MG Midget

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How to tune and improve your Austin-Healey Sprite or MG

Spridgets are good cheap fun and many reckon that they perform better than the larger MGB – certainly the handling is more kart-like which makes them ideally suited for track work and autotesting. There’s masses you can do to make a Midget (or the identical Sprite of course) walk tall and unlike the original Frogeye, there’s so many around that you don’t have to be worried about originality. Also there’s the benefit of brand new bodies available off the shelf from BMH.

BEFORE YOU START...

Rust is the main worry with any Spridget and the majority have been patched up over the years because the monocoque construction corrodes very badly. Worst areas are the rear spring mounting boxes located behind the seats and if really bad consider another shell because you’ll never bring one back from the dead cost effectively. Other areas to watch include the sills and A-posts. Wheelarches and lower rear wings rust badly, too as does the boot, bonnet etc As a plus there are one-peice fi breglass front ends which rid the rust and also save weight.
In complete contrast, you can sleep easy about the oily bits, which are both durable, easy to fi x and inexpensive – there’s a lot of Minor and Austin A35 in the car’s make up remember. A bog standard Spridget is a rare thing as these cars were tuned and modified to the hilt when contemporary and for these reasons there’s a high number of uprated cars on sale which may be the best starting point. Best of all there’s a fair smattering of period tuning parts to be found via clubs and autojumbles from established tuners such as Speedwell, Downton, Oselli and even BLST (British Leyland Special Tuning).

HOTTING UP

This feature deals primarily with A-Series-powered cars as the Triumph 1500 engine isn’t as tunable, has weak bearings plus overheating characteristics although the fundamentals are similar.

The 1098cc engine which powered Spridgets up to the mid ‘60s is a sweet good revving engine but the larger 1275cc unit is lustier and has more tuning potential, especially the cylinder head, plus are more freely available. If possible look for one stamped 12CC as it’s almost to Cooper S spec before you even start tuning.
How far you want to tune the engine is up to you but 135bhp from a 1380cc (where 1.3 Triumph Spitfi re used to be fi tted in the ‘70s!) A-Series is not unknown albeit too racey for road use. But certainly a nice 1275 unit, bored out by 0.020in to 1293cc and just duck into ‘Under 1300’ motorsport categories, can make a mighty Midget or a sprightly Sprite.

Basic mods should start with a good decoke and a set of free-flow air filters from the likes of Pipercross or K&N. Together with the engine set up on a rolling road (perhaps with altered carb needles and springs) will yield another five bhp – more if you add an LCB long centre branch exhaust manifold.

A modifi ed cylinder head is next with better porting and larger valves before fitting a sportier camshaft although you’ll lose some of the lovely low speed torque this engine is famed or once you do this so consult an A-Series expert for advice. A lively 75bhp is easy and may prove ample. ‘Stage Three’ with an almost racing-spec head, even better cam and re-jetting of the carbs – perhaps looking at a single 45 DCOE Weber – sees 100bhp. A better ignition, such as an electronic set up from Aldon, Lumenition or a 123 pre-programmed distributor plus Duplex timing gear, is pretty essential.

BUDGET

• Sports air filters
• New carb needles and springs
• Rolling road tune up, decoke
• Better exhaust system
• Electronic ignition, distributor

FULL THROTTLE

• Supercharging
• 1293/1380cc bore engine
• Head and camshaft changes
• K-Series engine transplant
• Ford Type 9 transmission

TURN KEY TUNING

With camshafts costing around £85 and cylinder heads around £400 it may be more prudent opt for a fully reworked engine which can work out the most cost effective route, especially if yours is in need of an overhaul; don’t waste money tuning a tired engine. For example, Oselli sells a Stage Two 1293cc exchange unit for a reasonable £1800 touch. Moss and the MGOC have similar offerings, so shop around.

Supercharging used to be popular back in the 1960s and a complete kit is available but costs the thick end of three grand! The way to go for real performance now is to fi t a K-Series engine. Frontline Developments (www.frontlinedevelopments.com) makes a full and nut and bolt kit that means you don’t need butcher the car about but costs over £2100 sans engine (although these can be picked up extremely cheaply). To be fair, individual parts, such as bell-housing, fuel take off, coolant rail and engine mounts can be bought individually.

If doing it yourself, the heater tray needs modifying as does the radiator but you’re going to have a quick car although for ease of fitting, a pre-‘94 Rover 200 or Metro engine is better suited as it uses a simpler engine management system.

Incidentally, back in the 1970s a company called Car Preparations produced a Cortina GT-powered Midget called Atlantis which performed well. Save for mods to the bulkhead, transmission tunnel, propshaft, engine mounts, clutch it’s a fairly uncomplicated swap and gave a 0-60 skit in 10 seconds but these old Ford Kent engines are becoming pretty pricey to buy.

So to the 1500… The enlarged 1296cc unit isn’t half as rev-happy or sweet as the 1.3 but around 100bhp is still attainable. A Stage 2 engine from Oselli, MGOC and Moss retails at a little over £2000.
More power means a better gearbox and the celebrated Ford Type 9 fi ve-speed conversion is great, boasting better ratios as well as longer legs for the considerable £1600 outlay. Go for the kit from experts Frontline Developments and a special gearbox casing means the gear lever fi ts exactly. Finally, boy racer antics – or perhaps autotesting – can snap driveshafts but Frontline sells uprated types for £140 or so to cope with this.