MGC Roadster and GT Coupe

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1967 - 1969
6 cyl.
2912 cc
150 bhp @ 5,250 rpm
4 spd. man & overdrive / 3 spd. auto
Top Speed:
125 mph
Number Built:
4 star
Reviewed by Unique Cars and Parts
Our Rating: 4


Right from the get-out, the MGB was a tremendously popular sports car - great looks, affordable and great fun to drive. In fact the only criticism after 4 years of sales was that the car could do with more power.

The answer came in 1967 with the MGC GT Coupe and Roadster, which featured the new BMC 2912cc 6 cylinder engine - similar to those that had been used in the Austin-Healey 3000 Mk.III. Similar but not the same, as the new engine featured seven main bearings compared with the C-series four.

That said, the engine was still a rather old-fashioned design, with overhead valves operated by push-rods and rockers from a side camshaft and breathing through twin SU HS6 side-draught carburettors. Exhaust and inductions were both on the left side of the engine. The crankcase ventilation was sealed, using a Smiths valve with an overflow tank for the cooling system.

To shoe-horn the bigger engine into the MGB, the engineers removed the small bulkhead that sat just ahead of the 4 cylinder engine altogther. At the other end, the engine extended into what was otherwise wasted space. To clear the top of the engine, a substantial "power bulge" had to be formed in the bonnet, accentuated by a transverse chrome strip.

There was also an additional swelling in the main dome to clear the top of the forward carburettor. These expedients are the answer to anyone who wonders whether the old Austin-healey 3-litre engine could have been fitted into the B instead.

The maximum power developed by the new unit was the same as before, being 150 bhp @ 5,250 rpm. Compare that to the 95 bhp @ 5,400 rpm from the 1798cc 4 cylinder engine fitted to the "B" and it shows just what a jump in performance was on offer.

The "C" boasted a top speed of 125 miles per hour, with maximum top speeds in gears being 36, 62 and 96. BMC claimed the "C" could reach 90 mph in 20.2 seconds and the standing quarter mile in 16.8. Because of this much higher speed potential, the wheel size was increased from 14 to 15 inch, and Dunlop SP41 tyres were fitted as standard - although wire wheels were a listed option.

Of course the larger engine meant there was an effect on the weight distribution of the car, the weight being carried by the front wheels going from 52.6% to 54.8%. The engineers knew this would have a negative effect on braking, and so re-calibrated these accordingly. The diameter of the front discs was increased from 10.75 to 11 inches, while the rear drums were decreased by 1 inch (from 10" to 9"), although wider shoes were fitted, up from 1.7 to 2.5 inches. A servo mounted on the bulkhead, to the left of the engine, was standard.

There were few internal differences between the MGB and MGC. A push-pull headlight switch replaced the previous tumbler switch, and was mounted above the oil pressure and water gauge - although this change to simplify the switch layout had been in production for some time on the MGB. The most obvious changes on the "C" were the rev counter, which was marked up to 7000 rpm, having an amber sector from 5,200 through 5,600, whereas on the "B" this warning extended to 6,000 rpm.

The MGC also had the speedo re-calibrated up to 140 mph. Reversing lamps were standard, and the fuel tank capacity was increased from 10 to just over 12 gallons. A major change on the MGC was the use of torsion bar independent front suspension in place of the MGB's coil spring layout. The space problems and need to remove the strong cross member, and transfer suspension loads from the extreme front to a point farther back, were the reasons for this change. Telescopic dampers were used, in place of the MGB's lever arm dampers; and there was an anti-roll bar. The rear suspension condinued with the seim-elliptic leaf springs and lever arm dampers. It was not only to counter act the increased nose weight that a small reduction had beem made in the steering ratio; it was altered primarily because of the increased skew angle to the rack and pinion steering box, dictated by the wider engine.

Small Window Click picture for close up view
A new four-speed gearbox was fitted with the same ratio's as before, the most important difference being that it had synchromesh on all forward gears. overdrive working on third and top gears was available as before, and when fitted to the MGC the final drive ratio was lowered from 3.07 to 3.307:1. In top gear, the standard MGC ran at 23.8 miles per hour @ 1000 rpm, while with overdrive the gearing is exceptionally high at 27 miles per hour @ 1000 rpm. That meant the "C" could cruise comfortably at 100 miles per hour ticking over at just 3,700 rpm.

And just as the new engine had done, fitting the appreciably larger new gearbox required some modification, the transmission tunnel being enlarged in the body structure. The up-side was that, after the work was done, it was realised that there was now room to accomodate the Borg-Warner 35 automatic transmission. It was soon listed as an option for both the MGB and MGC.

The selector moved through a straight notched gate, with operation requiring the lifting of a "cotton reel" below the knob to safely step between positions. The L2 position provided a positive hold on the intermediate ratio without excluding bottom gear. With L2 selected the MGC would start in first gear, make a normal change to second (intermediate) and stay there regardless of engine revs until the selector was moved to the "D" position.

85 miles per hour was possible in second, and a big advantage over the more usual Borg-Warner 35 controls used at the time was that L1 could be used to hold first gear up to peak revs, and then by moving the lever to L2, the transmission changed into intermediate gear even if the full throttle kick-down was not in use. Instead of being illuminated from underneath, the designers incorporated a small map reading lamp that shone down on to the selector control.

On the road, the engine demonstrated its dislike for the cold as per the Healey's six, being lumpy and prone to stalling when first started. Once the engine was a little warmer, it settled down and became smooth and, when compared with the 4 cylinder unit, very impressive. Obviously the manual transmission had the wood on those fitted with an auto, the relatively high gearing making it a spirited performer and quick off the mark. A good torque band meant you did not have to work the gearbox as vigorously as with the 4 cylinder.

But there was debate about the suspension changes made, many believing the handling was simply not up to the performance on offer. Some of the very people that had called for more horses to better exploit the MGB chassis were now calling the new iteration a dud - if only they had bothered to tweak the suspension a little more and fitted better tyres they may have been convinced. But the damage was done, and the MGC only remained in production for 2 years. Today more far-sighted enthusiasts appreciate what the car has to offer - they are now extremely valuable and highly collectable.

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Also see:

MGC Technical Specifications
MG Heritage
The MG Story
MG Performance Chart
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