| Porting and Polishing Chevy Muscle Car Heads | | | | The entire port should feature a continuous |
| The heart of your engine is the cylinder heads. A | | | | smooth radius. The valve guide bosses can also |
| time-honored method for increasing Chevy | | | | be cleaned up but be sure to leave .125 of |
| muscle car horsepower and torque has been | | | | material surrounding the valve guide hole. You can |
| improving the air flow potential of the engine | | | | use abrasive rolls to polish the exhaust ports but |
| cylinder heads. There are many ways to do this; | | | | do not polish the intake ports. With the intakes, |
| expensive "bolt-ons" such as aftermarket heads, | | | | too smooth and you lose the turbulence needed |
| supercharging or turbo charging. For the real | | | | to thoroughly mix the gas and air being pulled into |
| gear-head with little money and basic mechanical | | | | the combustion chamber. |
| skills, porting and polishing the OEM heads is | | | | 2. Unshroud the valves by gently removing |
| always an option. | | | | material from the sides of the combustion |
| With just a few key modifications, most heads | | | | chambers. Match the head gasket with the bolt |
| can be made to flow 5 to 10% better than stock | | | | and dowel-pin holes in the head and then scribe a |
| and the effort only requires a few basic tools, | | | | cylinder-bore line around the chambers. Using |
| patience and a weekend's worth of sweat labor. | | | | machinist bluing or a dark felt tip marker will make |
| That's free horsepower! If you are doing a valve | | | | the scribe line easy to see. You then know how |
| job anyway, especially if upgrading to larger | | | | far you can safely grind but do not go outside the |
| valves, this improvement could be in the 20 to | | | | scribe line or serious sealing problems may result. |
| 25% range. | | | | Again, remove minimal material to avoid reducing |
| The Basic Steps Are: | | | | the compression ratio. Use some old valves in the |
| 1. Remove ridges from the intake and exhaust | | | | chamber to protect the seats while grinding. You |
| port bowls; this is formed when the valve seats | | | | can also polish the chambers with abrasive rolls; it |
| are cut and once the heads are disassembled you | | | | will reduce the tendency for carbon buildup. |
| can easily feel it with your finger; it's in the head | | | | 3. Port match the intake runners to the intake |
| just below the seat. Blend the ridge into the port | | | | using the intake gasket as a template for a scribe |
| walls using a carbide burr with a ¼ inch die | | | | line. Some say this is worth 4% more CFM, 2% is |
| grinder. A variable speed grinder and a light touch | | | | more likely, but every little bit helps. Do not polish |
| are best. Be very careful that the shank of the | | | | the intake runners or fuel puddling and loss of |
| burr does not come in contact with the valve | | | | flow turbulence could result - leave them a little |
| seat. Remove as little material as possible. | | | | rough. |