Rootes 1725 OHV I4 (Peykan) – Classic Iranian Carbureted Engine

Rootes 1725 OHV I4 (Peykan) – Classic Iranian Carbureted Engine
by DanielcoderX

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A realistic recreation of the legendary 1.7L Rootes 1725 inline-4, as used in the iconic Peykan — originally derived from the British Hillman Hunter platform.

This is a naturally aspirated, carbureted, pushrod (OHV) engine tuned to reflect the stock daily-driver character: smooth idle, strong low-end torque, modest top-end power, and heavy rotating assembly feel.

⚙️ Engine Specifications

Configuration: Inline 4
Displacement: 1725 cc
Bore x Stroke: 80.26 mm × 86.00 mm
Valvetrain: OHV, 2 valves per cylinder
Compression Ratio: ~8.8:1
Redline: 5500 RPM
Firing Order: 1-3-4-2
Fuel System: Single carburetor
Ignition: Mechanical distributor with advance curve

🔧 Simulation Details

This model includes:

Realistic port flow data based on small-port OHV head characteristics
Mild stock camshaft (≈206°/203° @ 0.050", ~9mm lift)
Heavy crankshaft + flywheel mass to reflect authentic throttle response
Carbureted intake behavior with soft throttle mapping
Period-correct ignition timing curve (max ~34° advance)
Stock 4-speed manual gearbox
Vehicle model approximating Peykan weight and aerodynamics

The engine delivers:

Strong low-end and midrange torque
Limited high-RPM breathing (long-stroke undersquare design)
Stable idle and smooth cruising characteristics
Authentic vintage carburetor sound character

🚗 Driving Character

Expect:

Lazy but torquey acceleration
Noticeable flywheel inertia
Early torque peak
No high-RPM screaming — this is not a race engine

It behaves like a durable 1960s–1970s economy sedan engine — simple, reliable, and mechanically honest.

main.mr

import "engine_sim.mr"
import "themes/default.mr"
import "engines/danielcoderx/peykan.mr"

use_default_theme()

set_engine(peykan_rootes_1725_i4())