What is a 350 Bored 60 Over?
The phrase "350 bored 60 over" refers to a specific engine modification, primarily used in the context of internal combustion engines, particularly V8s popular in the automotive world. Let's break down each part to understand its meaning:
350: This refers to the engine's original displacement, measured in cubic inches (ci). A 350ci engine is a common size, particularly associated with Chevrolet small-block V8s. This number represents the total volume of all the cylinders combined.
Bored: This term signifies that the engine's cylinders have been enlarged. The cylinder walls are machined to increase their diameter, thus increasing the overall volume of each cylinder. Boring increases the engine's displacement, leading to a higher power output.
60 Over: This indicates the extent of the cylinder boring. "60 over" means that the cylinder's diameter has been increased by 60 thousandths of an inch (0.060"). This is a common increment in engine machining.
How Does it Affect the Engine?
By boring the cylinders 60 over, the 350ci engine's displacement increases. This larger displacement allows the engine to ingest and burn more air and fuel, ultimately resulting in greater power and torque. However, it's crucial to understand that simply boring the cylinders isn't the only modification needed. Other components may require adjustments or replacements to properly support the increased power output, including:
- Pistons: New pistons with a larger diameter are necessary to fit the bored cylinders. These pistons are often custom-made or selected to match the specific bore size.
- Rings: New piston rings are required to maintain a proper seal in the enlarged cylinders.
- Connecting Rods: Depending on the extent of the bore, the connecting rods may also require modification or replacement.
- Crankshaft: The crankshaft might need balancing to accommodate the changes in mass and inertia caused by the larger pistons and other modifications.
What are the potential downsides?
While boring an engine increases power, it also has potential drawbacks:
- Cylinder Wall Thinning: Boring reduces the thickness of the cylinder walls, potentially weakening them and increasing the risk of damage or failure.
- Increased Wear: The larger cylinder diameter might increase piston ring wear if proper clearances aren't maintained.
- Cost: Boring an engine and installing new parts is a relatively expensive modification.
Frequently Asked Questions (Based on common online searches)
What are the common bore sizes for a 350 small block Chevy? While 60 over is common, other sizes are possible, depending on the engine block's condition and the desired power output. Smaller increments like 30 over or 40 over might be chosen to minimize cylinder wall thinning. Larger increases, beyond 60 over, are possible but risk significantly weakening the cylinders.
Can I bore a 350 block more than 60 over? Yes, but the more you bore, the thinner the cylinder walls become, greatly increasing the risk of damage. You would likely also need to replace parts like the block itself if it cannot handle the stress of further modifications.
How much horsepower will a 350 bored 60 over produce? This is highly variable and depends on many factors beyond just the bore size, including the camshaft, intake manifold, carburetor/fuel injection system, heads, and exhaust system. A properly built 350 bored 60 over can significantly increase horsepower, but an exact figure is difficult to pinpoint without knowing the specifics of the build.
In conclusion, "350 bored 60 over" describes a specific engine modification that increases power, but it's a complex process requiring careful planning and execution to ensure both performance gains and engine longevity. Professional expertise is strongly recommended when undertaking such modifications.
