Sylvie Willis
The TPI fuel injection system is a popular choice for car enthusiasts, with many opting to retrofit older engines with this technology. While it is not overly complex, it does require a good understanding of basic induction systems, as well as computerized controls and circuitry. Upgrading the ECM system can improve reliability, tuneableness, and fuel economy. Rebuilding a Chevy TPI fuel injector can be a cost-effective option, with some services offering injector rebuilds for as little as $11 per injector. However, it is important to be aware of potential issues with the TPI system, such as poor gas mileage and cold start problems.
| Characteristics | Values |
|---|---|
| Engine | Chevy 350 TPI engine |
| Year | Early 1986 |
| Parts | Cast iron heads, Turbo 350, 2.79 open rear end, Aftermarket ECU, 'street' tune chip, Wiring harness |
| Issues | Poor gas mileage (10 mpg), Pinging under load |
| Upgrade options | New aftermarket EFI system, Better heads, Cam, Rockers, Pushrods, Gaskets |
| TPI system | High-tech, Requires knowledge of basic induction systems, computerized controls and circuitry |
| TPI fuel rail | TPI runners |
| Fuel injector options | Remanufactured injectors, Rebuild service |
| TPI intake | TPIS MiniRam, Edelbrock pro flow xt, Holley Weiand stealth ram |
| TPI modifications | Cold start injector, Intake manifold, Camshaft, Fuel injector O-ring kit, Fuel filter |
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$890.17 $964.71
$277.54
What You'll Learn
Step-by-step guide to retrofitting a TPI system to a Chevy small-block motor
Retrofitting a TPI system to a Chevy small-block motor can be a complex process and requires a good deal of knowledge of basic induction systems, computerized controls, and circuitry. Here is a step-by-step guide to help you through the process:
Step 1: Understand the Basics
Before starting the retrofit process, it is essential to have a good understanding of how the TPI system works. Familiarize yourself with the basic induction systems, computerized controls, and circuitry involved in the TPI system. This knowledge will be crucial as you move forward with the retrofit.
Step 2: Consult a Specialist
Before making any major engine changes to your Chevy small-block motor, it is highly recommended to consult a specialist. A specialist can provide valuable advice and guidance to ensure that you are on the right track and can help you avoid potential pitfalls or problems during the retrofit process.
Step 3: Source the TPI Components
You will need to gather all the necessary TPI components for the retrofit. You can source these components from various places, such as swap meets, salvage yards, or aftermarket dealers. Keep in mind that there are variations in TPI systems from year to year, so ensure that you are getting compatible parts. Alternatively, you can consider purchasing a complete setup, including manifolds, sensors, harness, and fuel pump, from a single-donor car at a salvage yard.
Step 4: Prepare the Fuel Pump
A TPI system requires a minimum fuel pressure of 40-45 psi, so it is essential to have an electric fuel pump. You can adapt an in-tank pump from a factory system or use an aftermarket tank with baffling or an external pump with a fuel reservoir. Regardless of your choice, ensure that the fuel feed line is plumbed for high-pressure operation.
Step 5: Follow a Detailed Guide
For a step-by-step guide specifically tailored to retrofitting a TPI system to a Chevy small-block motor, consider investing in a manual or guide book. Former Car Craft Editor John Baechtel's "Chevy TPI Fuel Injection Swappers Guide" and Mike Knell's "Chevrolet TPI & TBI Engine Swapping" manuals are highly recommended and provide valuable information and tips for the retrofit process.
Step 6: Consider Upgrades and Modifications
As you work on retrofitting the TPI system, consider making upgrades or modifications to enhance the performance, fuel economy, and reliability of your Chevy small-block motor. This could include upgrading the ECM system, converting to a Megasquirt system, or investing in a decent set of heads and a camshaft.
Remember, this process can be complex, and it is important to have a good understanding of the systems involved. Take your time, consult specialists when needed, and always prioritize safety when working on your vehicle.
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Pros and cons of buying remanufactured injectors vs. rebuilding them
Remanufactured fuel injectors are those that have been disassembled, checked for wear, and rebuilt with new components. They are also referred to as rebuilt injectors. On the other hand, refurbished injectors are advertised as having their worn-out parts replaced.
Pros of buying remanufactured injectors:
- They are cheaper than buying a brand-new injector.
- They are rebuilt using brand-new components.
- They come with a warranty.
- They are rigorously tested on state-of-the-art test stands to ensure they meet OEM specifications.
Cons of buying remanufactured injectors:
- They may not always be of the best quality, depending on the shop you're buying from.
- Deceptive labeling is common in the auto parts industry, with some shops selling lesser-quality injectors as "remanufactured".
Pros of rebuilding injectors:
- You can ensure that the injectors are rebuilt according to your requirements.
- You can ensure that the rebuilding is done by skilled technicians with the right equipment and knowledge.
Cons of rebuilding injectors:
- Rebuilding services may not always be cheaper than buying remanufactured injectors.
- It may be difficult to judge the quality of the rebuilding job, as it depends on the workshop's standards and the technicians' skills.
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Recommended modifications to the TPI system
The TPI system has several recommended modifications that can improve performance and efficiency. Here are some detailed suggestions:
Firstly, the cold start injector, also known as the 9th injector, is considered the worst piece of the TPI system. It is recommended to get a block-off kit to remove it, which will solve many cold start issues. This can be purchased from eBay, along with a custom PROM chip to program the remaining eight injectors to run smoothly.
Secondly, the intake manifold is often criticised for its design, which can cause vacuum leaks and limit top-end power potential. Changing to an aftermarket intake, such as the TPIS miniram or the Edelbrock pro-flow xt, can cure issues with TPI intakes and improve performance. Modifying the stock TPI intake base by shortening the effective intake runner length is also an option if you're on a budget.
Thirdly, the camshaft is another area for potential modification. It is recommended to stay with a roller cam unless you are drag racing, and consider a roller motor like a 1996 vortec truck roller for better flowing heads.
Additionally, for those seeking more power, a custom PROM chip, larger injectors (30-pound injectors are recommended), and a higher-capacity, in-tank fuel pump to support the larger injectors are suggested.
Finally, some general modifications include freeing up the exhaust side, installing better cylinder heads, or sliding in a bigger cam. For those seeking to retain the stock appearance, converting to a sequential EFI, a larger throttle body, and improving airflow with long-tube headers are recommended.
It is important to note that some of these modifications may require significant changes to the engine setup, such as a new wiring harness, sensor suite, and computer system. Careful planning and consideration of your specific engine configuration are essential before making any modifications.
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Common issues with the TPI system
The TPI system is generally reliable, but as with any technology, issues can arise. Here are some common problems that users have reported:
Vacuum Leaks: These can cause havoc on a MAF system, allowing unmetered air into the intake and causing idle and off-the-line issues. It is important to test for vacuum leaks and address them promptly to ensure the TPI system functions optimally.
Fuel Pressure and Injector Issues: Some users have reported problems with fuel pressure, such as low pressure in the fuel rails or fluctuations in pressure. This could be due to various factors, including a faulty fuel pump, a blocked fuel line, or issues with the fuel injectors themselves. It is recommended to check for spark and pulse at the injectors, as a bad ignition module could be the culprit.
Incompatible Components: When combining TPI with classic Chevys, it is important to ensure that the components are compatible. For example, an 87 wiring harness and computer are not compatible with a MAP sensor due to differences in wiring and computer input/output ports.
Poor Gas Mileage and Performance: Some users have reported issues with poor fuel economy and performance, such as pinging under load. This could be due to various factors, including incorrect tuning, vacuum leaks, or other underlying mechanical issues.
Age of the System: The TPI system is over 30 years old, and while it was state-of-the-art when introduced, it may not match the performance and efficiency of modern fuel injection systems. Upgrading to a newer system may be considered, but it is important to consult with specialists to ensure compatibility and avoid costly mistakes.
While the TPI system generally has a good reputation for reliability, addressing these common issues can help ensure optimal performance and longevity.
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Upgrade options for the TPI system
Upgrading the TPI system of a Chevy 350 TPI engine can be a complex task, requiring knowledge of induction systems, computerized controls, and circuitry. While some opt to retain the stock TPI system, there are several upgrade paths to consider. Here are some options to enhance performance and address common issues:
- Upgrading the ECM system: This can improve reliability, tuneability, and fuel economy. A Megasquirt conversion, for instance, can be achieved for less than $1000.
- Modifying the stock TPI intake base: Shortening the effective intake runner length by cutting out a section of aluminum between the intake runners can increase power output.
- Exhaust modifications: The restrictive nature of the stock exhaust can hinder performance, especially when aiming for higher horsepower levels. Upgrading to a Flowmaster Y250300 collector can address this issue.
- Camshaft considerations: It is recommended to stay with a ROLLER CAM for street-driven vehicles. For those running a speed density Map sensor-based 1990-1992 TPI system, a larger lobe separation angle is advisable to minimize tuning complexities.
- Fuel injectors and pump: Upgrading to 30-pound injectors, such as those made by Bosch, can enhance performance. However, this requires a higher-capacity, in-tank fuel pump like the Quantum bolt-in fuel pump to support the larger injectors.
- Cold start injector issues: The 9th injector, also known as the cold start injector, is often problematic. A solution is to use a block-off kit to remove it and reprogram the chip to run with the remaining eight injectors.
- Intake manifold: The unique design of the TPI intake manifold can be a bottleneck for performance. While some appreciate its looks, it is prone to vacuum leaks and limits top-end power potential.
- AIR pump deletion: For off-road use, an AIR pump delete kit can be employed to maintain proper belt tension and pulley belt-wrap while removing the smog pump.
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