Owners know how to make their MGBs and Midgets faster and handle better – or do they? We delve through the archives to see what the experts thought of the mods when new

Followers of our Road & Track articles will know they are geared to give the best current advice on how to modify popular classics for fast road and mild competition use. On many classics, the recommendations given by experts have remained largely unchanged over the decades, while on others, continued refinement has led to new improvements being devised and even new ways of thinking. In the case of the MGB and its smaller brother Midget, it’s a bit of both.

While we can pass on the advice from top experts, it’s nice to be able to back up these top tips with proven facts on the worthiness of some mods – after all, what one driver may prefer, the other may not!

In this special Road & Track we’ve been able to delve through a wide collection of major authoritative road tests and driving impressions of tuned MGs when they were contemporary, to give an insight of the effectiveness of certain modifications and to give you a guide of what to expect.

It’s natural to expect improvements and refinements brought by today’s tuning equipment so bear this in mind, too.

MIDGET/SPRITE

The fundamentals of tuning the evergreen A-Series engine haven’t changed much over the decades. The limiting factor of the unit lies in its non cross-flow cylinder head design featuring Siamese porting, although this has never stopped respectable power outputs being realised. The standard spec camshafts employed are of a quite racy design and in 65bhp 1275cc form, the engine is close to Cooper S tune that’s easily improved further with better air cleaners and manifolds, especially the restrictive exhaust, before going to town.

Speak to experts such as Robin Lackford Engineering http://www.robinlackford.co.uk who not only specialises in Midgets and Sprites but also sponsors the very popular racing challenge for these cars.

Ex Hot Car and Cars & Car Conversions editor and now regular writer to Classic Motoring Paul Davies remembers such period tweaks well. “With the A Series, the easiest bolt-on is to replace the twin 1¼ in SUs with a pair of 1½ in units, making sure the inlet manifold is suitably matched, of course. Beyond this, you can substitute a single dual choke Weber with 40mm chokes, although I must add that when I tried this back in late ‘60s, the engine was devil to start and, even with standard camshaft, there was a great big hole in the power band!

“But there’s not much point changing increasing the fuel mixture entering the cylinders and improving the combustion if you don’t look to more efficient means of swiftly and efficiently extracting the exhaust gases. Back in those good ’ole days, BL Special Tuning dabbled with both twin Webers and four Amal motorcycle carbs.

Again, I tried the Amal route (on a rally Marina), but it was over-complicated and a pair of large SUs proved almost as effective for road/rally use. Nowadays, motorcyclecarbs seem to be the way to get ultimate power on A-Series engines.

“I had a ‘531’ works-profile cam along with modified head and standard carbs on one Spridget that I owned, and it seemed quite effective although it meant that you needed to rev the little engine to get on the power band.”

The 1960s and ’70s were wonderful times for boy racing with an army of independent tuners plus factory ‘works’ divisions such as British Leyland Special Tuning (BLST) who devised most of the tuning gear for the A-Series anyway such as eight port cylinder heads, fuel injection – it was all available if you had the money! But sometimes less is more, especially if you need the car for normal road use.

When Davies tried BLST’s road going racer, boasting almost everything available for the A-Series (including a special, crank, flywheel and dished pistons), a virtual 100bhp from its hybrid 1293cc engine (and at £200 a hefty sum back in 1970) was just about tolerable on the road although with a 7800rpm rev limit, and an idling speed of 1500rpm, it was only for the die-hards.

“Below 3000rpm it just coughs and splutters”, he wrote adding real power didn’t come until 5000rpm; 0-80mph came up in 19.4 seconds which was almost half the time of a standard Midget.

Two years later Motor magazine got its hands on a tamer ‘Stage 2’ Midget, again from BLST, and while power was probably 20-25bhp down it was almost as quick on the road. The term Stage 2 meant essentially the ‘top half’ of the above engine (with twin 1.5in SU carbs) but the ‘bottom end’ was standard, including the camshaft. Yet, from a standing start, the 10 second sprint to 60 was almost identical – the gains came after that. However, as compensation the ‘Milder Midget’s’ ‘in gear’ acceleration times, (thanks to retaining a standard camshaft) trounced the ‘full race’ car all the way until the 70-90mph top gear spurt when the racer got its nose ahead.

The Stage 2 was always usefully quicker than the standard car throughout the ranges which is not always the case with tuned engines, especially high revving small capacity ones.

What we are saying is that you need to decide what you want from your engine; the racier you make it, the more you need to drive it. Today, with electronic ignition and more refinements to the tuning parts, we’d expect even better gains and it’s worth noting that despite having some 25 per cent extra power over the standard model, BLST’s ‘Milder (yet still mighty) Midget’ boasted significantly improved fuel economy – a win-win situation in other words.
MGB

Much the same applies to the big brother MGB with its not dissimilar B-Series engine although it can respond better to a camshaft upgrade without spoiling the pulling torque that this engine is famed for. Again, better breathing is the first step to make the most of what there is already care of modern air filters and a sports exhaust, plus manifold if funds allow.

Today, you can even buy alloy and cross-flow cylinder heads for the B-Series to make it surprisingly modern although for a similar outlay you can opt for a new, larger 2-litre B-Series engine, starting at just under £2000 from the MGOC, or £2250 for an even lustier 2.1 alternative, that can also be had in Stage 2 tune (£3495). All these units have been specially developed by the MG Owners’ Club and good value because when you consider that the club sells its Stage 2 cylinder heads at over £700 alone, with camshafts around half this, a complete tried and tested new complete engine is worth shelling out a bit more for.

If you have deep enough pockets you can go for Weber DCOE carbs and even fuel injection with modern engine mapping. At the other end of the scale (see new pages), back in 1973, Hot Car carried out a budget Stage 1 gas flowing of the standard head, which, along with less restrictive air filters, yielded 10bhp extra at the wheels – a useful gain for a few quid.

The same magazine tried a 140bhp engine fed by twin 2in SUs, admittedly in a Marina! It said that despite its full race cam “pulled from 2750rpm and went easily up to the 7000rpm redline” although economy really suffered at less than 20mpg!

Eye opening fuel drinking also fell to Motor when it tested a BLST Stage 3 MGB GT estimated at 112bhp. But here, unlike the A-Series, a racier camshaft didn’t upset low speed lustiness quite so much. True, at town and urban speeds in both third and top gears (including overdrive ratios), the standard engine posted slightly superior acceleration times but from 50mph the Stage 3 tune pulled away quite handsomely to the tune of four seconds in the critical 70-90mph overtaking increment.

Strangely however, third gear acceleration times were even-stevens when you would have expected the tuned unit, with its hairier camshaft, to be getting in its stride. Yet for all that the conversion was deemed a complete success. “The Stage 3 MGB is a great long distance cruiser which we thoroughly recommend”.

Economy, when driven hard, greatly suffered, at 17.9mpg, some 10mpg less than the standard car and it’s interesting to note that an MGBGT V8 is usefully quicker all round and much more economical!

A test of the MGOC 2.1-litre Stage 2 engine by a motoring magazine in 2006 concluded that it was now just about the “sensible extreme you can go for a fast road B-Series… giving a notable difference to the power and torque reserves”. It further added that the unit pulls cleanly and revs all the way to 6000rpm – sounds like the ideal MGB engine to us then!