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MG MGB GT V8 Factory Originals Technical - V8 conversion in 1976 MGB GT - Info needed

Hi all,

Quick question, just getting some info on a V8 conversion for my MGB GT.
Can I use my existing gearbox ?
Is there an adapter I will need?

If anyone is in the Midlands, i'd love to see your V8's!
Please drop me a lin, cheers.

Paul

Paul Elwell

Paul

Yes, you will need a different gearbox unless you intend to drive very gently!

I'm sure you'll find lots of info in the archives or have a look at www.v8register.net or Paul Hunt's very useful site www.mgb-stuff.org.uk

Laurie Webb
75 BGT V8 Teal Blue
77 BGT 1950cc Flamenco
L Webb

What gearbox is best to use?
Dont really wanna hack to much of the car to bits!

Paul
Paul Elwell

The book, "How to give your MGB V8 Power" by Roger Williams is the best starting point for anyone.

cheers
Ian Buckley

Just bid on a copy from e-bay - thanks.
Just trying to get my head around a few things, any ideas on what box I can use?
Rough cost?

Cheers,

Paul
Paul Elwell

Paul

As you are going to Classic Car Show next weekend, look out for any MG related stands especially MGOC and MG Car Club, both of whom I know will be there and possibly the V8 Register boys (not sure if they will have a separate stand though as they are part of MG Car Club).

What year is your GT? Later rubber bumper cars (like my 77 Flamenco GT) shared the same body shell as the factory V8 anyway so the Rover/Buick V8 and beefed up MG 4 speed + o/d goes straight in. If you want the 5 speed option (Rover SD1 is the preferred option) some modification of the transmission tunnel is necessary. Costs for an SD1 box can vary from 50 on eBay for an unrebuilt (and untested!) unit to 1295 for a new one from MGOC. Factory V8 boxes are rare as hen's teeth and most sources will only rebuild your OWN unit for about 800 - so if you haven't got one in the first place.....

Enjoy the show on Sunday.

Laurie Webb
75 BGT V8 Teal Blue
77 BGT 1950cc Flamenco
L Webb

So if I re-built my box I can use it with the V8?
Looking forward to Sunday already!

Paul
Paul Elwell

Sorry, no Paul. I am referring to rebuilding ORIGINAL V8 boxes. The casing as well as the internals are stronger than an ordinary B box to handle the extra torque. People probably have used standard B boxes and no doubt someone will add to this thread saying they have had no problems but I am told by a local mg specialist who service factory/converted V8's and also convert B's for customers that even the proper factory V8 box has its weaknesses. I would strongly advise you to wait until you have your hands on the Roger Williams book and have spoken to V8 specialists at the Classic Car Show.

By the way, I checked out the feasability and costs of having my 77 GT converted to V8 power but decided that the better option was to buy a factory V8 for which I paid about the same as the conversion would have cost and I still have the 4 cyl GT to sell to recoup some cash to spend on getting the V8 into top condition. Obviously if you have time, cash and ability to do a home conversion you can produce something to suit your exact needs - such as a new spec 4.4litre block with high compression heads and fuel injection to give you 250+ bhp but quite frankly my standard 137bhp version leaves most modern cars as a disappearing speck in the rear view mirror! On a run down to Surrey the other week only a Porsche Turbo and a Mitsubishi GTO out accelerated me out of the roundabouts on the dual carriageways. OK, modern cars including turbo diesels overtook me on the M3 but they had to go WAY over the speed limit to do it and I value my 37 year clean driving licence!

Laurie Webb
L Webb

Thanks for your advice, will take your point on board.

Cheers,

Paul
Paul Elwell

The casing is different on a factory V8 box but I think that is more to do with interfacing to a different engine than strength. The internals are to the same design as the 4-cylinder, just different ratios of course. The box does indeed has its weaknesses, which also seems to indicate there were no specific strengthening changes made to it, as the engine was used with even higher power outputs in other models which *did* have stronger boxes. Shaft-stripping is one of the weaknesses, it was common to use a modified 4-cylinder shaft in its place as V8 ones weren't available for many years, I believe they may be now.
Paul Hunt

Paul,

The other point which has not been mentioned is that the transmission tunnel will have to be modified if you use the Sd1 box (or other LDV variants) or the uprated box used in the Jaguar and RV8 (380 box).

I had to weld in a wedge about 1" tall and 6" wide to accomodate the 5 speed box, it is much taller than the MG one.

Mike
Michael barnfather

Anyone got any pics of any mods they have done?
Know of a box for sale localy?

Paul
Paul Elwell

Paul,

Could try Terry Brown


http://uk.geocities.com/frc800uk/prices.html

or
http://www.gearboxman.co.uk/
Frontline for Ford

Also series of articles in Whats new! Supersports may be of interest

http://www.mgcars.org.uk/cgi-bin/gen5?runprog=mgoc&p=emg/mgbv8r.htm

Paul
Paul

Paul, I know of a good V8 SD1 box for sale complete with bell housing, you can email me or call 07005 947161 to discuss.

Charlie
charlie

Hi Gang,
I love Laurie's fix on the V8 question. Just buy one. The great pert of this story is that he has the 4 banger to "sell to recoup some of the cost of the V8" Did anyone else notice that he didn't say he actually did sell the 4 banger? Viola, now he has 2 MG's which appears to be the average number of these little cars owned per club member here in Minnesota.
Good show Laurie, and great advice to a fellow MG enthusiast!
Just for fun.
Chris
c l sorenson

Chris

My first two postings on this thread do indeed show me as the proud owner of TWO GT's and I would love to be able to keep both but garage space is very limited.

The 4 cyl GT has now been sold to a lovely Nigerian gentleman who sent me a cheque for TWICE the asking price so I can give the extra cash to his shipping agent!

Actually, no it's not sold yet but it's early days as I only bought the V8 less than three weeks ago. The 4 cyl (1950cc by the way!) has been outside my friendly local MG specialist for about ten days where a lot of people will see it as they drive past - which is exactly the way I found it 16 months ago!

Laurie Webb
75 BGT V8 Teal Blue
77 BGT 1950cc Flamenco (not for too much longer though)
L Webb

This thread was discussed between 18/10/2004 and 20/10/2004

MG MGB GT V8 Factory Originals Technical index

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