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MG MGA - MGA engine to MGB Gearbox, HELP!!!

Hello everyone, I am new to this site and I need help please. In a nutshell I bought a 1958 MGA 1500 in Florida and imported it to Barcelona where i live. It has an MGB engine and gearbox fitted which I think is a good modification. Unluckily for me the only way I can get it on Classic Spanish plates is to return the engine back to its original 1500cc, this was picked up by the Spanish technical engineer. So I ordered a totally rebuilt 1500cc MGA engine from a company in Scotland at it has just arrived here. I have removed the 1800cc engine and I have them both side by side on my bench. Now my problem is mating the 1500 engine to the MGB gearbox. So far I have attached the MGB back plate to the 1500 engine, blanked off the mechanical fuel pump and rev counter holes, as my MGA has both items electric. I realise now that I have to take the imput shaft out of the MGB gearbox and have it machined down to fit inside the 1500 crankshaft, also my MGB 127 tooth flywheel has a different hole alignment. Will an MGA flywheel fit so that I can use the MGB starter motor and clutch, or do I need to change it all? I am now wondering what is the most simple way forward, maybe change the gearbox too? What a pain in the butt the Spanish authorities have caused me, as the car ran fine before. One other question concerning the MGB back plate, I removed the oil seal to be able to get it over the end of crank fixing wheel, fitted a gasket and sealer between the engine and back plate and bolted it on. I read somewhere that the MGA does not have an oil seal in the back plate, so do you think this will work?
I welcome any help.
Thanks, Steve.
S Meredith

There are lots of MGA gearboxes around because of all the five speed conversions (another option to consider) so it might be easiest just to drop one of those in.

I think I would have been tempted to grind the "8" into a "5" on the side of the block and remove/change the engine plate!

If guys can get away with it in concours masterclass it should be good enough! No names!!!
N McGurk

As i have lived in Spain for 5 years i know how difficult the technical ITV test can be. How did they pick up it was the wrong engine? Can you not swap engine numbers over? Barneys site should give you some tips , its just most people fit a 1800 engine and not the other way around.
Roy
R Mcknight

Hi guys, thanks for your comments. I had thought about grinding off the 8 and making it into a 5, but I guess that i thought someone may have picked up on it seeing as the technical engineer had already taken photos of the massive 1800 on the side of the block. Roy, haven't you ever noticed the massive 2" 1500, 1600 or 1800 embossed figures on the front left hand side of the block. It wasn't the engine number that gave the game away as it was missing.
Thanks, Steve.
S Meredith

It is very unusual that anyone will mate a 3-main bearing engine to a 4-synchronzer gearbox, but the question does come up occasionally.

So you put the B engine back plate on the A engine to match the B gearbox bell housing. So far so good. It is true the A engine does not have a rubber seal at the back, but it (normally) does have a slut in the front side of the rear plate to allow drainage of any oil that sneaks past the rear scroll seal so it can dribble down the front of the plate without going into the bell housing. If you do this, you should grind the drain relief slot in the front of the rear plate.

127 tooth ring gear means you much have the larger post 1967 4-synchronizer gearbox (which must have been a pain to install in the MGA). So you can use all of the MGB parts from the rear plate back (including MGB clutch).

You have a few more problems left. As you noticed, the B box input shaft does not fit into the A engine spigot bushing. It is not that big a chore to disassemble the gearbox and have the input spigot turned down to suit. It will need to be 0.6230-inch diameter (0.002" undersize for oil clearance).

Alternatives to that modification would be boring out the spigot bushing nesting hole in the MGA crankshaft (requires engine disassembly). Or replacing the MGB gearbox with MGA gearbox (requires restoring the original rear mount on the frame as well as replacing engine rear plate, flywheel, clutch, and maybe the starter motor as well). Or replacing the late MGB gearbox with an early 3-synchronizer MGB gearbox (saves the modified frame mount but requires changing back plate, flywheel and maybe the starter motor).

Assuming you will modify the input shaft spigot diameter, you still need a flywheel that will mate to the 3-main bearing crankshaft. All of those (original ones) are smaller diameter (120 tooth ring gear). The engine rear plate that works with the starter position required for the smaller flywheel (pre-1968) does not work with the larger bell housing on the later gearbox. so you would have to make a special rear plate to mate small flywheel and starter to large bell housing.

A different alternative is to re-machine the later larger flywheel to fit the 3-main crankshaft. That would require enlarging the center pilot diameter and relocating bolt holes.

Bottom line is, it is fairly easy to mate a 5-main engine to a 3-synchro gearbox, but a royal pain the other way around.
Barney Gaylord

Hi Barney, Thank you very much for your advice. I think the way to go is to turn down the input spigot, fabricate a new back plate and fit a 120 tooth MGA flywheel as you said. I realise the starter motor position hole will need to be moved to suit the MGA flywheel but will the teeth on the 120 tooth flywheel will still mesh nicely with the MGB starter motor? . I have a good machine shop a few doors away from me here in Barcelona who can make the custom back plate and turn down the input spigot. Now all I need is an MGA flyweel from somewhere, ebay i guess?. Thanks very much, I can stop scratching my head now. I will let you know how i get on.
Steve.
Steve Meredith

Steve

You can have my 1500 flywheel when you are over in the UK next week. Avoid Wednesday, otherwise here all week. Why did the Scottish rebuilder not include one with the engine?

Steve
Steve Gyles

Hi Steve,
That's fantastic, thank you. I could collect it on Tuesday afternoon if that's okay with you? I will call you when I am in the UK to confirm a time. Look forward to seeing your new place and your MGA. I guess it would have been easier if the new engine had a flywheel though.
Steve.
Steve Meredith

This must be part of Spain's plan to get out of its financial black hole - reminds me of Australia during the Depression when they paid people to dig holes in Bondi Beach and then paid others to fill them back in - thankfully our transport authorities are much more enlightened these days!
Mike
Mike Ellsmore

Hi Steve , yes i know about the casting number on the block i just think its bad luck that the inspector found it . He was either lucky or he knew what he was looking for .
When i was in Spain i managed to register a 1275 frogeye fitted with 5 speed box . But there are plenty of unlucky expat enthusiasts in Spain who cannot register modified classics and still run on UK plates . Sometimes its easier to register your import in UK and then get it put on Spanish Historic plates after.
Or just find a friendly or blind technical inspector.
Years ago you could not even register a RHD car in Spain and you still cannot register a RHD van or Pickup truck .
EU harmony at its best .
R Mcknight

Steve

Can I ask who your rebuilder was? I have an early B engine that I may want rebuilding for the A. I live in Scotland but I am not aware of a local rebuilder.

Paul
Paul Dean

Paul, Some years ago I bought a recon. unleaded cylinder head from Cameron Gilmour in Errol,Perth who was also doing complete engines at the time....................Mike
m.j. moore

Hi Paul,
Strangely enough, Mike knows the same guy. It was Cameron Gilmour, his work is good and he's a nice guy too. Here is his website: www.camerongilmourengineservices.com
Steve.
Steve Meredith

This thread was discussed between 27/11/2012 and 28/11/2012

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