305 Chevy Engine: Ultimate Performance Upgrade

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Designed in an age of rising fuel costs, oil embargos, and stricter governmental regulations, the 5.0L V8 gets a bum rap, but it can be upgraded into a beast.

The 5.0L 305 Chevy engine is a small block produced from 1976 - 2003 for various F-body pony cars, light trucks, vans, and commercial vehicles. The 305 was used as the “Economy V8” to meet better fuel economy and emission standards. Despite low power numbers, there are ways to upgrade the 305 V8.

More often than not, the Chevy small blocks that get the glory and attention are high-performance engines that produce excessive power and roar like a caged tiger. But what happens if your remodel project doesn’t have any of those special beasts? What if, by chance, your rebuild involves the lowly 305 cubic inch motor that produced a measly 110 hp? Chances are you’ll consider swapping that turtle for something much quicker, but before you do, consider this: upgrading that 305 might be easier than you think. This article will examine some of the performance enhancements commonly done in the 5.0L engine, and often they can turn your engine from a mundane fuel miser to the monster you always dreamed of driving.

Table of Contents


The History Of The 5.0L Chevy Engine

The mid-70s was a tumultuous time for the auto industry, as rising fuel prices, an oil embargo, and stricter governmental regulations tightened Americans' confidence and wallets. The Big Three was forced to rethink their large V8s and begin producing more fuel-efficient engines to power the next generation of vehicles.

Chevy’s answer to the dilemma was to produce the 5.0L (305 ci) small block V8 as a cost-effective, “economy V8” to save money for customers at the pump. The engine was based on the 5.7L 350 V8, which shared several components. The new motor had bore and stroke dimensions of 3.736 x 3.48, producing 110 hp. Although the power output was somewhat pedestrian when muscle cars were still in people’s minds, most Americans understood the realities of the new world order where gas mileage and fuel savings took precedence over speed.

During the 1980s, the 305 and its variants rose to prominence and found their way into almost every vehicle GM produced. In some models, it was the only V8 engine offered. One important fact to note is that the 305 V8 (and its cousin, the 350) forced many of GM’s divisions to stop manufacturing their own V8 engines and use the 305 as a universal engine that could work for almost any GM family vehicle. This movement alone helped save production costs as all the car companies began to look for ways to streamline the process they used to build a car.

Several 305 V8s made their way into cars like the Caprice, El Camino, Camaro Z28, Iroc-Z, Monte Carlo SS, and the Pontiac Firebird TransAm (as optional engine choices). The L69 variant was one of the strongest 305 engines, producing 190 hp and 240 lb-ft of torque. While the powerplant offered in the Monte Carlo SS was slightly less powerful (180 hp), it was still plenty fast for its day. A Chevy sales brochure from 1985 told customers that the SS was powered by the “famous 5.0L V8” and that though they could tell more, they preferred to “let the Monte Carlo do the talking because actions speak louder than words.”

During its production run, many variants of the 305 would find their way into various vehicles, from trucks to vans. GM continued to improve the engine with new throttle body injection systems, hydraulic lifters, fuel rails, and more. The Vortec 5000 L30 was a truck V8 placed in 1996-2003 CK pickup truck and full-sized vans. The 305 V8 ceased as an engine option for production vehicles in 2003.

What Are Some Basic Upgrades That Can Have Big Results?

Over the years since its production, the 305 has gotten a bad reputation for being a Chevrolet small block motor without much power. Many classic car owners have opted to slap a 350 V8 (or other larger engines) into their builds, given the availability of these engines in junkyards nationwide. (The mass quantity of aftermarket parts means prices for a 350 ci engine are often lower than for the 305, so you can see why most auto experts recommend swapping out).

Why doesn’t the 305 get more love? Part of the reason the 305 is the rebuilders stepchild has to do with the small dimensions of the motor. Even though the 305 was built with various displacements, it was manufactured with a very small bore and stroke. (Chevy made the 267 V8 with the smallest bore size of 3.5 inches in the late 70s, and the 262 V8 was also in use with a 3.671 bore until they both were superseded by the 305).

The 3.736 x 3.48 bore and stroke dimensions can make finding some crucial parts, like, cylinder heads, pistons, and the like, difficult. Many aftermarket suppliers were well stocked with components for the 350 or 302 but failed to see a market for producing other items because the sales weren’t there. (If you look hard enough, some parts dealers, like Speedway Motors, stock plenty of 305 parts.

While the 305 might be the most misunderstood V8 engine in Chevy’s small block family, it doesn’t mean some improvements can’t be made to the “Economy V8” to improve performance and power.

Change The Carburetion

Many early 305s (before fuel injection) came with wimpy 2bbl carbs that limited air and fuel to be drawn into the chambers. There are a variety of intakes and manifolds that can increase power. Summit Racing has various intake manifolds and Edelbrock and Holley carbs. One of the most popular double pumpers for the 305 is the Holley 0-76750BL 750 CFM Ultra Double Pumper Carburetor.

Chevy started using TPI systems in 1985, and many aftermarket purveyors make throttle body fuel injection systems that can bolt on in place of a regular carburetor. With ECU fine-tuning and new EFI systems, a significant boost in horsepower and torque can be achieved.

Revamp the Exhaust

Many 305s produced in the 80s came with single exhaust systems that couldn’t cut the mustard. Replacing the old, worn-out exhaust with a new system that includes a new catalytic converter, high-flow mufflers, and headers can make a difference. The advantage of new exhaust is that these items often weigh less, provide better airflow, and look ten times better when installed. (Remember that every pound your car sheds will help it click a few tenths of a second off its track time).

Consider A Camshaft or Cylinder Head Upgrade

While increased horsepower numbers are great, the real power numbers come from the torque an engine produces. You need torque if you plan to challenge your buddy’s small-block Ford to a race. Many companies now produce inexpensive heads for the 305 that can easily be bolted in. (Remember that most new versions have torque-to-yield bolts that need to be replaced each time the head is removed, so do yourself a favor and don’t reuse the old bolts).

Replace Torque Converter

If your 305 has an automatic transmission backing up the engine, replacing the torque converter can boost power. You need to match the right transmission of your rebuild because GM used several different transmissions depending on the year and the model. (We also recommend getting a complete torque kit (Pro Pack) to have fresh gaskets, bolts, and other items you might need for the installation).

Consider Additional Boost

If you are a speed demon and need to add things like nitrous oxide, go for it. However, remember that the 305 engine is a small powerplant that can’t take too much boost without crapping out. (Most forums recommend a 100 shot of nitrous). While nitrous might be a tad risky (many engines have caught fire due to a nitrous oxide leak igniting), it can deliver some much-needed pep to this small block.

If you prefer a less dangerous solution, consider adding a turbocharger to the top of the engine. While the kit can be expensive ($3500 or more), the results are impressive.

What’s The Most Horsepower A 305 Chevy Engine Will Handle?

The maximum horsepower on an early 305 with natural carburation is about 400 hp. (Although some folks will push that number). A fuel-injected version of the 5.0L engine can bump up 100 hp relatively easily with minimal fuss.