The Best Upgrades to a Chevy 350by David Marsh
The Chevy small block engine has been around since Eisenhower was president. Chevrolet created a strong after-market for the engine by making so many of them and making them easy to work on. Performance enhancing changes are effective, but there is a warning. Any change to the engine may run into local ordinances concerning pollution or noise. Always check first. This article assumes that the engine is run on the street, not the track, and used for everyday driving. Gains in horsepower are dependent on the specific engine being modified and vary widely.
The System Approach
All changes to the engine should be coordinated to all other changes since the engine operates as a system, not a discrete set of parts. For example, a new set of headers won't help if the carburetor and manifold aren't swapped out as well. Do the research before you purchase your upgrades.
Inexpensive, Do-it-at-home Changes
Get headers. The easiest performance enhancer on the Chevy 350 is a new exhaust system because it's the weak point in the stock setup. The carburetor, manifold and valves are big enough to start with. The performance suffers because of the small exhaust setup. Adding headers simply brings that part of the system up to par with the rest of the parts. Chevy High Performance Magazine installed a set of Hooker headers onto a stock engine and saw an immediate increase of 16 horsepower and a more dramatic increase of 53 foot-pounds of torque. Headers bolt onto the block and attach to the stock exhaust pipes and catalytic converter. Headers cost under $200 and an afternoon in the garage.
Buy a new carburetor and intake manifold. The new headers allow for a bigger carburetor and manifold. If you push more fuel/air mixture into the engine, more horsepower comes out. After-market carburetors and manifolds offer bigger pathways for the fuel-air mixture with smoother surfaces and faster air flow. Horsepower increases for carburetor and manifold are dependent on the rest of the engine; however, gains from 20 to 50 horsepower and the same number in foot-pounds of torque is reasonable. The cost is less than $200 for the manifold and under $400 for a reconditioned carburetor.
Install a performance camshaft. Cams open and close the valves inside the combustion chamber. A cam which keeps the valves open longer means the combustion chamber can be filled and emptied better. Radical cams affect the engine at idle as well as the behavior of the engine in low speed situations. A better camshaft may add up to 20 horsepower and costs under $150.
Invest in a new cylinder head. The cylinder head is the piece of metal that sits above the combustion chamber. It holds the valves, valve springs and the intake and exhaust runners. A new cylinder head comes with bigger valves, intake and exhaust runners with smoother sides for better airflow. It should be matched to a new camshaft. This fix will immediately add 100 horsepower. The cost is typically under $200.
Computer chips can be changed in most cars. It isn't economical or convenient to change the chips that control the Chevy 350. Chevrolet began installing computer chips in non-removable cases in 1997. There are after market controllers that do the same thing but they're expensive and complicated.
Expensive, Get-some-help Changes
Get a super charger or turbocharger. Both push more air and fuel into the combustion chamber. With the proper setup, you can count on a 6 to 8 percent increase in horsepower per pound of boost. The average stock 350 with cast iron pistons can handle seven pounds per square inch, which results in about 50 percent more horsepower. You may want to invest in new forged pistons that can handle far greater pressure. A good blower, such as superchargers used on diesel engines, can give boosts of 40 to 50 pounds per square inch. Increasing your horsepower that much requires a new block and completely forged interior parts, but it means a potential horsepower increase of 400 percent.
Turbochargers use exhaust gas pressure to spin a turbine to draw outside air into the engine. However, a turbocharger lags behind the engine as it waits for exhaust pressure to build up. In larger turbochargers, the mass of the turbine becomes an issue and contributes to lag. Superchargers hook directly to the engine by a belt. There's no lag, but it takes a substantial amount of horsepower to move the supercharger. There is a drawback in both turbocharging and supercharging in that more air means more gas. The fuel economy suffers when the car is driven in a spirited manner. Superchargers are approximately $4,000, plus installation costs. Turbocharges are less than $1,500, plus installation costs.
Increase the bore and stroke. The width of the cylinder is the bore. A machinist can remove metal from the bore to increase the width of the combustion chamber so it can handle bigger pistons. New crankshafts and pistons increase the stroke, which is the measurement of the drop of the piston as it reaches the bottom of its stroke inside the cylinder. Stock engines are limited in bore enlargement because of the lower strength of cast iron and the thickness of the cylinder wall. After-market engines are stronger and have thicker cylinder walls. Increasing the bore and stroke can increase the size of the engine from 350 to 450 cubic inches or more. Bore and stroke enlargement is very dependent on the particular engine and the use the engine faces after the work is finished. It's also expensive. The cost and horsepower increase for a bore and stroke enhancement are dependent on the engine and the technician doing the work.
- dragster engine image by Robert Young from Fotolia.com