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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - That lovely, lovely, troublesome Twin Cam engine

I don't have to say it - I know you all feel the same - but that Twin Cam B-series unit should have become MG's mainstay.

I don't have to say it - I know you all feel the same - but if the engine was troublesome, it gave the A such cachet.

And I don't have to say it - I know you all feel the same - but the A we all want to own is the Twin Cam.

BMC could do some very interesting stuff, but it didn't always follow through. When BMC felt brave, it could do stuff like the Mini. And like the Twin Cam engine the early Mini had its faults. Notably the ingress of water. But in the Mini's case BMC didn't give up: it saw enough promise in its baby that the company tooled up for a new floorpan so that the little car didn't leak (or leak as much.) And this was all back in the day when the Mini was teetering on the brink of failure.

So it seems such a lost opportunity that the company
didn't feel inclined to persist with the Twin Cam unit and attend to its problems.

My question is: did the five-main bearing B-series make such a material difference to the engine's bottom end strength to negate the earlier problems with the three-bearing engine?

This from David Knowles' excellent book, "MG: The Untold Story":

"Because of the desire to use the [Twin Cam] in serious competition - and to take advantage of the superior performance at high engine-speed of twin-cam engines - it was decided to make the crankshaft webs thicker than those of the pushrod unit. This meant that the main journals had to be correspondingly narrower, and although the bearings were changed to a heavier-duty type and used with a new design of competition conrod, this led to inherent weaknesses in the engine under load."

Would the five-bearing redesign of the B-series' bottom end have alleviated this problem? Could a lower-compression (than the 1600) five bearing B-series Twin Cam have been the sporting, reliable thoroughbred engine the MGB deserved?
Steven Perkins

Steven:

There is really no reason for my comment other than to stir controversy, but having said that I wanted to go on record as being at least one BBS member who has never wanted to own a twin cam engine. Over the years, I have passed on numerous opportunities to own them and feel no remorse beyond, perhaps, as an investment. It might also be fun to have one in the family room as a conversation piece.

IMHO the engine was "optimistically" designed, mechanically fragile and did not add the performance that compensated for the maintenance. It was okay for a dedicated racer who expected frequent tear downs, but even in the hands of true car experts (and fanatics) was not consistently competitive in its class during the years of its production.

I love my MGA, having owned it for forty one years. I also love mechanical complexity and cars in general. However, in truth, the twin cam engine was not particularly well-engineered and except for its scarcity and novelty for a car the price range of an MGA during the period, I can't see the attraction. Evidently, the car customers of the time felt likewise.

As far as the evolution of the engine, from its inception, the twin cam was not well-supported by the factory - even for racing. Furthermore, there is little or no evidence that the conservative mentality that made resource allocation decisions in the British car industry would have supported the kind of engineering and production dsevelopment costs necesary to make the twin cam commercially viable, much less a mainstay of the marque.

Let the hounds of MGA hell be unleashed...


Steve
Steve Brandt

You really have owned, and to have raced, a mga twin cam to understand the strengths and weaknesses of the engine.
They were mainly commercial reasons behind existence of the Twin Cam and also the reasons for its demise.
It was decided by BMC that they urgently needed a car to sell against the Triumph TR in the USA, a genuine 100 MPH car with overdrive. The first mistake made was to direct the designers that the Twin Cam block must use the bore centers of the transfer boring machines at Longbridge. This completely dictated the engine design.
The comment has been made that the bearings had to be of a special type (lead-indium) and to increase the crankshaft web size the bearings were narrowed. This is true, but it was never a problem. In fact the thicker webs and narrower bearings were so successful that the setup was used on the 1622 MGA 1600 MKll.
There were several minor, easily fixed problems, such as the need for a stronger chain adjuster, stronger gears driving the oil pump spindle etc.
The two big problems were the fracture of tappets (cam followers) and the melting of piston crowns. Unfortunately the engineers working on the engine were too slow in solving the problems. They went down dead end paths in trying to fix these, making changes that did not help. They solved the tappet problem (metallurgical composition), but too late. The car had received a bad name in the USA and was hurting other BMC sales.
They never solved the piston melting problem, but managed to hide it by lowering the compression ratio from 9.9 t0 8.3 however Twin Cam owners solved it (fuel starvation due to SU vibration).
Had these two problems been solved quickly the Twin Cam would have remained in production much longer.
The MGA Twin Cam BBS currently has about 330 cars with satisfied owners.

Mick
Mick Anderson

Mick described it very well. No inherent weakness in the crank.

You have to drive a Twincam to appreciate them (I race one). It is almost a totally different engine than the pushrod.

If we'd had an MGB Twincam.....mmmmm


Bill Spohn

What about if it had been put into the car it was originally intended for - the MG Z-Magnette. I read that one was transplanted subsequently.
Dan Smithers

As the owner of two twin cam engines I'd have to agree with Mick, it's a shame MG did not solve the problems earlier.
As we know with ex181 fitting an enormous blower gives nearly 300BHP, still impressive these days.

http://www.mgcc.co.uk/Pages/News/070820_Moss.htm

These engines still has plenty to give even these days.
I'm in the early process of trying to build the MGB 1800 twin cam. Not an easy task but it should provide an exciting drive if I can keep the weight down.

Cheers
Mark.

Mark Hester

For those who think that the MGA Twin Cam engine had a weak bottom end I have attached a photo of the record breaking 300 HP engine to which Mark refers.
It had various modifications, but still had the main components, including the cylinder block.

Mick


Mick Anderson

Mick, I have wondered this question many times,but have no good answer,maybe you know. Alfa Romeo at the same time was building train loads of twin cams with much success and of similar sizes. What was MG's reason not to use the same metallurgical process. Alfa's had the same and higher compression ratios. What was MG thinking?
WYATT WOLCOTT

Hi Wyatt,

There were many Twin Cam engines built before and during the MGA Twin Cam period. You mention Alfa Romeo, but more importantly the XK Jaguar twin cam engine was built nearby. This engine was very successful, especially in long distance races such as the LE Mans 24 hour race. The XK engine has lighter and smaller tappets (Jaguar 1" long versus MGA 1.5").
When the MGA tappets started to fracture the MG engineers could walk down the road and buy Jaguar tappets from the spare parts dealer and look at the design and metalllurgy, instead they made the MGA ones larger and heavier.
Why didn't they look at Jaguar items?
I attribute it to professional snobbery.
The same can be explained with the leaning due to SU vibration, the Coventry Climax people had already solved the problem by "soft mounting" the SU carbs.
The demise of the MGA Twin Cam can be blamed on a mental attitude of several people in the Company.

Mick
Mick Anderson

That blower is as big as the engine. Any idea where I can get another one.... Please.....Pretty Please.....
dominic clancy

Dominic

I suspect it is a reheated Rolls Royce Avon jet engine as fitted to the BAC Lightning (as per my photo). The twin cam engine was used to pump fuel to the afterburner unit!

Massive isn't it. Bit of a struggle to get it in an MGA engine bay.

Steve
Steve Gyles

As the owner of a blown ZA Magnette (with a much smaller blower than EX181!)I will admit to having considered building a Twin-Cam for my car.
Unfortunately it will have to wait until my lottery win comes through as I don't have the extra $10-12,000. on hand to carry out the project.

sigh*

Rich (but not wealthy!)
Rich McKIe

I have owned my 1956 MGA since my College days back in the 60-70's. I have always wanted a Twin-Cam powered MGA. I have never heard one run or ever road in one but
have talked to people like yourselves and enjoyed hearing about those cars. Some day I hope to be a very proud owner.
Tom Peotter

Tom, you too can have a 140 BHP Twincam powered MGA.

As long as you don't mind the engine being more powerful than the original, nor the Miata lettering on the cam covers.

Here is a picture of a local MGiata (the car was originally an MGA Twincam that had the MG engine removed years ago).


Bill Spohn

Just out of interest on the Jaguar XK unit, didn't the company propose a 2-litre four-cylinder twin-cam when the six-cylinder unit was unveiled back in 1948?

And didn't MG itself use a twin-cam Jaguar XK four-cylinder unit in one of its record-breakers. EX135, perhaps?

Given that I believe BMC was in cahoots with Jaguar developing a new V4 and V6 in the late 50s, you might be forgiven for thinking that Longbridge would have been better off snaffling the rights to the four-cylinder XK instead of going it alone with the twin-cam B-series. A two-litre twin-cam A: what a car that would have been and you have to suppose that the engine would have been more reliable than the unit we got. On the other hand the Jaguar unit was probably too big, and too heavy to fit in the A's snub snout.

Still, the Jaguar XK4 unit must rank as a missed opportunity for someone. Considering that Jaguar didn't use the engine itself, what might such an engine have done for Healey, or Triumph or any other number of defunct British marques back in the day? And it was there for the taking...

On the subject of a twin-cam 1800cc B-series, Mr Hester, the world awaits. That sounds like a damned fine car.

On the subject of the B-series itself, I think that the old thing probably should have been subjected to an ongoing development programme - including the Twin Cam. In hindsight the B was the only engine BMC ever really needed for its medium to large saloons, and sportscars. In the Sixties a two-litre unit was experimented with, and BMC Australia, of course, built its own six-cylinder variant, the Blue Streak.

Instead the company spent a not inconsiderable amount of capital developing the unhappy Austin Maxi E-series OHC four-cylinder (with a six-cylinder offshoot) and the equally unfortunate New C-series engine as used in the disappointing MGC, and the unlovely-if-interesting Austin 3-litre saloon.

Consider this: with a bit of development BMC could have revamped the B-series to provide 1.6 to 2-litre fours, corresponding diesel units, and 2.4 to 3-litre sixes. While it was about it the company could also have found the inclination to nail the Twin-Cam's maladies.

In other words, the B-series could have been developed to do the job that three different engines ended up doing.

And another thing: independent rear suspension. Why BMC thought this was desirable on its off-roaders (Champ, Gypsy, and the abortive ANT), and its front wheel drive saloons, but not its rear-drive saloons and sportscars escapes me.

Anyone got a time machine, or can anyone here travel to a parallel universe? Because I want to bag myself a 2-litre MGB Twin-Cam with IRS, and to hell with the MX-5.


Steven Perkins

Hi Steven,

Yes, Jaguar did build a four cylinder XK engine. I have examined the actual engine that was produced. There is one in a motor museum in the city of Fremantle in Western Australia. I have attached a photo.
The Jaguar engine could not be produced on the mass production engine line at Longbridge because of the bore centres and BMC was not interested in using the Jaguar engine supplied as a complete unit.
You mention Triumph. They had their own 2 Litre Twin Cam engine. It was raced at Le Mans. It only had one easily fixed problem, excessive wear of the valve seats.
It was dropped in favour of a six cylinder pushrod engine (easier to produce).

Mick


Mick Anderson

Hi Steven,

Just for visual comparison with the MGA Twin Cam engine I have attached a photo of the Triumph Twin Cam engine. It was known at the factory by the name "Sabrina".
I suppose that you are not old enough to remember the British actress called Sabrina. If you are of that vintage you will see the connection.

MIck


Mick Anderson

Hi, Mick, and thanks for those images. The Jag engine especially looks darn neat.

No, I am not old enough to remember Sabrina Duncan (was it?) but I remember reading a Graham Robson article somewhere or other which related the reason for the comparison. Apparently, like the twin cam units we have already mentioned, Ms Duncan herself featured a very impressive top end, but I hope for her sake that her units didn't prove as troublesome as the A's, or need the attention of sympathetic mechanics to remain on song quite so often.

BTW, I reckon that Triumph unit could have given the Massey-Ferguson tractor the performance it deserved.

On the Jag-BMC connection and the BMC V4/V6 engine. I remember reading an interview with Don Hayter in "Classic Cars" in which Mr MGB stated that BMC was designing the engine with Jaguar in the late 50s, so at that point at least Longbridge appeared to have the investment to replace the B and C-series engines. If only Sir William Lyons could have persuaded BMC to tool up for an "XK4" instead...

I reckon that such an engine would have been right up Syd Enever's street, because he's said to have hated the V4.

If BMC built the Rolls-Royce B40 for the Champ under licence, maybe they could have obtained a licence to produce the XK4 under licence too? I only ask because
it might have been a cheaper option that the V4/V6 family.

Then again, if the Jag engine appeared in 1948, Leonard Lord should have beaten a path to Sir William Lyons' door that year before the B and C-series ever saw the light of day. I'm waffling now.



Steven Perkins

Hi Steven,

The British actress in the 1950's known as Sabrina was real name Norma Sykes. The Triumph Twin Cam engine was named after her, for obvious reasons.
Compare the previously attached photo of the engine with the real Sabrina on Ebay. http://www.ebay.com

Search for item 260177722810



Mick
Mick Anderson

Another interesting MG/Jaguar connection.... The 1984 MG Metro 6R4 rally car used a twin cam V6 engine developed from the Rover V8. This engine, with further development and turbochargers added, was used by Tom Walkinshaw Racing's 1991 Jaguar XJ220.
k v morton

My "A," by the way, is now "B" powered, but getting back to the original thread, I would love to have a Twin Cam.

Ken
k v morton

This thread was discussed between 28/10/2007 and 06/11/2007

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