Mercedes Mullins
The viability of a 5/16 fuel line supporting 330hp depends on several factors, including the type of pump, fuel, number of g-forces pulled in a straight line, and the presence of sharp bends or restrictions in the line. For a carbureted engine, a 5/16 line may be sufficient for up to 500 hp, while for an EFI engine, a larger line or a more powerful pump may be necessary to prevent fuel starvation. Some car enthusiasts suggest that a 3/8 line is a more suitable option to ensure adequate fuel delivery to the engine.
| Characteristics | Values |
|---|---|
| Fuel line support | 330hp |
| Fuel line diameter | 5/16" |
| Fuel type | Carb or EFI |
| Pump type | Mechanical or electric |
| Pump gas | Yes or No |
| Number of g-forces | N/A |
| Sharp bends or restrictions | N/A |
| Injector sizing | 30lb, 42lb, or Siemens Deka 60lb |
| Fuel pump capacity | 170lph, 190lph, 255lph, or 405lph |
| Fuel pressure | 0-40 PSI |
| Injector duty cycle | 80% or 84% |
| Fuel volume | N/A |
| Fuel bowl | Yes or No |
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What You'll Learn
A 5/16 fuel line will support up to 500 HP for a carbed SBC
The suitability of a 5/16 fuel line depends on several factors, including the type of pump, type of fuel, number of g forces pulled in a straight line, and the number of sharp bends or other restrictions in the line.
For a carbed SBC, a 5/16 fuel line will support up to 500 HP. This is because the lower pressure of a carbed engine compared to an EFI means that a larger line is required to achieve the same volume per minute. Therefore, a 5/16 fuel line will be sufficient for a carbed SBC up to 500 HP, as the system will not be taxed enough to starve the motor of fuel.
However, it is important to note that if the same car is fitted with EFI, a 5/16 fuel line may not be adequate on a race track. This is because EFI systems do not have fuel bowls, so there is no safety net if the pump cannot move enough volume to keep the motor fuelled.
Additionally, a mechanical pump and modern pump gas may cause issues with a 5/16 fuel line at as little as 350 hp. This is due to the fuel vaporizing under too much vacuum, leading to a sharp fall-off in fuel volume.
In conclusion, a 5/16 fuel line will support up to 500 HP for a carbed SBC, but it is important to consider the various factors that can affect fuel line performance when making a decision.
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A 5/16 line with 450 HP requires a 255lph pump
The suitability of a 5/16 fuel line depends on several factors, including the type of pump, type of fuel, number of g forces pulled in a straight line, and the number of sharp bends or other restrictions in the line. With a mechanical pump and pump gas, a 5/16" line may struggle to provide sufficient fuel flow for an engine with as little as 350 hp. This is because mechanical pumps put the fuel under a vacuum, pulling it forward, and if the fuel vaporizes, the fuel volume supplied to the engine decreases sharply.
Today's pump gas has a higher vapor pressure than gasoline before fuel injection was common, which makes it more susceptible to vaporization, especially when under a vacuum. However, with a carb setup, a 5/16" line can typically support up to 500 hp without issues, as the fuel bowls provide a safety net that prevents the motor from starving for fuel.
Now, let's consider your specific case of a 5/16 line with 450 HP and a 255lph pump. Based on the information provided by other users with similar setups, it appears that a 255lph pump should be sufficient for your application. One user mentioned that their friend has a 408 LS1 making 500rwhp NA and is using a single 255lph pump with upgraded wiring without any problems for the past 5 years.
Additionally, another user with a similar setup was advised by a performance specialist that a 255lph pump with upgraded wiring could support up to ~650 NA hp and about 500 FI hp. Therefore, it is safe to assume that a 5/16 line with 450 HP can be adequately supported by a 255lph pump. However, it is important to note that you may need to replace the fuel lines with bigger lines if you plan to upgrade to a twin-pump setup to achieve higher horsepower figures.
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A 5/16 line with 350 HP and a mechanical pump may cause issues
A 5/16 fuel line with 350 HP and a mechanical pump may cause issues. The type of pump, fuel, and driving conditions all influence the performance of a 5/16" fuel line. Mechanical pumps create a vacuum that pulls fuel forward, and if the fuel vaporizes, the volume decreases significantly. Modern pump gasoline has a higher vapor pressure, making it easier to vaporize, especially under a vacuum.
For example, a 5/16" fuel line with a mechanical pump and pump gas may experience issues with 350 hp or less. This is because the fuel can vaporize under too much vacuum, leading to a sharp drop in fuel volume. On the other hand, if you're using race gas with a mechanical pump, the lower vapor pressure allows you to use a smaller fuel line.
The type of driving also matters. A 5/16" line might be sufficient for a street car with occasional bursts of wide-open throttle (WOT). However, for a car that frequently experiences high horsepower and RPM, a larger fuel line is recommended. Additionally, the number of g-forces pulled in a straight line and the number of sharp bends in the fuel line can affect performance.
Some car enthusiasts recommend a 3/8" line for engines up to 450 hp, and a 1/2" line for up to 750 hp. However, others have experienced issues with a 3/8" line at around 530 hp, suggesting that a 1/2" line may be necessary in some cases. It's worth noting that a high-pressure electric pump can allow for a smaller fuel line, and an electric pump is recommended for engines over 500 hp.
In summary, a 5/16" fuel line with 350 HP and a mechanical pump may cause issues, especially with modern pump gasoline and certain driving conditions. To ensure optimal performance and avoid fuel delivery problems, it's important to consider the interplay between the fuel line size, pump type, fuel type, and driving conditions.
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A 5/16 line will limit RPM after one straight for a 318 Chrysler
A 5/16 fuel line may not be adequate for a 318 Chrysler engine, as it could limit the RPM after one straight. The Chrysler 318 engine, with its cast-iron block and heads, single camshaft, and two valves per cylinder, is a powerful motor capable of producing 230 horsepower at 4,100 rpm. To ensure optimal performance and avoid fuel pressure issues, a larger fuel line size, such as 3/8" or 1/2", is recommended.
The choice of fuel line size depends on several factors, including the type of pump, fuel, and G-forces experienced during acceleration. With a mechanical pump and modern pump gas, a 5/16" fuel line may struggle to deliver sufficient fuel beyond 350 hp. Additionally, gasoline with higher vapor pressure can vaporize easily, reducing fuel volume and causing performance issues.
For a 318 Chrysler engine, a 5/16" fuel line may not provide enough fuel volume to support high RPMs. This could result in a drop in fuel pressure, leading to decreased engine performance or even stalling. Upgrading to a larger fuel line can help ensure a consistent fuel supply and maintain the engine's power and responsiveness.
It is important to consider the intended use of the vehicle when selecting the appropriate fuel line size. For cruising at lower RPMs, a 5/16" fuel line may be sufficient. However, if the engine is frequently pushed to higher RPMs, a larger fuel line is recommended to prevent fuel starvation and maintain the engine's performance.
In summary, while a 5/16" fuel line may be adequate for some applications, it could limit the RPM and performance of a 318 Chrysler engine. Upgrading to a larger fuel line size, such as 3/8" or 1/2", is often recommended to ensure consistent fuel delivery and maintain the engine's power and responsiveness, especially when operating at higher RPMs.
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A 5/16 line is too small for performance street cars
A 5/16 fuel line may be too small for performance street cars, as it may not be able to provide enough fuel to the engine, leading to decreased performance and potential engine damage.
The size of a fuel line is important because it affects the amount of fuel that can flow to the engine. If the fuel line is too small, it may not be able to supply enough fuel to the engine, especially at high RPMs or when the car is under load. This can result in lean air-fuel mixtures, decreased performance, and potential engine damage.
For example, one user with a 69 Malibu and a 5/16 fuel line reported that their car started having problems at 7.3x @ 93.5 MPH in the 1/8th. They upgraded to a 3/8 fuel line but did not see any improvement in performance. Another user with a Camaro and a 5/16 fuel line found that their fuel pressure would drop below 3 psi in 2nd gear, which could lead to engine knock and potential damage.
Mechanical pumps, which are commonly used in performance street cars, can also contribute to the problem. These pumps put the fuel under a vacuum, pulling it forward. If the fuel vaporizes ("boils"), the fuel volume falls off sharply, reducing the amount of fuel available to the engine. This is more likely to occur with today's pump gas, which generally has a higher vapor pressure than gasoline before fuel injection was common.
To avoid these issues, it is generally recommended to use a larger fuel line, such as a 3/8 or 1/2 line, especially if the car has more than 350 hp. By upgrading the fuel line, you can ensure that the engine receives an adequate fuel supply and prevent potential performance and engine issues.
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Frequently asked questions
It depends on several factors, including the type of pump, type of fuel, number of g forces pulled, and the number of sharp bends or restrictions in the line. A 5/16 fuel line will likely support 330hp, but you may need to upgrade to a 3/8 line for higher horsepower.
The type of pump, fuel type, g-forces, and sharp bends or restrictions in the line can all impact the performance of a 5/16 fuel line. Mechanical pumps, for example, may struggle with higher horsepower due to fuel vaporization issues.
If you experience issues such as low fuel pressure, a noticeable drop in performance, or an inability to reach desired speeds, it may indicate that your 5/16 fuel line is not adequate for your horsepower requirements.
Upgrading to a 3/8 fuel line can provide increased fuel flow, reducing the risk of fuel starvation at higher horsepower. It is a common upgrade for high-performance engines and can help ensure reliable fuel delivery.
Yes, you may be able to improve fuel delivery by upgrading to a higher-capacity fuel pump or optimizing your injector sizing. It is important to consider the trade-offs, as larger pumps may be more expensive and require additional modifications.
