Tuning the B Series

Obviously, with the years the B series has been around, not only has everything been written about tuning it, but also just about every trick, and then some, in the engineering handbook book has been tried.  I would suggest if you are interested in further reading on the B, then look no further than Peter Burgess's book: 

"How To Power Tune MGB 4-Cylinder Engines" 

(Peter Burgess; Speedpro Series; Veloce Publishing; 1996; ISBN 1-903706-77-7) 

I have to admit that this book was bought for me shortly after I got my BGT, and it was, in part, what got me into tuning my engine.

Reasons to consider upgrading the B series.

The foremost reason for tuning a B series, in my opinion, is that owners want originality but want that little bit more from their car.  The upside is that there is plenty of information on the matter, and no shortage of skilled specialists to undertake the work, especially in the area of head porting.  The originality aspect will obviously maintain resale values and in many cases, the work is not discernible from the outside of the engine.  For many, the attraction of B tuning is possibly that the nature of the B is not lost - done in a restrained manner, reasonable power gains of 10-20% can be attained without losing that "torquey" nature of the B which makes it so popular on the classic car scene.  The biggest attraction is the relatively low cost of tuning possible by the less ambitious home mechanic.

The downside is the fact that the engine still weighs a lot, (a figure of around 200kg is often quoted for the engine alone).  Whilst weight can be lost in other areas, I think the fact that nothing ultimately changes means the weight balance will not be affected and so the handling of the car will not change either.  If you have a perfect set-up to your liking, then this is not disturbed.  Apart from weight (and the relatively low gain for the power hungry), the only other downside might be that if the approach is not considered as a whole, then mis-match of parts might lead to annoying issues that will become expensive to resolve.

On the cost side, though, whilst it is a relatively low cost upgrade, this is, in my opinion, only so if you are already faced with an engine rebuild cost.  To upgrade a perfectly healthy B series unit is going to be more money than including some of the modifications during a standard rebuild.  For example, the fitment of the cam, the use of maximum oversize pistons, and the fitting of a Stage 2 head will only increase the engine rebuild cost by the extra cost of the up-rated parts.  As an example, although you could buy exchange reconditioned units for £700, if you were to have your engine rebuilt, the quote I received was around £850.  However, to balance the unit, skim to a 9.75:1 CR, add an 1860cc overbore, 714 cam, and fit a Stage 2 head only added a further £300 to my quote - money very well spent, I feel.  As to the other issues such as distributor and carburettors, again these are likely to need upgrading and the additional cost of up-rated units is small by comparison, in fact possibly even less when considering an EDIS compared to a rebuilt Lucas distributor.

Having covered some 8 000 miles in my rebuilt engine I would say one of the benefits of this limited tuning is the B's reliability and tolerance of carburettor adjustment and timing is retained.  Based on comparisons against standard cars and other people's experience of driving mine, the car is surprisingly quick, although not necessarily comparative with today's lighter, ECU managed modern cars.  However, adding K&Ns with AAA needles, and fitting the EDIS system has made it a smooth, more free revving engine, yet still with the characteristic note and feel of the original unit, and it won't disgrace itself that easily against newer cars.  At this stage, perceived wisdom is that larger 1.75" SUs or Webers are simply not necessary unless you spend a lot of time at WOT (Wide Open Throttle)!

Beyond Stage 1 & 2.

Going to Stage 3 and increased capacity is going to be much more expensive although it will net some impressive power gains of up to 140bhp or more.  This will entail significant work on the head and block, and as the adverts say, only the best blocks can be used for the enlarged capacities of 1950cc up to 2100cc.  Evidence from owners suggest increased oil consumption is a risk on larger capacity units owing to the flex that occurs around the piston rings when the stiffness is lost after over-boring.  For further information I strongly suggest reading up on this in the book mentioned above, or talk to Chris Betson of Octarine Services.  However, having driven Simon's BGT with a standard tune 1950cc engine, it does offer more noticeable torque, if not as free revving as my 1860cc unit.

Cross-Flow

Cross-flow as a concept to improved power is not new in the MG world and even back in the 50/60s, Derrington were offering a cross-flow head.  However, today, it is Webcon with their MSX head that is being offered as an all alloy construction.

However, with the B Series having both it's distributor and oil filter on the right side of the block, the fitting of carburettors (SU's or Webers) will mean additional hassles at service time.  Therefore, I would consider remote mounting the oil filter as per the V8 on the inner wing, where it will make for cleaner oil changes, and then fitting EDIS to eliminate the need to access the distributor.  In fact the head lends itself very nicely to the concept of throttle bodies with fuel injection, and if the EDIS is fitted, then some of the management would be in place already to employ the injection system.

The picture above is a car that belongs to Cameron Gilmour of Bumper to Bumper British Classic Car Spares and was featured in the Feb/March 2003 edition of MG World magazine.  It has a tested 180bhp output.

Chris Betson of Octarine Services has also built a cross-flow engine and can supply the cross-flow heads although he recommends having them ported to get the most from them.

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