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MG MGB Technical - MGB supercharger?

Hello all!

Thinking of getting a supercharger for my '72 B. Wondering about pros and cons as well as the place to go for the best price.

Thanks,

Shawn
Shawn Herndon

Shawn,

There is a supercharging forum with all the info you need. Look at the "jump to" box above and it is right towards the bottem of the list.

Iain
I D Cameron

Hi Mate

In My veiw this is a very expensive ooption for reletivly small gain, you can actaully fabracte a Turbo from a Metro to fit the GT block. OK yes Compression will have to be limited but so does the one on the Supercharger.

Easy to Install Cheap
Nat

A friend of mine runs a '65 B with a Moss supercharger. Nat, you're right about the cost. For me it's prohibitive - pretty close to $3,000 US. But Nat, the power gain on this car is HUGE. It has a couple of other tweaks too: multiple-spark ignition and a high flow exhaust. Low end torque is fantastic. I found myself driving this car in 4th-o/d on hills where I run my own Bs in 3rd. I just wish I could afford it.

Allen
Allen Bachelder

Between the blower and the V8 conversion, go for the V8. More power, reliability and most likely better fuel economy.
Then add the blower ;-)

Jim
Jim Blackwood

Allen; The car you describe sounds like the car that was parked near my car at the TCOC Gathering in Dobson, NC a few weeks ago. The owner gave me a description of what was done for performance enhancement. Starting with a new engine rebuild with plans for the supercharger by using low compression pistons. His engine builder balanced and blue printed the engine and did some head work. As you mentioned it had a custom twin pipe exhaust. It also had a custom cold air intake. If I remember correctly he said the car has 150 hp at the wheels. Just adding a supercharger will not give the power he has, I think it would cost over $10-12k to build a setup like his. Did I miss meeting you at the Gathering? We had to leave early due to some allergy problems from the grass.

Clifton
Clifton Gordon

Clifton,

Yes, we're both talking about Ken Brasfield's car. I've had the great pleasure of driving it quite a bit - and I have to say that whatever that car cost to build, it's WORTH it. That is not to say I could ever AFFORD it! Ken invited me to go down to the Gathering with him and I'm sorry to say I couldn't make it this year. I've had great times at Gatherings in the past, and I'll hope to make it next year.

Coincidentally, Ken and I both bought BRG MGC/GTs at about the same time. After about six weeks on the road, mine lost its second gear, leaving me 0 for 8 in the running-driving MG department. I'm putting a lot of time into my '73 GT to get ready to drive to NAMGBR in Olympia Washingon in not much more than a month.

Which reminds me... ' Gotta get to work!

Cheers,
Allen
Allen Bachelder

Hello all!

Thanks for all the feedback. From what I have gathered, it would be better to have a fresh engine rebuild to go along with the supercharger. Thing is though, my B looks good but has lots of cosmetic stuff underneath. Probably the best idea would be to sell mine and get one with a solid body in need of an engine rebuild. We'll see about that!

Shawn
Shawn Herndon

I know there's a s/c section on this BBS, but the contributors are all a little biased, I suspect, having forked out the dosh to get there! :~)

So, having been somewhat involved in a s/c conversion and now currently looking after the car here are my thoughts FWIW:

With any power upgrade there will be the associated costs of ensuring the car can handle and stop efficiently, so we can eliminate that aspect of the cost.

Secondly, if sticking with the standard B lump and tuning it, it makes sense to ensure the driveline is up to the task, and this may or may not include a change of gearbox. If one attempts the V6/8 route (or in the UK, the T or K series 4cyl engines), a change of gearbox is likely to be on the cards anyway.

Thirdly, looking at what an s/c offers in the way of power hikes, it is close to the figures for the factory GTV8 (74-76), which used a std gearbox with 3rd o/d blanked off. But, times have moved on and the current Rover V8 comes in 3.9 and 4.6L with >200bhp possible, which definitely calls for a new gearbox and numerous time consuming ods to the cooling and electrics etc.

If one already has a decent B series engine in a good state of tune, then it is saleable, to replace with a V8 for approximately similar money but considering all the mods with the cooling etc and the metal bashing to fit it and a new g/box, the time factor is lengthy, and the costs start to mount. A DIY approach could keep these costs down but the time is still an issue. With a s/c it can be fitted in a short space of time by a relative mechanical novice that would baulk at an engine swap, and it could easily be returned to std in a day or so which cannot be said for a V6/8 mod.

If one considers rebuilding a tired B engine first, before fitting the s/c, this would still have to be done in any case if the car were to be reliable, but with an s/c in mind, the level of build will depend on the anticipated s/c set-up. One could get away with a std 8:1 CR and minimise the boost to allow for a theoretical 11:1 CR. Anymore than this and it is necessary to start looking at a more expensive rebuild wrt pistons, cam, head etc.

I have no experience with the Moss unit, but it looks like a very easy weekend bolt in job. The one I do know is the Hi-Flow unit from Australia. Perhaps not as easy to fit as the Moss unit, it is still a neat looking job. The owner has made some mods to the cooling with two shrouded 9" units, but apart from that, he has stuck to a low compression rebuild with a special s/c head designed by Peter Burgess.

Now, for whatever reason, this car suffered a head gasket failure, but we think we know why, and it is now back up and running.

My own 1980 GT is a 1860, stage 2 head and 714 cam with K&Ns. It performs well enough by comparison to std Bs. Whilst a well set-up BGT will keep up with the s/c GT up to about 70mph, there is a big difference in how the s/c accelerates. It feels strong on torque throughout the rev range with much better pick up atlow revs, and does sound anywhere near as harsh as a std B which seems noisy/busy/fussy by comparison when accelerating hard.

The real difference is above 60mph. In 4th o/d, a prod of the throttle will have the s/c GT up to 90mph plus in no time at all and will prove a rude surprise to the driver of many a modern sports saloon! Whereas my GT just seems to take an age to accelerate from 70mph to 90mph. (Private test track, you understand!) I wasn't entirely convinced at first, but having had the use of this s/c GT alongside my own for a few months, I am fast becoming a convert! I can't wait until the s/c cam is fitted and some more boost is added beyond the current 7psi.

Whilst I won't argue at the aural pleasure of a V8, I think the s/c induction roar is also quite addictive.

Sure, there are any number of ways of achieving reasonable power hikes, and I won't deny that a top-end s/c conversion is not going to be cheap, but I suspect that any power hike that offers a recorded 110bhp at the rear wheels is going to be either expensive and/or time consuming with numerous teething troubles to iron out. The s/c seems to be the simplest DIY route to that kind of power without the additional hassles that an engine conversion would require.

In fact, given that Moss now also do an A series (midget etc) and another company also does one for the A series, plus, another Australian company, Sprintex, does s/c s for the V6 used in the MG ZS and ZT, I can see s/c becoming more popular - if only the price would drop a little!

Martin
Martin ZT

Hey Shawn,
I have been considering this for my '77B. I have spoken with mechanica and parts sellers that I trust and they have told me that before installing the supercharger you need to strenghten the bottom end.
I have also spoken to a salesman that said that all you need to do is bolt it on and away you go. I think that this fellow was full of SH---you know what. So look at the costs:
The supercharger is $3,000 US. Rebuilding the bottom end will be about another &2,000. So what if you said to hell with this and installed a 3 litre V8. This would cost around the same and you would have an engine that could really perform.

Just another thought.

Bob
Bob Anderson

...but you wouldn't have a vintage MG anymore. :)
Steve Simmons

Hi!
I installed a turbochager from a saab 900 and altough im still on fine tune im really pleased. turbo, intercooler and bypass valve were used, i made the exhaust manifold and the plumbing myself.
can somebody explain me how to insert a photo here to show you?
Thanks.





luis

We've done normally aspirated MGB upgrades, crossflows, superchargers, and engine swaps at our shop. People love to debate which is the best, but as a person whos tried them all, I love them all! They all have advantages and disadvantages and you need to match them to your desires, skills, and budget.

For a quick look at some performance differences, here are some dyno graphs that say a lot about what's going on. The graphs compare a 3.5L V8 MGB, a stock MGB, a supercharged MGB, and a Miata-powered MGB.

http://www.eclecticmotorworks.com/miatab6.html

--Carl
Carl Heideman

Shawn I''ve done it - so I'm biased -but its great. Martin & others outline the pro & cons of different ways of getting more power. I had a rebuilt standard engine and wanted more go to get past trucks and flat -cap Honda Civic drivers. - Not produce a fire breathing monster. It regularly surprises people as it looks very standard.

Yes it costs, but less than paying for the engine to be "breathed on" by a tuning shop. I don't have the skills or kit or space to "do" the engine but I can bolt on a s/c (Mine was from Moss) It comes with all the bits but get a new dizzy aswell.

Save up & have fun!!

Michael
Michael Beswick

Michael
Will you be at Silverstone - I am hoping to bring Phil's GT with the Australian Hi-Flow unit so it would be interesting to compare installations.

Martin
Martin Williamson

I've messed with small engines that are blown, multivalve untuned engines, and race tuned pushrod engines.

As others have commented, The supercharged engine typically has beautiful low rpm torque punch and pulls real strong up to stock top rpm. Feels like an engine with much more cubic inches. You don't have to shift down to get a punch in the back. The centrifugal blowers, like the Paxton, don't start producing much boost until you wind them up, and tend to build power as the rpms increase. Most modern belt driven blowers are (except turbos) positive displacement and not centrifugal.

The modified unsupercharged engine is soft off the line and won't do much unless you shift down. Once it gets some rpms, things begin to happen. Rowing that gear shifter to keep the engine in its power band is a necessity. Revving the engine is the key to going fast.

The multivalve engine with a tuned intake system can share the characteristics of both types. The Taurus SHO 4 cam engine built by Yamaha was comfortable putting around town, and then at about 3000 rpm that tuned intake system hit and things really began to happen. Now, with variable cam timing and tuned intakes, high rpm power is possible with low rpm docility.

A supercharger puts a load on the engine. Putting one on a tired engine is asking for a catastrophic engine failure.

You pay your money and take your choice.

Barry



Barry Parkinson

I can only agree with Barry about fitting a supercharger to a tired engine, you would be walking home for sure. You dont however need any more than a GOOD stock (including compression) engine if you keep your boost below 7.5lb and about 26* advance "initial + mechanical. The standard Moss SU needle is on the rich side which is good to start with and goes well but is a bit thirsty. A correctly curved dizy as Michael mentioned is a very wise investment but some of the early D25s if in good nick are suitable.
I went to Historic Winton last week and the racing was great with a number of very fast Bs Cs and Minis holding their own amongst the very expensive classics. Hans Pederson had a stand and a Bgt on show. It had a slightly different setup with the carby angled out towards the guard and a buypass valve fitted in the gap. It had his headers and an alloy radiator with dual fans,a very neat and professional job. I think it also had the bigger blower that he also fits. This carby setup makes fitting a cold air intake a breeze. Denis
D M HILL

This thread was discussed between 23/05/2005 and 06/06/2005

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