1975 Austin Allegro 1.5L Petrol · JAE 739N

The SOHC E-series 1500 and 1750 engines borrowed from the Maxi are the Allegro's performance answer but its reliability question: Classic & Sports Car's buying guide states the E-series can be prone to head-gasket failure and tells buyers to check the cooling system for leaks or overheating, look for emulsion in the oil filler cap and oil in the coolant. Auto Express's club review similarly lists coolant and temperature vigilance as routine Allegro maintenance, and the head itself is an expensive skim-or-replace job once it has been overheated. The A-series 1100 and 1300 cars are less exposed and cheap to rebuild if they are worn, which is why the guides consistently recommend A-series condition over E-series pace unless the seller can prove the cooling work has been done.

Despite the joke that rust-proofing was the only thing BL got right on the Allegro, the marque reality is that sound bodyshells are the scarce resource: British Classic Cars' checklist names sills, floors, subframe mounts, inner wings and the base of the A-posts as the rot points, and warns structural repair sections are limited. Classic & Sports Car adds that supplies of new front wings are drying up so rusty wings need costly repair, and Auto Express records how BL dealers were issued a service bulletin showing where to drill holes in the boot floor to let water out — a factory admission of water ingress that still condemns many cars today. Condition before specification is the rule: pay for a dry shell and put up with the wrong trim rather than the reverse.

Hydragas was the Allegro's party piece — interconnected gas-and-fluid springing that gave a long-legged ride — and its age problem: the displacer units slowly lose their nitrogen charge, and there was no factory provision to replace the gas, with HAHS noting charges were only expected to last around 15 years. Their Hydragas service page describes cars crashing over bumps, diminished ride height, harshness when pumped up, and shortened displacer life from continued driving; used or NOS substitutes usually disappoint because they too have leaked gas. The good news: specialists in Telford regas all Hydragas units with a mobile fitment option, and Classic & Sports Car confirms sagging Allegro suspension can be pumped by any MGF-servicing garage provided the spheres are intact — bounce each corner, and if one is hard, budget for sphere or unit work.