The Tuning Guide
Tuning the Triumph Stag: the complete guide
Tuning a classic V8 sounds like a dark art. It isn’t. Strip away the mystique and it is two jobs, getting the spark right, and getting the fuel right, done in the right order, with an understanding of what each part is actually doing. This guide explains all of it from first principles, with the specifics of the Stag’s twin Zenith‑Stromberg carburettors throughout. Read it start to finish, or dip into the part you need.
By Jon Cosson. The guide is being built out chapter by chapter; the sections below are those already written, with the ignition-side and the Stromberg set-up pages to follow.
Start here
The ignition side
How a distributor works
Points, condenser, cap and rotor, and the centrifugal and vacuum advance, how the Stag's twin-point Lucas distributor triggers and delivers the spark.
Ignition timing explained
What timing means, why the spark fires before top dead centre, advance, and how the Stag is set, including its quirk of timing from cylinder two.
Spark plugs, coil & firing order
The coil and ballast, HT leads, reading spark plugs, and the V8's unusual 1-8-4-3-6-5-7-2 firing order and cylinder numbering.
The fuel side
How a carburettor works
The venturi, the two families of carburettor, and exactly how the Stag's Zenith-Stromberg does its job, in plain English.
Setting up the twin Strombergs
A fixed sequence, diaphragms first: float level, the air valve and needle, balancing the pair, mixture by the needle adjuster, and the exhaust-analyser check.
Reference
The specialist
With thanks to AG Classic Car Tuning
This guide is illustrated with thanks to Andrew at AG Classic Car Tuning, a North Yorkshire mobile specialist in the carburettor‑and‑distributor classics of the 1930s to 1990s, SU, Stromberg, Weber and Solex, who tunes these cars for a living.
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