Porting and polishing
Larger ports flow more fuel/air at higher RPMs but sacrifice torque at lower RPMs due to lower fuel/air velocity.Porting - maybe worth it, depending on what you want. It's easy to make things worse though. Polishing the inner surface of the combustion chamber in the head - maybe some benefit by reducing heat transfer into the head.
What is a Port/Polish Job? Port/polish work is a relatively simple process that is performed on the engine's cylinder head. First, the intake and/or exhaust inlets (ports) on the cylinder head are enlarged using a grinding or cutting tool.
Pocket porting refers to cleaning up the port runner area approximately one-inch before the intake or exhaust valve seat. Carefully opening that area closer to the valve seat diameter can wake-up many heads from 15- to 35-overall horsepower.
Cam and heads can gain you 100+hp. One of the automotive performance magazines ran individual tests regarding the performance differences between a set of aftermarket iron heads and aftermarket aluminum heads.
Aluminum heads dissipate (get rid of) heat much faster than iron heads. Aluminum heads will not automatically create more power than iron heads unless they flow more air and are installed on a higher compression ratio engine.
In general, head porting does not affect compression. Porting the head usually means enlarging the intake and exhaust runners, that's it. However, some porters "work" the combustion chamber, removing material for whatever reason. This will lower the compression.
The cylinder head is where a great deal of the action for running your engine happens. It contains the combustion chambers where the quick burn of fuel and air that moves the pistons occurs. The intake manifold feeds air into the head through the intake ports, past the intake valves and into the combustion chamber.
The more cubic inches the engine has, the more airflow the heads have to deliver. A head with 180 or 185cc intake runners will work well on a typical 350 Chevy street engine that makes 400 to 450 horsepower.
Even so, lighter is usually considered better for performance. Aluminum heads are easier to machine than cast iron because the metal is softer, and the heads are easier to repair because aluminum can be TIG welded to fix cracks and other damage. Aluminum conducts heat faster than cast iron.
Peak Torque and Horsepower
| Cylinder Head | Peak Horsepower | Peak Torque |
|---|
| Edelbrock | 395 at 5,900 rpm | 409 at 4,200 rpm (5) |
| Speedway | 381 at 5,400 rpm | 409 at 4,200 rpm (5) |
| Vortec | 378 at 5,300 rpm | 408 at 4,300 rpm (7) |
| Stock Iron | 358 at 5,800 rpm | 379 at 4,300 rpm (8) |
The Blocks for Chevy Heads Reviews & Buyer's Guide:
- Flotek 102505 Aluminum Cylinder Head for Small Block Chevy.
- GM Parts 12558060 Cylinder Head for Small Block Chevy.
- Dart 127121 SHP Cylinder Head for Small Block Chevy.
- Edelbrock 5073 Cylinder Head.
- Speedmaster PCE281. 2010 Chevy SBC 350.
Port and polish doesn't really ADD horsepower. Cams, pistons, turbos, nitrous, etc. add horsepower.
Upgrading your intake will not only increase horsepower, it can also change the rpm range at which the most horsepower is created.
The argument is that it works on golf balls because it creates a boundary layer of air and helps it move the ball faster and farther. So the dimples would (in theory) help create this boundary layer of air that would keep the fuel off the wall and in suspense and atomized.
Port Tools. All Port Tools are ground between centers to ensure absolute concentricity. They are made from heat-treated alloy steel with brazed carbide inserts. They are designed to enlarge a pre-drilled hole and easily produce a complex form. Port Tools can be used for both lathe and mill applications.
What is a Port/Polish Job? Port/polish work is a relatively simple process that is performed on the engine's cylinder head. First, the intake and/or exhaust inlets (ports) on the cylinder head are enlarged using a grinding or cutting tool.
When you dimple the port, you slow the air down wherever you put the dimples. The dimples do help prevent the flow separating as it passes the valve and valve guide, but the increase in skin friction due to the dimples means the mass flow rate is still lower.
New Member. porting refers to the fact that you are widening, polishing, or adding ports to a part of a saw, or a saw.
Once you have the intake off, you need to port-match the intake ports on the cylinder head. Don't even consider porting the intake until you've port-matched the heads. It's OK -- even desirable -- to have a manifold port that's slightly smaller than the head port, but you never want it the other way around.
The basic principle behind modifying a car is to have more air/fuel enter the combustion chamber. The port and polish basically makes it easier for air/fuel to flow into the combustion chamber and gasket matching permits a greater volume. (
Due to these differences in pressure difference during intake and exhaust, it is tougher to induct the air than to exhaust the burnt gases. Hence the intake valve has to be bigger than the exhaust valve.
Porting cylinder heads generally refers to the process of enlarging the intake and exhaust ports of an engines cylinder heads. Porting is usually done to increase airflow and horsepower at high RPM. Heads with smaller ports – un-ported – usually provide better low-end torque than ported heads.
