The Chevrolet small-block V8 engine reigns as iconic in the automotive industry. The two most popular engines in the small-block Chevy are the 305 and 350. These motors are so popular that you’ll find variations of the original engines even in newer GM vehicles.
For the hot rod looking for the best engine to rebuild, you may be going back and forth between Chevy 350 vs. 305, wondering which is better. As far as dimensions are concerned, you wouldn’t be able to tell the difference between the 305 and 350. However, a closer looker at the bore size reveals that the 350 has bores that are ¼-inch larger than the 305.
Except for the bore, let us go deeper and find out what sets each of these engines apart.
Chevy 350 Vs. 305: Detailed Comparison
Generations, Models, and Years
The world’s first Chevy 350 engine came in the 1967 Camaro. Based on the 327, this engine was not about to take a back seat as it took over passenger cars and trucks in just about every level of tuning.
The first Chevy 350 version came in the L48 and was used in the Nova, El Camino, Camaro, and Impala. GM also used it in the 1969 – 1974 Holden Manaro and 1971 – 1974 Statesman. This version boasted a horsepower of 295 and 380 lb.-ft of torque.
The L46 was its second version debuting in 1969. This engine was optional in the Corvette with 350hp base gross power, and it helped Chevy stay in the game by crossing the 300hp mark.
Three more versions could surpass 300hp, and that’s the 1969 – 1974 ZQ3, the 1970 – 1972 LT1, and the 1987 – 2005 L31. The ZQ3 is revered for its high compression ratio of 10.25:1, a 780 CFM Holley 4bbl carburetor, and high-po camshaft.
Engines that reached 250hp were the 1973 – 1980 L82 and the 1985 – 1992 L98. All other engines from the 1970 – 1976 L65 to 1987 – 1996 L05 were under 205hp.
This 5.0L small-block premiered as the LG3 in 1976. It started at an underwhelming horsepower of 130hp since GM made it during the gas crisis of the 1970s. The brand made only eight versions of this engine, with the most powerful being its last version, the L30, in 1988. This motor could produce 230hp; hence it never came close to the 350’s power.
Chevy 305 versions include:
- 1980 – 1987 LG4 (170hp),
- 1982 – 1984 LU5 (175hp),
- 1983 – 1986 L69 (190hp),
- 1981 – 1986 LE9 (165hp),
- 1985 – 1992 LB9 (230hp), and the
- 1987 – 1995 L03 (170hP).
Displacement, Bores, and Strokes
The Chevy 350 is a 5.7L engine, while the Chevy 305 has a displacement of 5.0L. While it seems like a nifty difference, the 350 has a 4-inch cylinder bore compared to the 305’s 3.76-inch bore.
Although they share the same stroke size of 3.48 inches, the cranks are not interchangeable since the 350 has larger and heavier pistons making the counterweights on a 350 crankshaft heavier.
Still, the long strokes on the 305 help it make tremendous torque at low speeds, but it can’t tow heavy loads since its 3.76-inch bore limits it.
The small bores tend to restrict air to a great extent such that it’s impossible for 305 to run a 2.02-inch intake valve to amp the horsepower. Hence, if you were to try this type of modification, the intake valve could crash into the bore.
The 350, on the other hand, achieves its high displacement owing to its larger compression chamber and pistons with a 1.46-inch compression height.
But both have the same connection rods at 5.7 inches with construction from forged steel. In addition, they have the camshaft sitting directly above the crankshaft, owing to the overhead valve design.
Another feature that brings a difference in the displacement is the intake valves. On the 350, you have 1.94-inch intake valves, while the 305 bears 1.84-inch valves. Nonetheless, they have similar size exhaust valves at 1.5 inches.
Note that if you’re thinking of rebuilding the 305 with a larger 1.94-inch intake, you will have to take a step back since the bigger intake restricts airflow and hurts the horsepower.
Chevy 350 SBC started with an average compression ratio of 9.5:1 in the L48, but GM upped this number to 11.0:1 in the L46. This model and the ZQ3 that came in with a 10.25 compression had the highest number, yielding better efficiency. In addition, they could get more work done even with the same amount of fuel as in the other models.
The base version of a Chevy 305 has a compression ratio of 8.5:1 on its two-barrel carburetor. Later engines had a 4-barrel carburetor, but they maintained this compression ratio until the L69, which received a bump to 9.5:1. However, the L30 dropped its compression ratio to 9.1:1.
The 350 SBC sees better thermal efficiency between the two engines due to its high compression. Nonetheless, it will perform better with premium fuel, but the 305 will run without the risk of knocking when you use regular fuel.
The horsepower on both engines varies with the motor’s model year. Chevy 350 started with a meager 295 hp on the 1967 L48 model. However, its variants ramped it up to 350 by 1980 due to modernized induction systems and improved cylinder heads.
Looking at the 305, its lighter crankshaft and prop shaft can produce 230hp max at 4,000 RPM. When the engine is neutral, its output is 650 RPM. Meanwhile, this engine reaches a max RPM range of 4,400 to 4,800 RPM. This was in the 1980s when the engine received a hydraulic roller cam.
The typical Chevy 350 can output a maximum of 380 lb.-ft of torque. Coupled with its high displacement and horsepower, the 350 SBC makes a better engine for towing. However, you may find that fuel economy is low when hauling, so it’s best to look at the engine’s specific compression ratio and use high-octane fuel where possible.
Meanwhile, the Chevy 305 SBC started with 250 lb.-ft of torque in the LG3. It has been so except for L69, which could output 240 lb.-ft of torque. Nonetheless, the engine in the Camaro Z28 had an automatic transmission that matched its 275 lb.-ft of torque.
Again, the 350 SBC higher torque enables energy-saving and efficient driving. The engine also accelerates much faster than the 305 SBC.
Initially, the Chevy 305 had a carbureted fuel system in its early models until the late 1980s. These motors would struggle to change the fuel temperature and air pressure and could not measure the air-fuel ratio accurately. In the late 1980s, Chevy introduced models with Tuned Port Injection (TPI) system.
Similarly, early 350 models had carbureted fuel systems until the L89 used a TPI system.
By today’s standards, the Chevy 350 and 305 engines are considered low compression engines. However, any engine with a compression ratio above 9.5 like the L48, L46, ZQ3, L98, LU5, L69, LE9, LB9, and L03 should use 89 Octane and higher. The other models with compression below 9.5 can use 87 Octane with no problems.
If you can’t tell your engine’s compression ratio, try running lower Octane fuel and listen for pings. This is called detonation which means the fuel is exploding in the cylinder rather than combusting.
Test your engine under acceleration when climbing a hill or pulling a load. If you hear pings, it’s best to switch to higher Octane fuel to avoid engine damage.
Both 350 and 305 engines up to 1996 have a traditional wet sump oil system. They feature a block-mounted oil pump that sits on the rear cap, which is driven by a shaft. This shaft draws the oil from the oil pan using a tubular pickup.
The camshaft drives the pump at reasonable speeds to provide adequate oil flow. This is because the pump turns at half the engine’s speed. In this case, the top of the engine is the first to get lubricated, then the camshaft and crankshaft. This system is ideal for street rods and mild builds.
Models made after 1996 have a dry-sump system that utilizes an external oil reservoir in addition to the base sump. They can also have multiple oil pumps. This system can be found in modified racing engines since it prevents engine oil starvation. The oil temperature is also perfectly controlled, and the vehicle handles better.
The cost of rebuilding a Chevy 305 is similar to that of a 350. It will cost you anywhere from $2,500 to $4,000 for parts and labor.
On the other hand, buying either used engine is pretty cheap since you can snag them for under $200 from a junkyard and up to $1,000 for a good running 350 or 305.
Chevy 350 Vs. 305: Key Differences
Apart from the block’s casting numbers, the bore size is the primary difference between the Chevy 350 and Chevy 305.
Again, the 350 has a 4-inch bore, while the 305 comes with a 3.76-inch bore. This distinction goes to further warrant heavier weighted cranks on the 350.
Still, the smaller bore calls for smaller intake valves coming in at 1.84 inches to prevent extending over the bore.
In addition, the heads on a 305 are meant to fit in the small combustion chamber. As such, you cannot use 350 heads since they are for its 76cc combustion chamber as opposed to the 53cc chamber on the 305 SBC motor.
Chevy 350 Vs. 305: Interchangeability
The 350 and 305 Chevy engines have many similarities, so most of their parts are interchangeable. The external components, including the exhaust and intakes, bolt right into each motor. Nonetheless, since the 305 engine has a smaller bore, running 350 intakes will severely limit airflow.
The small ports on the 305 motor make its heads perform dismally on a 350. Again, it will increase the compression ratio to 12.1, so it will need premium fuel exquisitely.
But like I’ve mentioned, most parts interchange except for the pistons and rings. Nevertheless, it does not mean that interchanging the components will improve the performance of either engine.
What Year Is the Best Chevy 350 Engine?
The Chevy 350 has seen quite a lot of variations throughout the years. Yet, only some left a lasting mark on their users. These are the LT-1, L98, and the L31.
The LT-1 was a racing-inspired engine known for its high-performance parts. This motor featured a high-lift camshaft, solid valve lifters, and a 780 CFM carburetor with an aluminum intake.
1970 LT-1 could produce 370 hp at 6,000 RPM and up to 380 lb.-ft of torque at 4,000 RPM. This power allowed the Corvette to go from 0 to 60 mph in only 6 seconds.
The 1992 version of the L98 is a remarkable and memorable model due to its Tuned Port Fuel system, making the 350 retain interest.
The engine reigned for seven years as it could reach 230hp and could max out its torque and power without going over set emission standards.
This engine remains quite reliable despite its age. It does not require modifications for the street driver, and sellers offer a 100,00- mile guarantee.
It has a 9.4:1 compression ratio and can reach 255 hp at 4,600 RPM. Its torque rating is 350 lb.-ft of torque.
Read more: What Year Is The Best Chevy 350 Engine?
What Year Is the Best Chevy 305 Engine?
Again, 305 SBC engines vary widely. If you’re looking for a carbureted 305, you will find models like the LG3, LG4, and LU5 ideal.
However, the modern versions of the 305 have a fuel-injected system. Hence, models in the late 1980s to early 1990s are your best bet. The best years of Chevy 305 include the LB9, L03, and L30.
The carbureted models make significant street engines, including the LG4, while the fuel injection models are great for racing applications.
What Are the Problems of the 350 and 305 Engines?
A common problem of the 350 SBC is overheating if you use a radiator that does not match it. Secondly, the automatic choke tends to close in frigid weather, so it needs checks now and then to ensure that the choke plate is swiveling to open and close. In any case, the choke needs to always be open by 1/8 of an inch.
Since 350 engines have been around for decades, having them sit on the shelf waiting for a rebuild causes them to develop a clicking or knocking sound. This problem is usually caused by low oil pressure or restricted oil galleys.
Some noises on the 350 are perfectly okay to ignore, such as tapping noise from the camshaft. This noise is on 350 engines that reach 355hp and are equipped with aluminum heads.
Common Problems of the 305 SBC
The major concern about the 305 SBC for builders is its displacement. Since you won’t be getting much in the way of a power increase, swapping out the parts of the 305 seems like a waste of money compared to rebuilding the 350 for more power.
305 SBC bore size limits head flow since it necessitates small valves if you’re going for better airflow. It would perform okay for a street engine but not so much as a drag race motor.
Still, among the different versions of the 305 engines, you’ll find a considerable difference in horsepower between the carbureted and the Tuned Port Injection (TPI) engines. To this end, the TPI models had extra-long intake runners bringing about a difference of about 60hp between the two engine types.
Which Is Better: 350 or 305?
If you’re interested in an outstanding engine with excellent value, I’ll give it to the Chevy 350 engine. Firstly, it is a reliable engine that gives you superior performance for your money. Secondly, many 350 variants produce more than 300 hp, so many hot rodders will find it appealing.
While the 305 does better at fuel mileage because of its smaller displacement, ports, and valves, the 350 is excellent at power. All thanks to its larger ports, valves, and displacement. So, even if you’re getting better fuel efficiency with a 305, it does not make up for its deficiency.
350 SBC parts are easy to find, and you can swap out the parts with many small block engines to achieve the best application from this motor.
Hence, it combines performance, reliability, durability, and ease of maintenance in one powerful machine.
Best 350 and 305 Engine Rebuild Kit Recommendation
Best Chevy 350 Engine Rebuild Kit
Best Engine Rebuild Kits For Chevy 305
Understanding the differences and similarities between the Chevy 350 vs. 305 will go a long way in your new rebuild. To this end, the Chevy 350 is a great engine for anyone looking for lots of power and torque.
However, if you want a better fuel economy, the Chevy 305 is a better choice.
In addition, the 350 is preferable to customize for more power owing to its larger bore, which does not restrict airflow. Further, it has lots of aftermarket parts due to its popularity.
Now, you’re in the know!
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