Your motoring questions

“Matching numbers” means the serial numbers stamped into the chassis frame, engine block casting, and (where recorded by the manufacturer) the gearbox casing and body number tag match the original factory build sheet, Kardex card, or British Motor Industry Heritage Trust certificate. However, buyers and historians should remember that many racing cars swapped factory replacement engines in period during endurance seasons. Furthermore, a restamped block can mimic original font punches, so metallurgical grain inspection and font-depth verification remain essential.

Before Edward G. Budd’s all-steel stamping patents were adopted by high-volume manufacturers like Citroën and Dodge, building hardened steel dies for a run of fifty coachbuilt bodies was financially impossible. Seasoned European ash (Fraxinus excelsior) offered straight grain, resistance to splitting when screwed or pinned, and natural elasticity. Because pre-war ladder chassis flexed several millimeters over rutted roads, an ash framework allowed the body to move slightly without tearing the hand-formed aluminum skin.

Unmodified fuel systems from before 1990 face three distinct challenges with E10 (10% anhydrous ethanol): First, ethanol acts as a solvent that dissolves older nitrile rubber hoses, cork float coatings, and leather or rubber mechanical fuel pump diaphragms. Second, ethanol is hygroscopic, absorbing atmospheric moisture inside vented fuel tanks and causing phase separation and white zinc-oxide corrosion inside Mazak/Zamak carburetor float bowls. Third, ethanol contains less energy by volume than pure gasoline, slightly leaning out the air-fuel ratio. Replacing rubber components with SAE J30R9 fluoroelastomer hose and fitting brass floats solves the hardware issue.

Modern passenger cars use roller cam followers and low-phosphorus oils designed to protect catalytic converters. Classic overhead-valve and overhead-cam engines with flat tappets or inverted bucket followers rely on Zinc Dialkyldithiophosphate (ZDDP) at concentrations of 1,000 to 1,400 ppm to create a sacrificial microscopic anti-wear film under the extreme sliding pressure of the camshaft lobe nose.

Issued through national motorsport authorities on behalf of the FIA, the Historic Technical Passport is a detailed dossier—complete with photographs, casting dimensions, brake caliper specs, and homologation form references—confirming a historic racing or rally car complies with FIA Appendix K rules for its specific period classification (such as Period E, F, or G). It is mandatory for international historic events like the Le Mans Classic, Tour Auto, and FIA European Historic Rally Championship.

A surviving period chassis possesses a continuous chain of ownership and physical identity dating back to its original year of manufacture. A continuation car is built decades later by (or under license from) the original marque using unused serial numbers or original tooling. A recreation or toolroom copy is built by an independent specialist, often starting from a standard donor saloon or newly fabricated frame. Under FIVA standards, each category is legitimate only when openly badged and documented without misrepresenting its build date.

Patented by John Pugh of the Rudge-Whitworth Cycle Company in 1908, the splined hub and single central locking nut (“spinner”) allowed a racing mechanic with a copper or lead hammer to change a punctured tire in under thirty seconds—compared to several minutes for a five-lug wheel. In addition, the tensioned steel wire spokes promoted cooling airflow across hot drum and disc brakes while orienting the hub splines so rotational torque self-tightened the eared nuts on both sides of the car.

We welcome primary documentation—such as scanned period race programs, chassis plates, or workshop manuals—from owners and marque historians. Visit our Write In page to prepare a structured garage note for our editorial desk.