the grinder and smooth the valve pockets without changing their basic shape. Grind down parting lines and casting flash, and make a smooth transition from the port passage to the valve seat. Be careful not to touch the valve seat or valve guide with the stone. Do not try to make a mirror finish; just eliminate the most obvious roughness.
8. Clean the ports, valve seats and guides with the brush, detergent and hot water. Allow to dry, and oil to prevent rusting.
