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MGB GT V8 Published: 7th Jul 2016 - 0 Comments - Be the first, contribute now!


Fast Facts

  • Best model: Original GT
  • Worst model: Bad home-made versions
  • Budget buy: Average examples
  • OK for unleaded?: Yes
  • Will it fit in the garage? (mm): L 6680mm x W 1656mm
  • Spares situation: Excellent
  • DIY ease?: Excellent
  • Club support: Typical MG
  • Appreciating asset?: Gap between a 1.8 is huge
  • Good buy or good-bye?: Former, and best MGB by far
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MGB, with more sting and Aston-like character. Officially only available as a GT but there are many DIY conversions around – some good, some bad. Price parity with MGB has gone however with values soaring of late

There’s no pleasing some, is there? Take MG lovers, who after years of crying out for a B with more sting, got what they had wanted and then decided they didn’t want it anyway!

“If ever one of our ‘Autoproject’ type of proposed designs were to come true, we hope it turns out as well as the Costello MGB V8…We can think of no reason why BLMC are not producing it themselves,” so said Autocar.

We’re talking about the MGB GT V8, the car that took a privateer to develop and literally forced British Leyland to follow suit. A much better car than the MGC, thanks to its lighter, more powerful Rover V8 as opposed to that anvil of a slogging straight six, and yet the heavily criticised MGC comprehensively outsold it, despite being in production for a year less.

There’s many reasons why MG missed the mark with its own V8, not least that it arrived on the market just months before the Energy Crisis of 1973/74, but for decades, they cost little more than a regular MGB GT to buy, and run. Happy days… because a top BGT V8 can make the thick end of £30,000, perhaps three times that of the 1.8!

Expensive on the face of it, but a bargain if you view the V8 as a scaled down Aston as many did in its day.

Bargains are now few and far between but you can pick one up for a little over ten grand to make good at your leisure, which is easy thanks to the usual excellent spares and support that goes with the MG badge. Fancy a Queen B?


1971 Abingdon had been developing an MGB V8 since 1967 (but officially since 1971) and first tried that wonderful Daimler V8 unit before opting for the logical in-house Rover unit. But it was Mini racer, the late Ken Costello, who showed the factory the way and who continued to make his own conversions even after the factory cars were launched.

1973 Unlike the full fat 160bhp Costello conversion, MG fitted the lower tune Range Rover-spec V8 (137bhp), allied to an MGC gearbox but with special closer ratios not used on Costellos and overdrive active only in top. The MGB GT shell, which demanded minimal changes to house the lighter V8 further benefited by altering the weight distribution from 47.8/52.2 to a more equal 49.4/50.6.
Suspension changes were only an increased ride height, pre-empting what BLMC had to do to the MGB a year later, and ‘Police’ spec rear leaf springs.

1975 The V8 received the infamous rubber bumpers, despite the fact that the car was never exported to the USA! No attempt was made to make a Roadster, as MG said the shell was not up to it. Costello always disagreed and was still making cars to order despite BL cutting off his engine supply immediately after launching its own effort!

1976 After the disastrous six-cylinder MGC, BLMC hoped that by giving MG fans what they cried out for it would sell like hot cakes, yet the MGB GT V8 was also given a lukewarm reception and pensioned off in 1976 after just 2591 cars were made, that’s about a quarter of what the MGC achieved. However, survival rate is brilliant says the MG V8 register, with some 1900 around.

1992 The car that MGB lovers always yearned for was finally produced – the RV8 roadster – but it was 20 years too late and the car was only a limited run.

Driving and press comments

Like the MGC, the BGT V8 was a tasty recipe but ultimately spoiled by being half baked and all the car did (and it has to be said that the official car was better developed than the Costello) was to highlight the shortcomings of the ageing MGB. It’s quite a different story 43 years on, where that ‘vintage’ Aston DB-like feel is now a positive asset.

Despite the ‘commercial’ two-star tune of the V8, performance was never an issue and a good one will still show many moderns a clean pair of rear tyres, (0-60mph in 7.7 seconds and 125mph according to Motor) and such is the torque on tap there’s little need for gear changing – a bit like a Jag. The standard overdrive gives a lovely long legged 28.5mph/1000rpm gait – strangely there was no automatic option, unlike the MGC.

When Autocar tested a Costello, performance was virtually identical despite its added 13bhp, which showed itself by a slightly higher top speed of just a shade under 130mph despite being slightly lower geared than the factory effort; in gear acceleration was pretty similar and it takes a good modern to still keep up with this old stager let alone trounce it.

Improved weight distribution, even against the normal MGB let alone the MGC, means that the bigger engine didn’t hurt the handling like it did before. That said, the V8 still didn’t handle quite as predictably as the four-cylinder MGB and road tests at the time put this down to the stiff rear suspension and added ride height, although there’s no shortage of improvements you can dial in to make yours handle to your taste. Other well known MGB traits such as the hard ride (always worse on a V8 than the MGB), wind noise (which one road test said made fast cruising “a misery”), poor heating and ventilation and lack of overall refinement are now of less hindrance than when the car was new and up against more modern designs.
“Telling BL what they ought to do has become a national pastime”, adding that “initial reaction to the car was quite enthusiastic, said Motor in 1973”, plus you have to bear in mind that hotted up MGBs, some with home-made V8s, were quite common by late 1973.

“So appealing is the BV8 package”, Motor continued “that, when the failings start to show themselves, there is a sense of disappointment.” but concluded that, “As a poor man’s Aston Martin V8 the new MG has a charm and, with improvements, could even be a worthy alternative”.

Rival weekly Autocar thought the handling not as good as the MGB, criticised the car’s general aged design, illogical high price (about the same as a Scimitar GTE) and signed off by saying that if the car did succeed in the showrooms, “It will be mainly due to the excellent Rover V8 for which praise cannot be too high”.

Autocar tested a Costello in 1972 and said, “As a conversion we rate this car as perfect and as a model in its own right deserves the highest of praise”, and its interesting to note that both Ken’s conversion and the cheaper factory car were priced just £100 apart.

However, a Motor tester at the time, the well known Porsche, Le Mans racer and 1978 Saloon Car Champion (works Dolomite Sprint) Tony Dron recently wrote a retrospective look at Ken Costello’s creation which he said was “seriously under-engineered” although went on to say that the performance made an ordinary B “look silly and even make mincemeat of the poor old MGC” but Dron reckoned that the only good V8-powered MGB was the later RV8. Hmmm…

Ken Costello, who died in 2015, beat BL once again when he was the first to get a TR7 V8 into production!

Values and the marketplace

BGT values are pretty much on par with the reborn MGC GT which means £25,000 for one of the best of the 1900 left. However, you do frequently see them sell for considerably less, so shop around, and £10-£12,000 should net a fairly nice example. The reason that V8 values have took off in a major way, believes Nigel Guild of Oxford-based Former Glory, is due to their comparative rarity and so few coming on the market plus recent positive press exposure, although Nigel feels some of the prices being asked at the top end are a bit too optimistic.

At the time of writing, Guild had genuine Costello (recently sold-ed) plus a pair of bespoke V8 Roadsters built upon Heritage shells but he rates the factory car the best developed and adds that he certainly wouldn’t touch a typical homemade V8 conversion because most are so poorly done.


Despite almost half a century on, a standard V8 is quick enough to hold its own against many moderns, so, for many, the car just requires some chassis tweaking. Lever arm dampers were still fitted front and rear, and so a swap to telescopics works well although the ride will be even harder and harsher. To really sharpen up the handling it’s worth fitting uprated front and rear anti-roll bars with poly bushes, although again the car will be made a lot harsher.

Servo-assisted brakes were fitted from the outset and this essentially standard MGB set up copes, although uprated EBC pads and better discs are always a wise move for modern motoring.

Alternatively, you can fit the more exotic MGR V8 front suspension and better brakes, which is expensive but an effective mod, as is MGOC’s even better Evolution3 front axle assembly.

Even if you keep the engine standard, a modern electronic ignition and an uprated radiator are very worthy mods, the former really helping the running says the V8 Register. As the basic V8 engine evolved into 4.6-litres over the years, in terms of power the sky’s almost the limit.

A stronger Rover SD1 five-speed can also be fitted; MGOC sells a complete nut and bolt kit to do this at some £2000 although with prices for really specimen V8s soaring, originality could be a key factor over the years – and besides, it’s nice to retain some of that Aston-like character!

What To Look For



  • The MGB’s simple suspension set up coped pretty well with the lighter if faster V8 power and doesn’t generally give more problems over any MGB. Kingpins - unless they’re greased every 3000 miles – wear out with ease, and so it’s a common MGB watch point.

  • The front wishbone bushes perish and collapse, but a visual check is all that’s needed to see what state they’re in. Always ensure that proper uprated V8 ones have been used over the standard MGB sort or perhaps a poly alternative has already been fitted?

  • Steering is characteristically heavy but should be pretty precise with it and with no wandering or excessive slack. There’s a power steering conversion kit offered by the MGOC but somewhat easier and much cheaper are aftermarket castor reduction kits which will lighten up the standard set-up.

  • If it seems that there’s excessive rear wheel steering on a test drive it’s likely to be the U-bolts and rubber bushes that locate the rear axle, have come loose or corroded.

  • Lever arm dampers were retained front and rear and are notorious for leaking. If you’re not worried about originality it’s possible to swap to telescopics. See that the car sits level and make sure that all the rear tyre is visible – if it has sunk beneath the wheelarch the (police spec) springs now need replacing.

  • The V8 rode on special Dunlop rims which used alloy centres, so expect electrolytic rusting between the two surfaces. Bear in mind that if you need new rims, the sort fitted to the limited edition Jubilee MGB are the same. Wheatley can now offer new period replacements.




  • The MGB GT V8 is brilliantly supported by the MG Car Club with its own registrar making one as easy to repair and maintain as an MGB, plus parts supply is generally fine.

  • Counterfeit Costellos! It’s not unknown for homespun conversions to be passed off as Ken’s work. Ask to see the car’s history and look for the unique Costello badging.

    Some DIY conversions are impressive but on others their standard of workmanship needs scrutinising and shouldn’t be on the road, warns V8 expert Clive Wheatley…


  • Swapping those rubber bumpers (only 735 were made) that added 70lb to the car’s weight isn’t a simple job as there’s some fairly major bodywork surgery involved. It can be costly too if a professional does it; £1500 or more and, besides, their rarity may be of considerable benefit in years to come.


Body and chassis


  • Any MGB’s monocoque is a real rust haven and V8s are no exception, providing plenty of places where you’re likely to find it along with bodged repairs. But if the worst happens and the shell really is beyond economical repair, you can buy a Heritage bodyshell costing almost 10 grand.

  • If you want to do it cheaper, then a second-hand rubber bumper shell is required as these feature the modified inner wings and front end that V8s featured.

  • Sills rot and are prime targets for bodgers, because repairing them properly is an involved process meaning removing front and rear wing sections.

  • Because they are tricky to repair properly, various ploys can be found. The first is to fit a cover sill, which simply hides the problem. The second is the use of a stainless steel over-sill, which looks pretty – but also masks potential problems. Best take a look from underneath and see that everything lines up properly. If the door windows clip the rear post, that’s a sign of poor fitment.

  • Look for soft inner wings – press the panel in the engine bay as a quick check and while you are there, inspect the chassis where the steering rack is located as these can stress crack. Unless you know MGBs this can be easily missed, even by MOT testers - but repair panels are available.

  • Check the back of the front inner wheelarches by first removing the front wheels. While you’re checking the rear wheelarches, take a look at the spring hangers, which may well be as rotten as a pair.




  • That V8 is lightly stressed and with regular oil and filter changes should be fine. However, infrequent oil changes cause the hydraulic tappets to play up due to sludging and they can become clattery.

  • As with all alloy engines, lack of sufficient quality antifreeze eventually leads to internal rusting. As the MG’s cooling system was stretched anyway, check for hot running – or over cooling if the thermostat has been removed. MG V8 specialist Clive Wheatley (01746 710810/www.mgv8parts. com) sells uprated radiators at a smidgen over £205 and are a wise replacement.

  • One essential check to save potentially disastrous engine damage concerns the thread on the bolt on the nearside of the airbox at the back of the V8. It should have a protective nut and serrated washer on it as the original ‘spot’ soldered bolt but often works loose and drops into the carburettor and on into the engine…

  • Is the unit standard or modded? As the capacity crept up to 4.6-litres it’s not unknown for a later engine to have been used. Failing this, perhaps the engine has been upped to 3500/SD1 tune.




  • The V8 used a modified and toughened up MGC gearbox with overdrive only working on top (although some cars sneaked through with it operating on third too, we’re told!). Check for undue noise, jumping out of gear and sheer wear due to hard use. It is vital to use the correct 20/50 engine oil in the standard overdrive and to keep the filter clean - but has it been done?

  • Clutch problems usually centre around the carbon fibre release bearing breaking up. Also make sure the pedal isn’t spongy. If it is, the hydraulics are on their way out.

  • Under all that power the MGB-derived rear axle may well have waved the white and become noisy and sloppy. Bank on a few hundred for a recon unit or you can have a limited slip alternative from MGOC for more rear grip.

Three Of A Kind

Triumph Stag
Triumph Stag
Major in-house rival to the MG, and also V8 powered, and with more bhp but the Stag has a lot less go. Initially Stags had snags but most are well sorted by now. Compared to a GTV8, a Stag can be half the price and there’s a specialist and club back up that’s as good as any MG support. Of course, many Stags were converted to similar Rover V8 power and these are good, if done right, although are now worth considerably less than factory spec cars. So if you’re after a V8 bargain…
People have been seeing the MGC in a different light over the past few years as its lazy nature has now become a virtue. That slogging straight six is slightly more powerful than the Range Rover-tune V8 but this doesn’t equate on the move. Handling, on modern tyres at correct pressures, is about the same as the BGT V8 but ride is better. Unlike the BGT V8, the MGC can be had in roadster and automatic forms and values sit slightly above the later model.
A case of third time lucky? Late in the day, MG Rover launched the best MGB V8 - almost two decades after the former MG company folded! Based upon the Heritage bodyshell with a full fat fuel injected 190bhp installed in a totally reworked chassis, without doubt it’s the best sorted V8 of them all as well as the most luxurious. The MG RV8 feels like a cross between a Morgan and a TVR but at prices comfortably less than the original Rover-powered road burner.


Pundits are predicting that the MGB GT V8 is on the verge of classic car greatness and the time to buy one is now before values really take off. It really is the Queen B providing the performance and character of an Aston and yet is as easy and low cost to keep as a normal 1.8. Plus, in GT guise, they look as good today as when the GT first broke cover half a century ago. Classy yet classless, what more do you want for so little?

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