Tuning hints

[Bob Featherstone]

I have 'improved' my B as much as I can in the looks (inside & out) and in the handling and stopping departments. I have also done the usual and recommended things in the engine bay such as electronic ignition, K & N filters, full stainless steel exhaust system and the car runs very well and reliably indeed. What I have now is the thought that it would be even better if the performance was enhanced, without spending too much. Am I right in thinking that a higher lift camshaft (714?) would supply this without losing any flexibility. I would appreciate any advice anyone can give me.

[Peter Cresswell]

Hi Bob,
I would suggest you get a copy of 'How to Power Tune MGB 4-Cylinder engines for Road and Track' by Peter Burgess. Costs around £18 but it is packed with useful information and tips. In this book he describes all the various cams available for the MGB. The 714 has the comment 'A mild road cam that's only good for very high revs - doesn't seem to deliver anything!'. So you might find changing the cam alone is a disappointing mod to do for the money.
I am currently at much the same point as yourself with work on my B, and my preference having read the book, is towards the Piper HR285 Magnum which is described as 'An excellent road cam' in the book, but it does need 1.75in SUs (HS6s) to get the best from it. Sticking with 1.5in HS4s will help keep the bottom end torque, but you won't get the full benefit of the money you have spent it the top end of the rev range. The book also gives details of all the standard cams that were made for the MGA and MGB, and the cam specified for the early 18V engines has very interesting timing, and would appear to have a lot of untapped performance when fitted to a standard engine.
Some mods to the cylinder head will also help unlock a change of cam, which if done alone would only realise 3 to 5 extra BHP. The best head to start with is the 12G2709 casting which was found on MGB in the early 1970s and the Austin 1800S. This head has larger inlet valves (1.625in against 1.56in) compared to other castings (12G1326 and 12G4736), which provides better airflow. Peter does describe how to modify the head yourself (described by Peter as DIY head) and 'doing a head' yourself can be a very satisfying (if dirty) job.
Another source of good information on engine modifications is the Huffaker MGB Competition Preparation Manual, which you will find here:
http://www.mgexperience.net/article/mgb ... Manual.pdf.
Huffaker were based on the West Coast of America (Group 44 were similar on the East Coast) and raced MGBs in the SCCA championships, which only allowed the use of standard components, although they could be modified. So no alloy crossflow heads but unlimited modifications within the limits of standard castings. Unfortunately the camshafts they used are not available now, which is not a problem as they were totally unsuitable for the road. I have followed their guidance for the head I am preparing, with a few omissions to give good service life on the road as I don't want to remove the head every couple of hundred miles in order to reseat the valves.
A final thought, is a word of warning, which relates to where you live. You will hate an engine that won't tick over or has no power below 3000 rpm if every time you leave home you drive into heavy traffic!

[Peter Cresswell]

The cylinder head casting identification numbers quoted above should be 12H2709 (not 12G2709) and similarly 12H1326 and 12H4736. You'll spend forever looking for 12G versions as they don't exist. Sorry for the mistake.

[Bob Featherstone]

Thanks for your reply in detail, Pete. I was rather hoping for a power increase without loss of low rev flexibility. I have read elsewhere that the 718 cam is not as bad (high revs only) as it may seem and adds more to output. Maybe camshaft is not the answer and I also know I don't want to lose what I already have. Luckily I live in Devon (MG road county) but we still have traffic, particularly in the summer.

[Geoff Edwards]

Hi Bob,

I had my MGB GT engine rebuilt a few years ago with a fast road cam - despite having all the "right bits" it never seemed to go well. Having read Peter Burgess's book, I came to the conclusion that one had to go a long way to beat the standard spec camshaft; largely on the basis that with other cams whilst there may be some positive gain there was always a negative. So last year I fitted a new standard cam; with some foreboding, I followed the current advice on running/bedding in the cam; this is to immediately run the engine at approx. 2,500 revs for 20minutes. I worried whether the oil pump was primed properly and whether I'd used enough cam lube, but all was well and now the car really does go well. The engine is also a lot quieter than previously - the valve gear was extremely noisy to the extent that people made very rude comments whenever I drove up!! I now set the valve clearances using a dial gauge.

From my experience I think you are right that "Maybe camshaft is not the answer"
Geoff

[Peter Cresswell]

Hi Bob
Supercharging would do the trick - about 40% more torque and a similar power gain. Only problem - £3,500 for the kit and setting it up!
As Geoff says above, maybe a cam is not the answer. To mention Peter Burgess' book again, in the Power Recipes chapter his standard class race engine produces 95bhp at the wheels (about 135 bhp at the flywheel) - a standard B which uses all the same parts is 60 - 65 bhp at the wheels. A lot of detailed work goes into his race engine, as it 'blueprinted' but it does run a standard cam. I know knowledge has moved on a bit but the Le Mans MGBs from the mid 1960s were Stage 5 tune giving 130 bhp, but there is potential in the standard cam.

[Dave Linkson]

Hi Bob,
I was put off from supercharging the B engine by very a very experienced MG conversion specialist, saying supercharging can lead to head gasket failure.
If your engines done many miles maybe do a cylinder pressure test. Possibly a rebuild would be in order, or if all ok on the bottom, at least have a top end rebuild with new standard camshaft and port & polished cylinder head.
Peter Burgess doe's an Econotune head which would give more grunt..