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MG MGB Technical - Horse Power

Hi all,
I need to know the Horse Power of my 1979 MGB Roadster fitted with a Stage 2 1860 cc Engine.
I know the approx BHP but the actual Horse Power is required for French Registration if anyone can help it would be appreciated.
Thanks in advance
M.J Egan

are you sure you're not mixing the two up, its more likely you hp rather than bhp of your engine so use the figure you know
Nigel Atkins

I have a feeling the French authorities use an old fashioned formula for registration (as indeed we did) - thus the "Deux chevaux" (or the Austin 7)
When the MGB was introduced to the French Market - it was officially rated and somewhere in the Boulevard Saint-Germain a French official will be sitting on a type list.
The fact that the car has been modified is irrelevant - unless you want to make life difficult for yourself.
Roger W

do you mean like the very old tax class where a '12hp' car wasn't necessarily 12hp?
Nigel Atkins

Hi Nigel
No mix-up, they need the hp not BHP my roadster certainly doesn't have a 65 horse power engine
M.J Egan

A 1798 cc MGB engine is 16 tax horse power ( RAC HP )
Chris at Octarine Services

sorry I didn't make myself clear and it didn't help by my missing a word out

I meant that it's you that's mixing up the two, it's more likely that you know the hp of your engine

this figure you have mistaken for bhp

what figures have you got and what do they relate to e.g. at flywheel fitted in car, at driven wheel including losses, engine claim, etc.,

ETA: possibly I've posted too late and it's resolved by Chris's post
Nigel Atkins

I wonder if Roger is giving you a hint - perhaps you want to check out some expert specialist advice before you fill the form as it may not be to your advantage to have a 1860 engine or higher hp

some countries seem to be a lot stricter about changes from standard than the UK
Nigel Atkins

It may be the French authorities calculate the CV (horse steam) differently to how the UK did.

The number of French fiscal horses is the result of an obscure formula taking many different factors into account. The prefecture will calculate it if you don't know it.
Chris at Octarine Services

See Wiki
Geoff Ev

Geoff - that only covers modern cars where the emissions are part of the type approval - i.e. cars built after 1998. Still safest to ask the prefecture to calculate it for the specific car.
Chris at Octarine Services

Thanks a bunch fellas, I'll go for 16 hp and let them tell me if they know different
Thanks again
M.J Egan

Hi - I have just had an email from a customer in France with an MGB GT and he says it is 10 CV!
Chris at Octarine Services

Good answer - I think we are all singing from the same hymnsheet.
Roger W

check Wikipedia:

Have fun!


Siggi, You really put the debate on something of a higher level.
Interesting but too deep pour moi
M.J Egan

er, it's the same link Geoff gave earlier in the thread
Nigel Atkins

uuups, sorry for not reading all of...


my comment was more for MJ

don't worry about missing posts some don't bother to read most previous posts anyway

better to have information twice than not at all
Nigel Atkins

Mine's (1800cc) rated at 10CV.

Just make sure you tell them the car is a standard 1800cc, and standard everything else.

Anything else will be making a rod for your own back.

I had my Suzuki Bandit bored out from 600 to 884cc making it instantly illegal in France.

Just for info:

Our normally aspirated 2.2 ltr Renault Laguna 98bhp diesel is 7CV.

Our turbo 2.0 ltr VW Passat, 140bhp diesel is 8cv.

You work it out!
John Bilham

Lol - don't try and work it out - they are just taxation classes - I still can't reconcile how my 1.4 turbo diesel van costs 220 a year and the exact car equivalent costs only 30! My 6.5 ton HGV lorry is on;y 165 ...
Chris at Octarine Services

Here is a link that seems to provide the answer:

Up to 1977 it was a simple calculation based on engine dimensions and would make an MGB 10CV

From 1977 on it is engine displacement, fuel type, number of gears and gear ratios! Makes an MGB around 16CV if you count overdrive as 5th gear, 17CV without overdrive!

Richard Wale

Mine's 1977, 10CV.
John Bilham

This thread was discussed between 16/01/2014 and 24/01/2014

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