GM 5.7 TBI — Quick Reference & Parts Guide
Companion Reference for GM 5.7 TBI: The Practical Power Guide
This page is the working reference companion to the Bigfoot Trails Basecamp guide GM 5.7 TBI: The Practical Power Guide.
The book explains the why. This page is where I can keep the practical reference information, historical part numbers, current replacement options, tools, and other resources in one place.
Some of the information below comes from the years when I was actually building, modifying, driving, and troubleshooting GM TBI-powered vehicles. Some part numbers and recommendations are historical and may have been superseded or discontinued.
Always verify current application, specifications, compatibility, and availability before ordering a part.
350 TBI BASIC REFERENCE
Engine: Chevrolet small-block V8
Displacement: 350 cubic inches / 5.7L
Bore: 4.000 inches
Stroke: 3.480 inches
Fuel system: Throttle Body Injection (TBI)
A typical 1994–95 5.7L TBI truck engine was rated at approximately 210 hp and 300 lb-ft in lighter-duty applications, with lower horsepower ratings in heavier GVW applications. Factory ratings vary by application and rating standard.
The important thing to remember is that the factory rating isn't necessarily what the engine will actually produce at the rear wheels.
My experience: a basically stock 350 TBI combination can be surprisingly restricted by the heads, exhaust, calibration, and other factory compromises.
THE TBI THROTTLE BODY
The factory GM TBI unit is simple, durable, and capable of supporting considerably more power than many people give it credit for.
The stock throttle body is approximately 42mm.
Ultimate TBI Modification
The modification I used on my own TBI units consisted of:
Removing the ridge around the top of the throttle-body opening
Reducing the throttle-shaft thickness
Polishing the throttle bores
Using a Dremel and carbide cutting tool
Spending roughly an hour on the modification
Historical airflow figures associated with this modification were approximately:
Stock: ~450 CFM
Modified: ~500 CFM
Those figures should be considered historical estimates rather than guaranteed flow-bench results.
For a mild 350 with stock-style TBI heads, the modified factory throttle body can provide plenty of airflow.
Once the engine is capable of substantially more power, a bored/larger throttle body can become worthwhile.
Don't automatically buy a giant aftermarket TBI. Match the throttle body to the engine.
CYLINDER HEADS
The original TBI swirl-port heads were designed around emissions, low-speed torque, fuel economy, and drivability.
They are not particularly good high-flow performance heads.
Vortec Heads
The later GM Vortec heads provide a significant airflow improvement, but they require the correct Vortec-compatible intake manifold and attention to EGR and coolant-bypass requirements depending on the engine and application.
GM produced a dedicated Vortec-head intake manifold specifically designed for TBI applications, including EGR capability.
Historical GM Performance reference: 12496821 — Vortec-head-design intake manifold for TBI.
For a street-driven 350, I generally like the idea of a 165–180cc intake runner and approximately 225 CFM at .500-inch lift as a useful target rather than chasing enormous ports.
The goal is not the biggest head.
The goal is the right head for the combination.
CAMSHAFT REFERENCE
The camshaft needs to match the engine, gearing, transmission, converter, vehicle weight, and intended use.
Historical TBI cam levels used in my recommendations:
LevelDuration @ .050Approx. PowerbandLevel 1165 / 175Stock–3,200 RPMLevel 2185 / 195500–3,800 RPMLevel 3195 / 2051,000–4,500 RPMLevel 4205 / 2151,300–4,800 RPMLevel 5210 / 2201,700–5,200 RPM
The numbers above are a practical reference, not a substitute for selecting a cam based on the complete combination.
The TBI computer also isn't particularly happy trying to make useful power at extreme RPM.
Historical Cam References
GM 14097395
Comp Cams 08-409-8
Lunati 20080660
Edelbrock 3702
Edelbrock 2102
Lunati 10120200
Lunati 10120203
Lunati 10120700
Lunati 10120701
Lunati 10120702
Sealed Power CS1014R
Sealed Power CS1105R
Elgin E1100
Elgin E1127
Elgin E247
Elgin E1005P
Elgin E860S
Elgin E923
Elgin E1128
Elgin E1029
Elgin E922
Comp 12-262-4
Comp 12-236-3
Verify current availability and specifications before ordering.
ROLLER VS. FLAT-TAPPET CAMS
If I were building a new engine today, I would strongly consider a roller cam.
Advantages include:
Reduced friction
Faster valve-opening rates
Less dependence on traditional flat-tappet break-in
Better compatibility with modern engine-building practices
GM small-block blocks vary by year and application, so don't assume a particular block is ready for a factory-style roller setup simply because it is a 350.
Verify the block, lifter, retainer, distributor, timing-chain, and cam compatibility as a complete system.
EXHAUST REFERENCE
Fix the Y-pipe before buying headers.
The factory Y-pipe and catalytic-converter arrangement can be a major restriction on a TBI truck.
On one of my own trucks, improving the Y-pipe produced a very noticeable power improvement.
Headers can help once the rest of the engine can actually use them.
For a relatively mild 350, I would spend money fixing the major factory restrictions before spending money on headers.
Historical Exhaust References
Flowmaster Y250300
High-flow catalytic converters
Full Boar SS mufflers
JEGS 31102
JEGS 31006
Walker Products 90-204SS
Some of these references came from older applications and may no longer represent the best current solution.
Current exhaust parts and alternatives will be listed below as they are verified.
FUEL SYSTEM
TBI fuel systems are different from modern sequential multi-port injection.
The factory system uses injectors mounted in the throttle body and an integrated fuel-pressure regulator.
Fuel Pump
A higher-capacity fuel pump becomes important as engine airflow and horsepower increase.
Historical references include:
Stock-style GM TBI pumps
155 LPH Delphi FE0114
Verify current application before purchasing.
Injectors
Bigger injectors do not automatically make more power.
Injector size needs to match:
Horsepower
Fuel pressure
Duty cycle
Engine requirements
ECM calibration
Historical injector and fuel-pressure recommendations from older TBI builds should be treated as reference information, not universal modern recipes.
IGNITION REFERENCE
The TBI ignition system doesn't need to be complicated.
In fact, one of the lessons I learned is that adding unnecessary ignition boxes and gadgets can create more problems than they solve.
Historical References
Distributor
1992 Camaro 350 TPI Z28 distributor — historical reference for certain roller-cam applications
DUI 12620BK — historical flat-tappet reference
Coil
Pertronix D3002
Plug wires
Accel 5114K
Spark plugs
AC Delco R44TS
AC Delco R44LTS
Plug reach depends on the cylinder head being used. Verify the correct plug for the actual head.
Don't guess on plug reach.
ELECTRIC FAN REFERENCE
Electric fans can reduce parasitic load and improve control of cooling airflow, but not every aftermarket fan I've tried has impressed me.
Dual-Fan Option
A pair of factory-style GM LS1 fans is one of my preferred approaches because they provide:
Good airflow
Redundancy
OEM-style construction
Easy availability of replacement parts
Other Historical Fan Options
Lincoln Town Car fan
Ford Windstar fan
10-inch auxiliary pusher fan
Basic Wiring Reference
Historical installations used:
One relay per fan
Properly sized fuse protection
Key-on relay trigger
Heavy-gauge power wiring
Good grounds
Fuse, relay, wire size, and connector selection must be based on the actual fan's current draw and the wiring installation.
Do not blindly duplicate an old fuse size because it appeared in an older article.
FUEL-MILEAGE REFERENCE
The cheapest mileage modification is still the driver.
Start Here
Slow down
Avoid jackrabbit acceleration
Use reasonable throttle
Keep unnecessary weight out of the vehicle
Maintain proper tire pressure
Fix mechanical problems
Keep the engine properly tuned
Other Factors
Tire size: Large tires add weight and rolling resistance.
Ride height: Raising a truck can increase aerodynamic drag.
Speed: Aerodynamic drag increases rapidly with speed. Around 70 MPH is an important practical dividing line for many trucks.
Gearing: An overdrive transmission helps tremendously, but excessively low cruising RPM isn't automatically better.
Electric fan: Can reduce parasitic load when properly matched to the cooling system.
Exhaust: Reducing major restrictions can improve engine efficiency.
Tuning: A properly calibrated ECM can improve drivability and efficiency.
Engine temperature: Do not arbitrarily increase operating temperature or radiator-cap pressure. Use the temperature and cooling-system specifications appropriate to the engine and vehicle.
GEARING & CRUISING RPM
Historical street recommendations:
3.42: Reasonable for a mild combination
3.73: Excellent all-around street performance gearing
4.10: Useful when acceleration, towing, tire size, or a specific combination calls for it
For many overdrive street combinations, approximately 2,000–2,400 RPM at 70 MPH is a useful general target.
That is not a universal rule.
Tire diameter, transmission gearing, engine torque, vehicle weight, camshaft, and intended use all matter.
General Rule
If the engine is constantly below its useful powerband, it may lug, downshift, and use more throttle than expected.
If it is turning unnecessarily high RPM on the highway, fuel economy suffers.
Match the gearing to the engine.
TORQUE CONVERTERS
The stock converter is often conservative.
A modest increase in stall speed can help an engine with a larger camshaft get into its useful powerband.
Historical reference:
1995+ S-10 4.3L V6 converter
Approximately 2,000–2,200 RPM stall in certain applications
Again, converter selection depends on the entire combination.
For a truck used heavily for towing, off-road driving, or low-speed work, I would not automatically install a high-stall converter.
THINGS I WOULD NOT SPEND MONEY ON FIRST
Before buying expensive parts, fix the restrictions that are already there.
I would not start with:
Giant aftermarket TBI units
Random mail-order chips
Bigger injectors simply because they're bigger
454 injectors on a mild 350
Expensive roller rockers for minimal expected gain
Headers before fixing a restrictive Y-pipe
Exotic spark plugs
Cheap ignition components
Huge cams
High-volume oil pumps without a reason
Expensive parts that don't match the rest of the combination
Build the combination — not the parts list.
HISTORICAL PART NUMBER REFERENCE
The following numbers appeared in my older GM TBI work and are retained because they can still be useful for identifying components, researching old builds, or finding equivalent parts.
Fuel
Delphi FE0114 — historical higher-capacity fuel-pump reference
Ignition
Pertronix D3002 — coil
Accel 5114K — plug wires
AC Delco R44TS — spark plug
AC Delco R44LTS — spark plug
1992 Camaro 350 TPI Z28 distributor
DUI 12620BK
Camshafts
GM 14097395
Comp 08-409-8
Lunati 20080660
Edelbrock 3702
Edelbrock 2102
Lunati 10120200
Lunati 10120203
Lunati 10120700
Lunati 10120701
Lunati 10120702
Sealed Power CS1014R
Sealed Power CS1105R
Elgin E1100
Elgin E1127
Elgin E247
Elgin E1005P
Elgin E860S
Elgin E923
Elgin E1128
Elgin E1029
Elgin E922
Comp 12-262-4
Comp 12-236-3
Exhaust
Flowmaster Y250300
JEGS 31102
JEGS 31006
Walker Products 90-204SS
Intake / Vortec
GM 12496821 — Vortec-head-design intake manifold for TBI
Important: Historical part numbers are provided for reference and research. Availability, fitment, specifications, and supersession can change.
CURRENT PARTS & RESOURCES
This is where I'll maintain current information as I verify it.
TBI / Airflow
Current parts and tools:
[Add verified links here]
Fuel System
Current fuel-pump options:
[Add verified links here]
Current injector options:
[Add verified links here]
Ignition
Current ignition components:
[Add verified links here]
Camshafts
Current camshaft options:
[Add verified links here]
Exhaust
Current Y-pipe and exhaust options:
[Add verified links here]
Electric Fans
Current fan, relay, wiring and control options:
[Add verified links here]
BEFORE YOU ORDER
Some of the components discussed in this guide are from the era when these trucks were new.
That means:
Part numbers may have changed.
Manufacturers may have discontinued products.
Modern replacements may have different specifications.
Parts that look similar may not actually be compatible.
Different model years and applications can use different components.
Verify the actual application before ordering.
The purpose of this reference is to help you understand what you're looking for—not to replace the vehicle's service information or the manufacturer's current application data.
THE BOTTOM LINE
The GM 5.7 TBI isn't a modern LS engine.
It doesn't need to be.
It's a simple, durable small-block with a basic electronic fuel-injection system that can do considerably more than the factory combination suggests.
Fix the restrictions.
Match the parts.
Get the fuel and ignition right.
Choose the cam for the vehicle.
Tune the combination.
And don't spend $1,000 trying to solve a problem that a $100 part—or a little work with a grinder—could have fixed.
Build the combination. Not the parts list.
About Bigfoot Trails Basecamp
Bigfoot Trails Basecamp | Independent Adventure Media
Bigfoot Trails Basecamp is about real-world adventure, vehicles, motorcycles, RVs, technical projects, travel, and the lessons that come from actually doing the work.
Adventure isn't a product. It's an experience.