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Alfa Romeo GTV6 Development Mule Purpose: Track/street development platform; validation of bespoke high-performance systems
Chassis: 1982 Alfa Romeo GTV6 (116-series)
This document consolidates the core specifications and engineering decisions for my GTV6 project. It is a living reference and the result of decades of research, parts accumulation, and collaboration with some of the best minds in the Alfa Romeo community.
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Project Vision & PhilosophyThis is not a restoration. This is a complete re-engineering of the GTV6 platform with a "Singer-rival" ethos. The goal is to preserve the soul and character of the Alfa Romeo V6 while applying modern materials, electronics, and fabrication techniques to create a reliable, high-revving, and uncompromising driver's car. Every system has been evaluated, and where the factory components reached their physical limits, bespoke solutions were engineered.
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1. Engine Core — 4.04L 12-Valve Busso V6
The foundation is a 3.0L 12-valve block, significantly reinforced and stroked.
Component Specification Notes
Block Alfa Romeo 3.0L 12V, aluminum open-deck Deck height ~205.6mm (to be precision measured)
Bore 98 mm (target); 101 mm evaluated Darton MID sleeves or equivalent planned
Stroke 84 mm Offset-ground, welded, and re-nitrided 3.2L crank (Honda B-series rod journals)
Displacement 3,801–4,038 cc Final displacement dependent on bore selection
Compression Ratio 13.2:1 Optimized for flex fuel (93 pump to E85)
Compression Height 25 mm Enabled by custom 18mm DLC-coated titanium wrist pins (39g each)
Connecting Rods Custom 133–136 mm, 18mm pin bore 4340 steel, pressure-fed pin oiling
Pistons Custom forged 2618-T6 flat-top with dish 1.0/1.2/2.8mm low-tension gas-ported ring pack
Head Gaskets Cometic custom MLS or copper O-ringed block with stainless wire
Main Caps Billet steel girdle Integrated with oil pan for bottom-end rigidity
Crankshaft Alfa 3.2L core Weld/grind/re-nitride to 84mm stroke; Honda B-series bearings
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2. Cylinder Heads & Valvetrain
The cylinder heads are a cornerstone of the build, prepared by the legendary Richard Jemison.
Component Specification Notes
Heads Alfa Sei 2.5L carbureted downdraft Richard Jemison-built; 41mm intake ports
Chamber Volume 44–46 cc (est.) To be CC'd for final compression calculation
Camshafts Richard Jemison custom SOHC grinds .616"/.431" lift; timed via Jemison wire-tie method
Cam Gears Erich Stahlman adjustable 2-piece Installed
Intake Valve 44.0 mm Ti-6Al-4V 6mm waisted stem, CrN coated
Exhaust Valve 38.5 mm Inconel 751 6mm waisted stem, sodium-filled optional
Valve Springs Custom beehive 90–105 lb seat, 300–325 lb open; 32.5mm installed height
Rocker Arms Custom 7075-T6 billet Target 1.6:1 ratio (OEM ~1.3:1)
Spark Plugs Champion surface discharge No ground electrode protrusion
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3. Induction, Fuel & Power Adders
Component Specification Notes
Throttle Bodies 50 mm FAJS downdraft ITBs Individual runner; no plenum
Injectors Bosch 1150cc Pico (EV14) E85 compatible; native Autronic SM4 characterization
Fuel Type Flex fuel (93 pump to E85) GM 12685371 Continental sensor (ethanol % + fuel temp)
Fuel Pumps AEM 400 primary; staged secondary Controlled via SM4 (Pin 13 / Pin 20)
Fuel Pressure Aeromotive FPR 200 PSI transducer for monitoring and safety
Water-Methanol Dual-stage Stage 1 fogging (Pin 14), Stage 2 direct port (Pin 28); 5-gallon reservoir
Nitrous Oxide 300 hp dry shot Fuel enrichment via injectors; progressive SM4 control
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4. Engine Management & Electronics
The central nervous system is built around the Autronic SM4 ECU and Racepak V-Net CAN bus.
Component Specification Notes
ECU Autronic SM4 (v1.09) Per-cylinder knock, flex fuel, traction control
Multiplexer Autronic 568 Expands SM4 to 6 sequential ignition outputs
Ignition MSD Pro 600 CDI MSD 8280 coil-on-plug; uninterrupted 12 AWG silver-plated twisted shielded primaries
PDM Racepak SmartWire (230-VM-SW) Solid-state power distribution; V-Net CAN
Dash/Logger Racepak IQ3S / G2X V-Net CAN integration
Interface 230-VM-EFIAUT4 Converts SM4 serial to V-Net CAN
Switch Panels 500-SW-SM16 (16-position) + 500-SW-PNL8 (8-button) Full vehicle control
Alternator GM AD244 253-amp PWM controlled via SM4 Pin 34
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5. Drivetrain
Protecting the Alfa 116 transaxle while handling over 600 hp (with nitrous) required a multi-layered approach.
Component Specification Notes
Transaxle Alfa 116 synchromesh (Milano Verde core) Lightened, cross-drilled gears
Differential Factory LSD Shimmed to 50% lock-up (Kartalamakis method)
Intermediate Plate Custom 1/2" 4140 tool steel Replaces factory plate to eliminate case flex
Clutch Tilton OT-140 5.5" cerametallic 3-plate Custom flywheel (3D scan and duplicate required)
Driveshaft PST custom one-piece carbon fiber Scuderia Giallo GT3 reference; eliminates guibo
Shift Strategy Strain-gauge shift cut via SM4 Synchro protection; 150ms resume delay
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6. Chassis & Suspension
Extensive chassis reinforcement and a complete re-engineering of the front suspension geometry.
Component Specification Notes
Chassis Tube-frame conversion 10-point cage; A-pillar hoop; door crossbeam; stitch-welded seams
Engine Position 6" rearward, 2" downward Custom mounts; improves weight distribution
Pedal Assembly Tilton 72-618 3-pedal underfoot Clutch, brake, throttle; firewall relocated
Steering Milano rack (2.7 turns) + Volvo electric pump Speed-sensitive EPAS via SM4 Pin 7 PWM
Front Uprights Custom 7075-T6 billet Designed for OEM C7 Corvette front hubs
Front Hubs C7 Corvette (GM 23291487) 5x120.65 PCD; 70.3mm hub bore; integrated ABS encoder
Front Suspension 27.3mm Supersport torsion bars; 27mm sway bar; spherical end links
Rear Suspension De Dion with SZ spherical pivot; 5" coilovers (150/175/225 lb/in) Watt's link with spherical center pivot
Wheels Corvette C5/C6/C7 18x9.5" Direct fit via custom hubs
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7. Braking System
A two-tier braking strategy for development and final specification.
Component Development Spec Customer Spec
Front Rotors Alcon PR 2008 328x40mm iron (3 pairs in stock) AP Racing 378x35.6mm (1 pair NEW)
Front Calipers Alcon PSC4412 6-piston Alcon PSC4412 6-piston
Front Pads Porterfield R4-S Porterfield R4-S
Rear Rotors Stock diameter, vented, 22mm Stock diameter, vented, 22mm
Rear Calipers OEM with Performatek vented spacers OEM with Performatek vented spacers
Rear Pads Porterfield R4-S Porterfield R4-S
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8. Cooling & Climate Control
Component Specification Notes
Water Pump Meziere WP337 12V remote electric AN -12 fittings; SSR controlled
Radiator C&R NASCAR (Richard Childress #17) Integrated oil cooler; AN -20 bottom feed
Thermostats C&R remote (dual) AN -12; Volvo elements; AN -4 bleed to vented tank
Coolant Laboratory-grade non-aqueous propylene glycol (5 gal) Zero-pressure vented system
A/C Compressor Treeligo 12V electric Right rear bumper mount; SmartWire controlled
A/C Evaporator Vintage Air trunk-mount Relocated to behind rear seat; blows forward
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9. Fuel System (Relocated)
Component Specification Notes
Tank Custom 20-gallon aluminum Right rear corner, under trunk floor; E85 compatible
Heat Shielding 321 stainless divider wall Coated; air gap; isolates trunk from exhaust
Exhaust SZ shorty-style headers (Bill Sims 330 whp validated) 4" 321 stainless; wrapped and coated; routed away from fuel system
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10. Key Technical Contacts & Provenance
This build stands on the shoulders of giants in the Alfa Romeo community.
Name Contribution
Richard Jemison Sei heads, custom camshafts, cam timing method, 164S pistons
Peter Dawe (DAWE Motorsports) Mentor; foundational knowledge in Porsche-level engineering and fabrication
Jim Kartalamakis The Alfa Romeo V6 Engine High-Performance Manual; LSD shimming
Bill Sims 330 whp validation for SZ shorty headers
Scuderia Giallo Alfa GT3 SCCA racer; PST carbon driveshaft reference
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11. Current Status & Critical Path
The project is in the fabrication and assembly planning phase. Core components are in hand; the focus is on precision measurement and custom machining.
Priority Action Item
1 3D scan custom Tilton flywheel (fabricator deceased)
2 Source and prepare 3.2L crankshaft (weld/grind/re-nitride)
3 Precision measure block deck height and CC combustion chambers
4 Order custom connecting rods and pistons
5 Fabricate billet valve covers with integrated coil mounts
6 Fabricate front (water pump) and rear (bellhousing) bulkhead plates
7 Complete chassis stitch welding and 10-point cage installation
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This document will be updated as the build progresses. Questions and technical discussion are welcome.