juggernautjoee's 1974 Datsun 260Z build

juggernautjoee · 1974 Datsun 260Z

Datsun 260Z (S30)6-page write-up

Early 1974 260z build (HybridZ)

Read the full write-up at Early 1974 260z build (HybridZ) ↗

Photo: Early 1974 260z build (HybridZ)

A 1974 Datsun 260Z turned turbo L28, rebuilt through a stubborn fuel and head saga

juggernautjoee bought an early 1974 260Z described as running, then spent years chasing a fuel delivery fault, a cracked exhaust valve, a bad head, and later converted the car to turbo power with a Megasquirt standalone. Along the way the suspension, brakes, differential, and interior were also updated. The thread shows a long, honest, partially finished project rather than a polished result.

Specs

As stated in the original write-up.

Engine: L28 inline six, N47 head fitted after original P90 head cracked, later upgraded to a machined P90A head
Carburetion/Fuel system (early): Round-top SU-style carbs initially, later converted to turbo with Megasquirt EFI
Ignition: 280ZX non-turbo distributor installed to remove points, later tuned via Megasquirt
Rear axle: Subaru R180 with limited slip differential
Suspension: BC Racing coilovers with polyurethane bushings
Wheels/Tyres: New wheels and tyres fitted
Alternator: Internally regulated unit from a 1999 Nissan Pathfinder
Harmonic balancer: Pro Products PowerForce damper, part 90055
Weight: 2680 lbs as weighed with driver and full fluids
Body: 240Z bumpers fitted in place of 260Z bumpers
Interior: Full carpet and butyl sound deadening throughout except doors, HVAC components removed from dash

Parts used

Parts named as used in the original 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.

Engine 9

Schneider camshaft regrind
Extra turbo cam sent out for regrind and installed
In the shops
Factory Camshaft Performance Regrind, 70-83 240Z/260Z/280Z/280ZX Non-Turbo ↗Motorsport Auto (The Z Store)· $339.87
Factory Camshaft Performance Regrind, 70-83 240Z/260Z/280Z/280ZX Non-Turbo ↗Motorsport Auto (The Z Store)· $339.87
Camshaft Performance Regrind ↗Motorsport Auto (The Z Store)· $339.87
Schneider valve springs and retainers
Ordered for the rebuilt head
In the shops
Valve Spring Retainer, Titanium ↗Good Parts· $21.00 USD
Timeserts
Installed in head to repair threads
P90A cylinder head
Sourced, machined (0.007in off for warp) and fitted with valve job
In the shops
Cylinder Head Heater Connector for Nissan L6 Engine ↗JDM Car Parts· $49.99 USD
Cylinder Head Gasket Set (Rover V8 Carb) ↗bpnorthwest.com· $59.99 USD
Water Pump Housing to Cylinder Head Gasket ↗bpnorthwest.com· $0.69 USD
Godzilla Raceworks cooling head mod kit
Installed on the head for cooling improvement before reassembly
eBay exhaust header
Fitted but found incompatible with carbureted intake manifold
MSA turbo downpipe
Painted, wrapped and installed on the turbo setup
In the shops
MSM Turbo Outlet-to-Downpipe Gasket (2004-05) ↗Flyin' Miata· $29.99 USD
MSA Performance Cat-Back Exhaust System (84-85 300ZX Non-Turbo) ↗Motorsport Auto (The Z Store)· $249.87
HKS blow-off valve
Used black HKS BOV fitted to the turbo system
In the shops
HKS SSQV4 Blow-Off Valve Kit ↗JDMuscle — Mazda MX-5· $1,320.00 USD
HKS Super SQV 4 Blow-Off Valve Kit ↗JDMuscle — Mazda MX-5· $570.00 USD
HKS Super SQV 4 Replacement Blow-Off Valve Kit ↗JDMuscle — Mazda MX-5· $570.00 USD
Pro Products PowerForce harmonic damper (90055)
Aftermarket balancer fitted after distrust of the stock unit's timing marks
In the shops
SFI Harmonic Damper Balancer ↗Z Car Depot· $169.00 USD
Crankshaft Harmonic Damper (240Z/260Z/280Z/280ZX) ↗Z-Services· €215.00 EUR
Euro Harmonic Damper, 70-83 240Z, 260Z, 280Z, 280ZX ↗Motorsport Auto (The Z Store)· $199.95

Fuel & Ignition 1

Electric fuel pump
Wired in to replace mechanical fuel delivery
In the shops
Electric Fuel Pump and Filter Combo - 280Z/280ZX EFI ↗Z Car Depot· $239.00 USD

Cooling 1

Aluminum radiator
Purchased as replacement radiator during header install
In the shops
Radiator Hose Aluminum Tubing (1.25", 240Z/260Z/280Z) ↗Z Car Depot· $15.99 USD
NC Aluminum Race Radiator ↗Flyin' Miata· $549.00 USD
Single Pass Aluminum Race Radiator (ND) ↗Flyin' Miata· $549.00 USD

Gearbox & Drivetrain 1

Subaru R180 differential with limited slip
Installed as the rear axle with LSD
In the shops
Stub Axle Set for Subaru R180 Differential Conversion ↗JDM Car Parts· $498.00 USD
Rear Limited Slip Differential ↗Motomobil· €563.00 EUR
R180 Rear Differential Cover Gasket ↗Z Car Depot· $9.99 USD

Suspension & Steering 2

BC Racing coilovers
Installed as suspension upgrade
In the shops
Tein Super Racing Coilovers ↗JDMuscle — Mazda MX-5· $3,126.00 USD
BC Racing Honda Integra/RSX DC-5 Coilovers ↗Paramount Performance· $1,122.18 USD
BC Racing Coilovers - Suzuki Solio (1999-2010) ↗Paramount Performance· $1,068.17 USD
Polyurethane suspension bushings
Fitted throughout suspension
In the shops
Suspension Kit, Poly Bushings ↗Moss Motors – Triumph TR6/TR250· $252.47 USD
Shock Bushing Set (Polyurethane) ↗bpnorthwest.com· $8.99 USD
Polyurethane Panhard Rod Bushing Set ↗Moss Motors – Triumph TR6/TR250· $15.99 USD

Brakes 1

Rear brake components
Machined rotors, new shoes and cylinders fitted on rear brakes

Body & Trim 2

240Z taillight panels
Used set sourced and fitted in place of 260Z panels
In the shops
Rocker Panel Hole Plug (240Z/260Z/280Z) ↗Z Car Depot· $1.89 USD
Rear Taillight Panel, Steel ↗Chicago Muscle Car Parts - 1969 Camaro· $139.00 USD
Taillight Panel - 1969 Camaro ↗Auto Metal Direct - 1967-69 Camaro· $184.99 USD
240Z bumpers
Fitted to the car in place of stock 260Z bumpers
In the shops
Rear Hatch Bumper Stop and Dovetail Screw (240Z/260Z/280Z) ↗Z Car Depot· $1.19 USD

Interior 1

RSX seat
Sourced as a replacement seat, noted as not an exact match to the other

Electrical 5

280ZX non-turbo distributor
Fitted to replace original ball-bearing distributor setup
In the shops
Factory Camshaft Performance Regrind, 70-83 240Z/260Z/280Z/280ZX Non-Turbo ↗Motorsport Auto (The Z Store)· $339.87
Factory Camshaft Performance Regrind, 70-83 240Z/260Z/280Z/280ZX Non-Turbo ↗Motorsport Auto (The Z Store)· $339.87
Factory Camshaft Performance Regrind, 240Z-260Z-280Z-280ZX Non-Turbo ↗Motorsport Auto (The Z Store)· $339.87
Alternator from 1999 Nissan Pathfinder
Internally regulated alternator fitted to fix electrical shut-off fault
New ignition switch
Replaced while diagnosing random shut-off issue
Megasquirt ECU
Standalone engine management installed and tuned, with RPM signal fault traced to a resistor
AEM wideband sensor
Fitted for tuning, fixed by grounding a wire
In the shops
AEM X-Series Wideband Gauge Kit ↗Flyin' Miata· $259.00 USD
NGK Direct-Fit Wideband Air/Fuel Ratio Sensor (92-00 Civic) ↗JDMuscle — Mazda MX-5· $339.00 USD

Photos

90 pictures collected from the write-up, in the order they were posted, shown from Early 1974 260z build (HybridZ). A picture opens larger here, with the way through to the page it is on.

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How it was done

Starting condition

The car arrived as an early pre-August 1974 260Z, sold as running but actually suffering a fuel delivery problem. It had its original L28/N24 engine, round-top carbs, factory AC, and a 5-speed swap of uncertain condition. Rust was limited to the driver door, with a dent near the rear taillight.

Fuel system and early running issues

The owner cleaned the tank, replaced brittle fuel lines, fitted a new sending unit and electric pump, and rebuilt the carbs. Getting the engine to idle and rev properly took months of troubleshooting wiring, vacuum leaks, and carb float settings.

Head failure and replacement

A hydrolocked cylinder led to the discovery of a cracked exhaust valve. A used N47 head was sourced and fitted, with new gaskets, head bolts, and valve lash set. The car was eventually got running again, though further issues followed.

Chassis and interior refresh

Over subsequent months the owner installed BC coilovers, a Subaru R180 LSD rear end, polyurethane bushings, new wheels and tyres, rebuilt rear brakes, sound deadening, and new carpet, alongside electrical repairs.

Turbo and Megasquirt conversion

The project shifted toward forced induction: a turbo manifold was cleaned, wrapped and fitted, oil feed and drain lines added, a P90A head sourced and machined after warping, and the engine converted to Megasquirt standalone control. After sorting ECU wiring faults the car was finally driven.

Progress so far

Later posts cover fixing a random shut-off fault with a new ignition switch and alternator, fitting 240Z taillight panels and bumpers, trying different seats, and finally weighing the finished car at 2680 lbs. The build remains an ongoing project.

A summary in our own words. The full account, with all its detail, is in the original write-up: read it at Early 1974 260z build (HybridZ) ↗

Worth knowing

Changing many engine variables at once (timing, carbs, vacuum, plugs) at the same time makes diagnosing a no-start much harder
A cheap aftermarket harmonic balancer's timing marks can be inaccurate, so verify TDC independently
Megasquirt rising/falling edge trigger settings can cause rev limiting and sync losses if set wrong