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MG MGB GT V8 Factory Originals Technical - Cost of conversion in UK

I want to join the ranks of MGB GTV8 owners soon but I have a dilemma! In the near future I shall receive a cheque for several thousand pounds from a matured insurance policy. Do I get my 1977 GT converted - it's in good condition apart from one or two small rust bubbles - or do I sell it and buy a factory V8/after market conversion? My current car was checked out for the PO and passed OK in 2001 for a V8 conversion, but it was never done.

How much would you expect to pay for a professional conversion? I'm looking for around 200-220bhp from either a 3.5 or a 3.9 engine.

Any thoughts and advice are welcome!
L Webb

I notice that no-one has answered you - bacause your question is impossible to answer! I'm sure you know that the original factory V8 only had about 137 bhp - not that it wasn't a good car, but it doesn't match with your 200-220. The performance offered by the car is more down to the huge torque than to the bhp.

If you bought a factory car, it might have more problems than your own car. You could say better the devil you know than the one you don't, but conversions done professionally cost a lot of money.

The engine alone could cost you thousands if you are buying new or properly reconditioned. What about a gearbox? You could use the original MG box, but not with 220 bhp. So you need to factor in a Rover box as well and the tunnel mods necessary to fit it. You will almost certainly want to have the axle ratio altered - more expense. Should you uprate the brakes? Or suspension?

Can't tell you what to do. You need to do lots of research for yourself, trawling websites and getting info and prices.

Mike Howlett


Many thanks for the response - much along the lines of my local mg specialists whose reply was "How long is a piece of string?"! They reckon from 3000 upwards for a "standard" 3.5litre with proper V8 4+o/d box and MGC rear axle. My brakes are already uprated so would be OK and I was thinking about uprated suspension anyway - even if I didn't fit a V8.

I was hoping for a response from someone in UK who has had a V8 conversion done for them recently, but I'm going to look at a factory V8 on Saturday - the V8 owners in my local MGOC reckon I will be pretty impressed with the performance of an unmodified 3.5V8 anyway. My current GT has a 1950cc engine with K&N filters and electronic ignition. Two 1800cc B owners who have ridden with me say it is certainly quicker than standard.

L Webb


I was waiting for your last post on subject as excellant summation of whats needed.

It is probably more worthwhile to convert a roadster.

A few months ago Retro cars had an article on Sebring conversion on a budget for 5k, but its better to convert a knackered car than a good condition car.


There are also quite a few ready converted cars around for sale. These are non-factory and tend to have the higher bhp figures you are after. Check the adverts in magazines (I know there's one in Retro but it's a bit of a monster)
Stuart Robson

To L.Webb

I think the most relevent point here is do you want the pleasure (frustration) of building it yourself?
If you are going to pay someone else to do it for you it is likely to cost you a lot more than what you can buy a good spec converted car for.There are a few on e Bay UK at the moment, a nice roadster in Brooklands? green just sold for £7.300.00 which would seem about right a very high spec V8 Sebring GT failed to sell, ie withdrawn when the bidding reached £9.100 + 5% commission. A normal converted V8 GT could be anywhere from £3500 up depending on spec and condition.There is a guy selling a Kit of parts including a sebring converted shell engine and all parts to complete ( he says) only at £510.00 so far if I had room I would probably have a go myself.
Hope this helps to clarify the position.
Good luck,
Kevin Jackson
K.R Jackson

How about going to RPI Engineering and asking their opinion.
Tony Bates

I have a factory B GT V8 which I have owned from new.

I would be inclined to buy the best factory car that you can find, irrespective of the condition of the engine and gearbox.

Then as budget permits swap the gearbox for a Rover R380, which can be purchased new, 2nd hand or refurbished; and the engine for one which suits your purposes.

I would buy a NEW Rover V8 from John Eales, a choice of capacities from 2.5 to 5.2 litres and a large choice of compression ratios.

John Eales is nowhere as good at websites, publicity and communications as Chris at RPI, but IMHO he is the man. He's built me 2 V8's, 3.9 litres & 4.6 litres - I wish I'd put the latter in my B!

Whoever you buy an engine from go for a new 4.6 cross-bolted block - it's little cheaper, but vastly better than a rebuild.

I'm French, but I have bought all the parts fitted on the car in England. 220hh with a 3.5 engine is not easy and cost a lot of £. The car is very altered, shell, suspension, brakes (AP racing all round), LT77 close ratio gearbox, ATB Quaïfe diff, etc…
A good car, the parts cost to me 33000£.

Michel - la page ne doit plus exister?


Sorry,little data processing mistake

Thanks - very nicely done.


Thank you all for your help/opinions. I have decided to buy the factory V8 that I went to view today. I was certainly impressed by the overtaking capability - even in 4th gear. It will be a week or so before I collect the car. Price was very good, engine/gearbox fine, N/S front wing needs a little attention but the money I get from selling my much loved late 77 BGT will more than pay for the repair. Only wish I could keep both cars!

L Webb

This thread was discussed between 14/09/2004 and 18/09/2004

MG MGB GT V8 Factory Originals Technical index

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