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How to tune your MGB

Putting the sting back into your MGB Published: 18th May 2011 - 0 Comments - Be the first, contribute now!

How to tune your MGB
How to tune your MGB Crude but later R V8 front assembly transforms car and has better brakes
How to tune your MGB Uprated anti roll bars make a big difference to make car feel sharper
How to tune your MGB Telescopic damper swap is worthwhile but only if rest of gear is in good order
How to tune your MGB Rear springs settle badly with age. If replacing consider the R V8 ones
How to tune your MGB Supercharger (from Moss Europe) kit pulls out big power and is straightforward fit but will put a lot of strain on a worn engine
How to tune your MGB Sticking with original lump? Then a gas flowed bigger valve head with rejetted carbs and a sports exhaust is the best value in terms of bhp
How to tune your MGB The B Series is tough and tunable – just don’t sacrifice all that lorry load of torque. You can also buy bored out units but the best swap is still the classic Rover V8
How to tune your MGB Unless is knackered don’t junk O/D in favour of a five-speed conversion. Later switch is safer and more usable
How to tune your MGB Drilled and Grooved discs from Moss Europe
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MG expert David Knowles shows the best way to tune and improve your MGB for modern roads but without losing its essential classic character

The MGB may be the most popular classic sports car ever made, but for some people that only serves to reinforce the notion that familiarity breeds contempt. Critics said the MGB was old fashioned when it was launched over 40 years ago. That’s another argument, but you have to admit that while the MGB may have been be okay on the roads of that time, the levels of performance that a standard specimen musters have fallen some waybehind today’s expectations and needs. This article sets out to explore some of the more practical ways to redress the balance.

Standard bearer

The first lesson to learn in improving the performance of an MGB (or even a Ferrari for that matter) is to ensure that the fundamentals are absolutely right before splashing out on any tempting modifications. It is all very well dreaming about making your trusty steed a road burner, but first it would be wise to invest some money in making the car as good as it should be before you embark on any further mods. A thorough service and tune up (perhaps with a session on a rolling road to play around with better carb and ignition settings), paying special attention to the state of the suspension, steering and wheel alignment (plus a decent set of good quality tyres) can transform any old jalopy. Similarly, no fancy mods can ever be a substitute for clapped out mechanicals. So before you shell out your hard earned cash, first make sure that your MGB is up to scratch.

Cool head for a hot car

First important step is to plan sensibly ahead and budget accordingly – and try – if you can – to avoid buying on impulse or doing things out of order. If you haven’t done so already, arm yourself with a good set of manuals. The factory parts and workshop manual relevant for the year of your car are good starting points – while the Haynes manual is a sensible backstop. Next, obtain the very useful catalogues available from leading MG specialists, and set aside a few evenings to plan your campaign in greater detail. Make sure that the basic structure of the car is sound. It might seem obvious that the car should be solid and free of the dreaded tin-worm, but I have seen all too many up-rated death-traps where the first investments have not been the most sensible. If you want to make serious improvements to the performance of your MGB which, by their nature, will impose much greater stresses and strains on the structure ofthe car, then it may be well worth considering a new Heritage bodyshell. Extravgence? Well, it is not a cheap optioncertainly, but remember that the MGB is one of only a handful of classic cars for which a brandnew factory-tooled bodyshell is readily available.

The standard MGB wheels and tyres are typically fourteen inch diameter on weedy 4.5 or five inch wide rims with slimline 165SR 14 rubber, but the latter are nowadays usually superseded by the relatively more commonplace 185/70 HR14 size, which has the same rolling radius and therefore gives no problems with overall gearing and minimal risk of fouling of the wheelarches. Even though many moderns come with gumball like superglue tyres this size is still ample enough for the B. You can substitute the standard wheels with attractive alloys – arguably the best style for the MGB being the various ‘Minilite’ style eightspoke wheels, which are available in both conventional four-stud and centre-lock variants to suit. Don’t be tempted to go for anything much more exotic – the chances are that it won’t fit, and in any case will do nothing for overall performance. MOSS offers a fifteen-inch diameter alloy wheel and having run a day-to-day MGB for five years on a set of these, I can testify they offer no problems. If you must go for more exotic wheel and tyre combinations, be warned that there is a strong risk of wheel-arch fouling – particularly at the rear – unless you go for a set of sexy ‘Sebring’ style wheelarch extensions modelled on the ones sported by the exotic MGC GTS. Tyre choice is critical yet something skimped by many enthusiasts. Don’t penny-pinch here – they are your only contact with the road.

Engine & Transmission


Having got the basics right, now is the time to turn your attention to achieving greater performance in terms of speed and acceleration. Although rugged that old B Series lump is as rough as old Harry. Thankfully MG benefits from the terrific legacy of ‘Special Tuning’ that was practiced at the badge’sspiritual Abingdon home, and before considering any exotic mods that are nowadays on offer,it is worthwhile taking a look at the basics first. Firstly is the engine up to any power hikes? Sadly the answer in all too many cases is that unless it has received much TLC over the years the unit may not stand any meddling and tuning with! So if you are in the slightest doubt consider overhauling the lump as the first step to more pep. With the demise from high-street forecourts of both four-star and LRP, there is a strong temptation to consider the fitment of a new ‘unleaded’ cylinder head, with the hardened valve seat inserts that can cope with the sad loss of tetra-ethyl lead or substitutes. However, most specialists seem to reckon that while this is achievable, on an older worn engine it is simply a false economy not to simple replace the whole engine with a properly reconditioned unit at the same time. It is a great truism that there is ‘no substitute for cubic inches’, and the MGB is no exception. What that old B-Series lacked in bhp it made up for it in torque, which has far more relevance in real world motoring.In place of the standard 1798 cc, it is perfectly feasible to upgrade to an 1850, 2.0-litre or even 2.1-litre units. However, to make the most of the more expensive larger-capacity units, you really need to invest yet more money in better carburation and a free-flowing exhaust. Most of the leading MG specialists offer a range of engines in various stages of completeness. A typical Stage 2 1860 c.c. from MOSS will be supplied with fully balanced flywheel, clutch and crankshaft, but its 2100 c.c. units also come with inlet manifold, carburettors and distributor. Prices typically range from £1870 for an 1860 Stage 2, through £3200 for a 1950 Stage 2 and up to £3160 for the top 2100cc versions. If you fancy the idea of supercharging, MOSS can also offer a kit which it maintains can be fitted over the course of a weekend by a competent home mechanic, and can yield a massive 40 per cent boost to engine output. The idea is very attractive, but do not prepare to waste your money – over £2000 of it – if your engine is not up to the extra stresses and strains. In the twilight production years of the MGB, plans were in place to replace that venerable engine with twin-SU and turbocharged versions of the much newer single-overhead-cam O-Series two-litre unit. These ideas came to nought, although work on the turbo’d O-Series was later put to use in the rapid Turbo versions of the Montego and Maestro.

Some years after that, when the engineering team first conceived the ‘reborn MGB’ that evolved into the MG RV8, the then current ‘EFI’ fuel-injected two-litre twin-cam T-16 Rover engine was considered, married to the ‘77mm’ five speed gearbox from the Rover SD1. However, although one or two enterprising individuals have built their own ‘EFI’ MGB conversions, such upgrades have always playe very much second-fiddle to the more popular V8 swap. Part of the problem is the packaging of the T16 in the MGB’s engine bay, for the greater bulk of the much larger cylinder head and ancillaries mean that there is a clash with the heater box for starters. For some fair-weather enthusiasts this may not be considered a problem, but for round year use an MGB without a heater is not a practical proposition! The ultimate conversion is always going to be the Rover V8 unit, and nowadays the options run from the original style 3.5-litre (although nowadays often fuel injected) up to the 4.6 unit as seen in second generation Range Rovers. The limit here is really only governed by the size of your wallet, so if funds are tight and you are sticking to the original engine then concentrate on that prehistoric cylinder head design. Just a simple stage one or two upgrade with rejetted SUs,ripping out emission equipment reaps considerable rewards, especially with a long centre branch exhaust, topped by electronic ignition and a session on the rolling road. Around 130bhp is perfectly attainable Hairer cams are freely available but don’t ruin the low-speed torque. ‘box of tricks The original four-speed transmission was always pretty marginal on the factory MGB GT V8, and anyone contemplating a V8 swap should look at using the later and much stronger Rover SD1 ‘77mm’ five-speeder. For a four-cylinder MGB with a moderate power upgrade, the transmission remains more than adequate, and to my mind at least, the overdrive remains part of the classic appeal of the car. MOSS’ up-rated overdrive unit with stronger springs and up-rated lining material for £405 is designed more for track use. If you must go for a fivespeed conversion (and with an overdrive there’s really no need to for most road uses) you can fit either an adapted Rover unit orthe ubiquitous Ford Sierra ‘box. However, for my money there are better things to spend your money on first. If you preserve with the o/d then consider changing it to the later gear knob mounted switch; having the gear lever on the left and the overdrive switch dash mounted to the right leaves you precious little time for that central steering wheel!

And Now it’s Your Turn…

I hope that this feature has given you food for thought and shown that for a reasonable well-planned outlay, an average MGB can be brought up to more modern standards of performance, and this includes the handling and braking. Not everything has to be done at once, but if you follow the logic of changing the basic things like suspension and brakes before you significantly uprate the power, then the end result should be a real fun car that’s safer and better to drive into the bargain. The MGB is one of the greatest classics on our roads. Subtle mods only makes this splendid car even better.


Mention tuning and most people think of pulling out extra horses from the engine. Don’t! In fact, proper sensible tuning starts elsewhere. As lowly as the bhp is on a standard B, it’s still fairly adequate for our gatso-infested roads. No, real speed comes from cornering quicker, safer. Fortunately such basic aspects of the MGB suspension as the geometry and standard components are a sound starting point. The designers of the B would have liked to have gone for a ‘modern’ coil-sprung suspension all round – maybe even an independent set-up at the rear but there wasn’t the funds. While there are some nice independent-rear-suspension conversions on offer from leading MG specialists, they are in truth more of an exotic curiosity than a must-have improvement. Conventional handling improvements can be wrought by investing in uprated anti-roll bars to counter the inherent lean. A front anti-roll bar from MOSS Europe will typically set you back anything between £30.95 for a standard unit up to around £135 for a special ‘fast road’ 7/8 incher. Don’t fit a rear anti-toll bar as it make the car too snappy. For everyday use the standard old-fashioned Armstrong lever-arm (below) dampers actually remain pretty effective still – provided that they are in good nick that is. And avoid some of the cheaper ‘reconditioned’ replacements though if you are sticking with this type of design. It is better to invest in the new ones available from companies like MOSS, Brown & Gammons and the MGOC Spares Shop. A popular conversion is to swap to conventional tubular shock absorbers – a cheaper proposition at the rear than at the front – where the lever arm unit doubles up as the upper part of the wishbone assembly. While these kits will provide improved long-term reliability and better standards of on-the-limit damping, don’t fall into the trap of believing that somehow they will deliver a vast improvement or, more specifically a firmer ride: stiffness and balance are much more a function of spring rates, coil length, bushes and suspension geometry. Speaking of bushes, the standard factory-spec two-part rubber bushes fitted to the front wishbones of all MGBs – bar the V8 version – are an absolute abomination, and if you are looking at improving the handling of your car these should be ditched at the earliest opportunityin favour of the single-part V8-type bushes made from either rubber or uprated polyurethane. Be prepared for a slightly harsher ride in thecase of the latter type, however but they are more positive. The MGB suspension set-up came in for a lot of review and clever redesign for the MG RV8 of 1992-1995; indeed, some of the development work was carried out by present-day MG Rover Engineering supremo RobOldaker and so for the ultimate in MGB suspension upgrades, you could do worse than look at themore modern single-leaf rear springs available from specialists. The key improvement on the RV8 however was to the front, and thanks to British Motor Heritage, a wide range of RV8- based kits are available that allow vastly improved front suspension to be simply bolted in place. The kits may seem quite a lot of money – they are typically between £2170 and £2510, dependent on the model and wheel type – but you should bear in mind that for your money you get not only a much more sophisticated and durable set-up, but a pair of four-pot callipers and vented discs also comes as part of the package. No drilling or major mods are needed, and so if you are later bitten by the concours bug, it is no problem to return the car to standard specification if you so desire. On later rubber bumper Bs before any mods are carried out the ride height must be lowered to earlier levels – and remove the rear anti-roll bar if fitted, unless you like snap oversteer. But Bs can be made to handle.

If you are going to make your MGB faster, it’s imperative that unless you propose to explore the contents of your local hedgerows, you will need to be sure that you can stop properly. The standard set up on the MGB is conventional, with slim unventilated discs up front and drum brakes at the back. There are some exotic kits available for upgrading to allround discs, but these are not really needed unless you are exploring the upper reaches of V8 power or the extremes of track-day eventing. If your budget can run to it, the MG RV8 type front suspension system referred to in the suspension section above is a neat and relatively simple bolt-in that kills several birds with one metaphorical stone; coil-over springs, better bushing, longer service life and vented disc brakes. On balance, I reckon that this kit is a really sound investment, but if your budget is a little tight, there are other more affordable ways to improve yourstopping power. The cheapest and traditional option is to go for harder brake pads, which will make some difference, but do have a look at the possibility of upgrading from the standard discs to the drilled or grooved discs which are available at a reasonable cost premium. As an example, MOSS offers drilled discs for a very reasonable £42.95, or you can go for grooved disc at £99.95. Anything more exotic will usually involve changing the whole disc and calliper set-up (MOSS do a four-pot calliper kit for £645), but it has to be said that before long the costs of these and other mods to the front suspension can so easily creep up towards the price of that RV8 front end! We take it of course that the standard anchors are in tip-top order. It’s surprising what a thorough check over with new pads, linings and brake fluid can yield.



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