MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - 1800 in mga anyone?

Hi,

I am currently undertaking the restoration (slowly!) of an 1957 mga coupe. Whilst at the restoration stage I am considering putting an 1800 mgb five bearing unit into the car instead of the original 1500 unit. I have done quite a lot of research into this and I am intending to fit front disks, 5-speed sierra gearbox conversion and early mgb rear axle to complement this engine. (Also maybe a burgess or x-flow head at a later date if funds permit)

I was just wondering, as a 23 year old who has never driven the mga in its original form. What do you guys think of putting an 1800 into the ‘a (Sorry I’m sure this has been debated many times before!). I would be particularly interested in anyone’s experience of performing this type of conversion.

I have owned an mgb gt for a few years now and have reliably commuted to uni/work and toured Britain and Europe in it. I would like my mga to eventually take over the b’s mantle (probably not the commuting bit), but I would like one that is a bit quicker and better for touring/motorway driving than the original 1500.

I feel fitting the 1800 this the best way of realising that ideal without altering the character of the car too much. (or selling my soul to raise enough cash for a twin-cam!!!)

Cheers guys,

Ian
Ian

I've never driven a 1500, but my '58 has a 3-main 1800 engine. The power is more than adequate for the car. In fact, even being somewhat of a purist I would venture to say that it is the perfect engine for the car. The 3-main engines are said to rev more freely, and you won't have to change to a later-style electronic tachometer. You will also be creating more heat with any 1800 so be prepared to upgrade the radiator core and make sure the cooling system is in tip top shape.

Can't offer advise on the 5-speed as I prefer the original unit with a 3.9 rear end. I don't see the need for an MGB rear axle, they are nearly identical to the MGA unit. Just install the B's 3.9 gearing into the A pumpkin for better highway cruising and to take advantage of the additional horsepower of the 1800.

Here's a photo of my engine bay for reference:
http://www.lbcnuts.com/mg/mga/dscn1431.jpg
Steve Simmons

Ian
My 61 came with a decent 1500 in it. Nice engine but was a bit lacking going up hills with a passenger. Having had an MGB I knew the 1800 was the way to go. I came across a rebuilt 1800 3 main and I couldn't believe the difference. I kept the original tranny and have an MGB 3.9 rear end. For me it's a great combination. As Steve said the 5 main will require an electronic tach but you get the advantage of a rear main seal.
Kris
Kris Sorensen

Yep, you will find lots on this in the archives. I've been running an 1800 3-bearing, Sierra Five Speed and 3.9 rear end in my '56 MGA for about two years and I love the combination. Note that 3.9 MGB rear end...it really helps the cruise speed. Also consider converting to front disc brakes, electronic ignition, alternator and anti-sway bar. Great combination and all bolt-in tech, so it can all be converted back to original.
Frank Nocera

Ian once you throw purism out of the equation the MGA can become a very nice motor car. Naturally it is already but I should say can be made a lot nicer!
The 5 speed box is great and a lot smoother than the original, so that gets rid of a lot of mechanical noise.
I thought the 1600 was pretty good but if you want performance then obviously an 1800 is an easy modification My 1600 tours France each year and easily travels at 70MPH hour after hour without problem, although it did benefit from a 3.9 diff.
Bob (robert) I used to own a Morris Oxford

I have installed a 1868 CC MGB engine with a Peter Burgess fast road head and also a Ford Sierra 5 speed box. The difference is INECREDIBLE! I can cruise at 90+ (other parts of Europe) have fun and the confidence to overtake. Chris Bestson did all my work and will give you plenty of free advice: http://www.octarine-services.co.uk/ Definitely go for it - transforms the car completely.

John
J Harle

Ian

I have done exactly the same modification to you, including the front discs. It all works very well.

Like you, I installed the 5-bearing engine which means you will have to fit an electronic tacho from an MGB. One major tip that will save you a lot of heart ache is to fit the 1500 front plate on the 1800 block. This is correctly drilled for the engine mounting brackets.

Best of luck

Steve
Steve Gyles

i to am contemplating this same set up. will the original mga tranny bolt up to the 5 main? thanx for the tip on the front plate!

mark
Mark Youden

Hey Ian,

Being of the same age as you, I also consider installing a 1800 engine in our 1500. I love to drive the 1600, but getting out of a modern car it feels sort of sluggish.

Just wondering, don't you guys think a 3.9 rear takes the sportscar bit out of the MGA? I am thinking of using a 3 main 1800 in combination with a 4.1 ratio axle. Any experiences?

Regards,
Koen
Koen Struijk

Here in LA, the highway speeds are very high, sometimes 90MPH or higher. I need the 3.9 just to keep up. The gearing in the stock transmission is very low anyway so acceleration is more than adequate.
Steve Simmons

G'day I have a 1500 4speed still in my 59 coupe & yes its a bit slugish up hills but still quite reasonable on the flat.Imho you don't need the 5 speed as well unless you are doing a lot of touring.We drive to Brisbane (80mile each way)in our 66 B 1800 4speed a fair bit and it handles it well. Bob
B WALKER

sorry if you do your swap sell me your 1500 Bob
B WALKER

Cheers guys,

Just a couple more questions.

I have a spare mgb gt rear axle, can this be used or is it only the earlier banjo style unit that can be used? And is it possible to convert this b axle to wires?

Also has anybody fitted a 'B' overdrive gearbox instead of the standard 'A' four speed unit? I am worried that the standard transmission will struggle with increased power from a mildly tuned 1800 unit?

Ian
Ian

Fitting the standard non-synchro 'B gearbox into the 'A is doable, but a bit of work - not just a bolt-in; I considered doing this and Barney Gaylord talked me out of it (check his website - he used to, and may still, have a copy ouf our correspondence on the matter). Check the position of the starter motor too.
The OD box is bigger in the rear and I think would probably require modifications to the transmission tunnel to fit, in addition to the considerations mentioned by Barney. The Sierra 5-speed conversion kits are probably better bets than the OD vis-a-vis fitting.

Regarding the engine: if I had to do it over again, I would opt for a 3-main 1800 over the overbored (+.040, 1600 pistons) 1500 I now have. (Because there's no replacement for displacement - and you can still overbore the 1800!)

I think you can use the BGT rear axle. I believe you can convert the axle to wire wheels by changing the hubs but you may have fender well fit problems if you do so; the wire wheel banjo axles are narrower than the disc wheel units and I'm guessing that the GT axles would be too. It has to do with allowing for wheel offset differences between the wire and disc wheels. There is more specific info about this subject in the archives.

Good luck with the project.
Marvin Deupree

MGB wire wheel axles are plentiful and cheap. It would be better to go that route. The bolt-on wheel axle housing is more narrow than the wire wheel housing, so you would have to cut down the axle shafts, etc to make it work. The other option is bolt-on wire wheels but you won't fool anyone who knows anything about British cars!

I've seen photos of an A with a 3-sync OD transmission and I would kill to have that in my car. However I am not willing to hammer out the transmission tunnel to accept it. I only perform completely reversable modifications on my cars.
Steve Simmons

The 57 A I used to have came to me with a 1950cc 1800 3-main MGB GA engine already in it, work done by the friend I bought it from. It used a the MGA transmission and other than the greater heat generated as Steve says, I had no real problems, and probably a bit more fun with the car than had it remained stock. It seemed a very nice combination, and on cross country trips it performed very well and almost effortlessly even across some of the steepest passes over the Rockies. I once had a fellow follow me in his MGC from the NAMGAR GT at Lake Tahoe to the National car museum in Reno. I had barely stepped out of the car when he came up to me and wanted to know what I had done to the car as he was not used to early MGAs being able to keep up with him, much less never give him any quarter to pass. At the time, I hadn't realized that the car was performing that well, but again, as Steve says, it certainly seems to have been a combination designed in heaven for the MGA.
Bob Muenchausen

Koen,

3.9 Diff with MGB 14" wheels comes about about the same as 4.1 diff with MGA 15" wheels.
Not sure the Smiths part number, but you wold need to change your speedo or change the cog inside it, but even then with modern tyres it will still be way out.

So with 1 to 1 (4 speed) gearbox you should get about the same top end speed.

You can use the gear calculator on the twin cam site, but that's setup for standard tyres though.

I run 1860 Stage 6+, 4 speed and 4.1 LSD on the MKII great all round fun.

Cheers <MARK>
Mark Hester

Couple of points (done this many times).

You can use an MGA rear engine plate if you wasnt to keep your trans. Remember that you'd have to have it machined to take the rear main seal if you are using a 5 main engine.

If you are switching to a diaphragm clutch (good idea), you can keep your driven plate but must use the front trans plate with throw-out arm fulcrum and the throw-out arm itself from an MGB (different height).

Be aware that some of the early MGA boxes have insufficient clearance in the bellhousing for the diaphragm cover - if you bolt the engine to the trans and the engine no longer turns over, that's a pretty good clue that you have that situation. All is not lost - unbolt it until it just turns over, and then turn it over a few times (you are marking the high spots in the bellhousing). Relieve these spots with a grinder and you should be all set.
Bill Spohn

Don't get my mates at Brown and Gammon to do the machining of the backplate though.
I nearly took those clowns to court over my mess.
They will tell you they know it all. I now know otherwise.
Sorry not may people wind me up like they managed too.
I should have just bought one for £130 ish from the 5 speed people.

I found the MGB clutch forks hard to get though.

I went for MGB 4 hole layshaft MKi gearbox and then fitted the MGA rear housing to it, so I didn't have to change the gearbox mounts on our other MGA.
Those boxes are £50 from or less from there as everyone wants O/D
http://www.mgbreakers.com/MGB.html#Transmission

Then you don't need to play the backplate and starter position game.

Cheers <MARK>
Mark Hester

Hi Ian,
Two years ago I installed a 1974 5 main MGB engine into my '58 MGA. I had two 3 main engines both needing machine work so I decided on the 5 main 040. over, fast road cam, mildly polished stock MGB cyl. head, and the stock MGA trans. I did install a 3.9 ratio rear out of an early "B". Quite an improvement over the old 1500 engine. Had this car out to several events over the last two years and everything works perfectly. I would highly recommedn the conversion as it makes one of MG's sleekest looking cars perform as they should have many years ago. some minor fitting problems but nothing very serious.

Good luck,

Roy D.
Roy Dougherty

This thread was discussed between 02/01/2006 and 03/01/2006

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.