Build catalogue
Ken Hiebert's 1972 TR-6 with LT1 5.7L EFI Engine
britishv8.orgas published in British V8 Newsletter, Volume XV Issue 2, September 2007
Photo: britishv8.orgA 1972 Triumph TR6 rebuilt with a GM LT1 5.7L EFI V8
Ken Hiebert swapped the six-cylinder in his TR6 for an unmodified 1994 GM LT1 EFI V8 pulled from a Pontiac Trans Am, carrying over most of the donor car's wiring, ECM and instrumentation. He reworked the frame, suspension, brakes and driveline to suit, and kept refining the car over several years, with dyno-proven power gains and thousands of kilometres of hard driving including autocross and track days.
Specs
As the owner states it.
- Engine
- Unmodified 1994 GM LT1 5.7L EFI from a Pontiac Trans Am
- Fuel System
- Fuel pump mounted in the tank with a modified fuel level sender unit
- Cooling
- 4-row crossflow radiator from a 1969 Firebird, Ford minivan fan and shroud
- Exhaust
- Jet Hot coated hugger headers into 2.25 inch stainless steel dual exhaust, routed through the frame
- Transmission
- Borg-Warner T56 6-speed manual, first gear 2.66:1, 5th and 6th overdrive; stock GM clutch with hydraulic actuation
- Front Suspension
- TR6 with polyurethane bushings, lowering spacers on lower control arms, sway bar routed above front skid plate
- Rear Suspension
- Narrowed 8 inch Ford axle with 3.55:1 gear on leaf springs, Panhard bar and custom slide-a-link traction bars
- Brakes
- Stock TR6 front brakes with line lock electric solenoid, Ford rear with proportioning valve
- Frame Mods
- Double-boxed frame rails, removable secondary crossmember, new center section for through-the-frame exhaust, rear frame replaced from seats back to accommodate leaf springs and roll hoop
- Wheels/Tires
- 1986 Ford Mustang Cobra 15x7 wheels, redrilled front hubs with 3/4 inch spacers, 215/60 front and 225/70 rear tyres
- Electrical
- Pontiac Trans Am wiring, circuit protection, ECM and instrument panel, GM/Delphi Packard Metri-Pack connectors
- Steering Column
- Pontiac Fiero tilt column with GM VATS anti-theft ignition key tumbler
- AC System
- Vintage Air climate unit with heat and defrost, GM (Harrison) compressor
- Performance Data
- 255 hp and 301 ft-lbs torque at the rear wheels (9/18/2007 dynojet); 1600rpm at 70mph in 6th gear; approx 25mpg city and 30mpg highway (Canadian gallon)
- Date Completed
- First run Christmas Eve 2006, driven 5000km as of British V8 2007 meet
- Front Suspension (update)
- Upper control arms modified for 4.5 degrees total castor, custom bump stops, Heim joints replacing tie rod ends
- Brakes (update)
- Wilwood 4-piston front calipers with 12.25 inch vented rotors
- Frame Mods (update)
- Custom double roll hoop with wind blocker
- Wheels/Tires (update)
- Mustang Cobra R 17 inch wheels, front hubs redrilled to Ford pattern, 245/45R17 tyres
- Interior (update)
- Mazda Miata seats and seat belts
- Performance Data (update)
- 273 hp max power and 359 ft-lbs max torque at the rear wheels, measured 6/8/2009 at Carolina Auto Masters
- Miles Driven
- 37,000km as of October 2009
Parts used
What the owner names in the write-up, grouped the way the Parts page groups them. Where one of the shops we index lists the same thing for this car, it is shown underneath with a link to the shop.
Shop suggestions are being prepared. The owner's parts list is available below.
Engine 3
- 1994 GM LT1 5.7L EFI V8 engineGM
Unmodified engine from a Pontiac Trans Am used as the swap powerplant
- Jet Hot coated hugger headersJet Hot
Routed into the through-the-frame exhaust system
- 2.25 inch stainless steel dual exhaust
Routed through the frame for ground clearance
Fuel & Ignition 3
- In-tank fuel pump with modified fuel level sender
Supplies fuel to the EFI engine, sender modified to fit the TR6 tank
- Pontiac Trans Am throttle bodyPontiac
Retained from donor car for EFI induction
- K&N air filterK&N
Fitted to the engine's intake
Cooling 2
- 4-row crossflow radiator from 1969 Firebird
Provides cooling capacity for the V8 swap
- Ford minivan fan and shroudFord
Used with the Firebird radiator for cooling airflow
Gearbox & Drivetrain 2
- Borg-Warner T56 6-speed manual transmissionBorg-Warner
First gear 2.66:1, fifth and sixth are overdrives; stock GM clutch with hydraulic actuation
- Narrowed 8 inch Ford rear axle, 3.55:1 gearsFord
Rear axle on leaf springs with Panhard bar location
Suspension & Steering 7
- Polyurethane suspension bushings
Fitted to TR6 front suspension
- Lower control arm lowering spacers
Added to reduce ride height
- Panhard bar
Locates the rear axle
- Custom slide-a-link traction bars
Controls axle wrap under power
- Heim joint tie rod ends
Replaced stock tie rod ends to reduce bump steer
- Custom bump stops
Fabricated to limit suspension travel
- Pontiac Fiero tilt steering columnPontiac
Fitted with GM anti-theft VATS ignition key tumbler
Brakes 3
- Line lock electric solenoid
Fitted to stock TR6 front brakes
- Ford rear brakes with proportioning valveFord
Balances braking front to rear
- Wilwood 4-piston front calipers with 12.25 inch vented rotorsWilwood
Front brake upgrade fitted in later update
Wheels & Tyres 2
- 1986 Ford Mustang Cobra 15x7 wheelsFord
Original wheels, front hubs redrilled with 3/4 inch spacers, 215/60 front and 225/70 rear tyres
- Mustang Cobra R 17 inch wheelsFord
Later wheel upgrade with 245/45R17 tyres, front hubs redrilled to Ford pattern
Body & Trim 1
- Custom double roll hoop with wind blocker
Replaced earlier roll hoop for safety and styling
Interior 2
- Vintage Air climate control unitVintage Air
Provides heat, defrost and air conditioning
- Mazda Miata seats and seat beltsMazda
Fitted in later interior update
Electrical 5
- Pontiac Trans Am wiring harness and electrical centerPontiac
Reused donor car wiring, fuses and relays for the swap
- Pontiac engine control module (ECM)Pontiac
Controls EFI engine, retained from donor car
- GM/Delphi Packard Metri-Pack connectorsDelphi
Used throughout wiring for reliability, including firewall pass-thru
- Delco-Remy alternatorDelco-Remy
Charging system component from donor car
- GM (Harrison) AC compressorHarrison
Drives the air conditioning system
Photos
All 40 pictures in the write-up, in the order they were posted, shown from britishv8.org. A picture opens larger here, with the way through to the page it is on.
How it was done
Choosing and fitting the LT1
Ken installed an unmodified 1994 GM LT1 5.7L EFI engine, sourced from a Pontiac Trans Am, into his TR6. The swap kept the engine largely stock, relying on the LT1's reverse-flow cooling design that cools the heads first, allowing higher compression without detonation.
Cooling and fuel
A 4-row crossflow radiator from a 1969 Firebird was fitted along with a minivan fan and shroud to handle the V8's cooling needs. The fuel system used an in-tank pump with a modified fuel level sender to suit the EFI engine.
Exhaust and driveline
Jet Hot coated hugger headers feed into a 2.25 inch stainless dual exhaust routed through the frame for ground clearance. Drive goes through a Borg-Warner T56 six-speed manual with hydraulic clutch actuation to a narrowed 8 inch Ford rear axle with 3.55:1 gears, located by a Panhard bar and custom slide-a-link traction bars.
Frame and suspension work
The frame rails were double-boxed and a removable secondary crossmember added to tie the motor mounts together. A new center frame section was fabricated for the raised through-the-frame exhaust, and everything from the seats back was replaced with a new structure to suit leaf springs and the roll hoop. Front suspension kept TR6 geometry with polyurethane bushings, lowering spacers, and a relocated sway bar.
Brakes, wheels and electrical
Stock TR6 front brakes were retained initially, with a line lock solenoid, and a Ford rear setup with a proportioning valve. Wheels were 1986 Ford Mustang Cobra 15x7s on redrilled front hubs. Most of the Trans Am's wiring, fuse and relay center, ECM and instrument panel were reused, giving cruise control and diagnostics, along with a Pontiac Fiero tilt steering column and Vintage Air climate system.
Sorting a driveline noise
After first running the car on Christmas Eve 2006, Ken chased a chirping noise from the custom serpentine belt system, at first suspecting the alternator or idler pulleys. It turned out the harmonic balancer spacing was slightly off, and correcting that alignment solved the noise.
Later updates
Over the following years Ken added castor to the front suspension, fitted Heim joints to cut bump steer, made custom bump stops, and upgraded to Wilwood 4-piston front calipers with 12.25 inch rotors. He also fitted a custom double roll hoop with wind blocker, Mustang Cobra R 17 inch wheels, and Mazda Miata seats and belts, with the car dyno tested again in 2009.
A summary in our own words. The full account, with all its detail, is the owner's: read it at britishv8.org ↗
Worth knowing
- Check harmonic balancer spacing carefully when building a custom serpentine belt system to avoid chirping noises.
- Reusing the donor car's wiring, ECM and connectors can preserve factory features like cruise control and diagnostics.
- Routing the exhaust through the frame can raise ground clearance but requires reworking the frame's center section.
- Adding castor and Heim joints to the front suspension can meaningfully reduce bump steer.
- Upgrading brakes and wheels after the initial build lets you address handling limits found through real track and autocross use.