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MG MGB GT V8 Factory Originals Technical - 4-Cyl conversions

I have monitored this thread off and on for a short while and would like to know if anyone has done anything with modern 4-cylinder conversions. I was thinking of a GM Quad-4 with 5-speed. I am familiar with it's shortcomings but it could make for an interesting ride.

I'm not into brute power and the associated speeding tickets, gas milage, etc. Not to mention my reactions aren't what they used to be.

It would seem to me a 4-banger would retain the panache while adding a respectable amount of power and reliability. Since anything I did would be subject to long summer drives in the rockies, a reliable drivetrain is essential.

Are there any other 4-cyl engine conversions with a good track record? Any experience with weight & balance with these engines?
TJ Vessely

A friend is sticking a 160 BHP Nissan 240SX engine in his TR3 - it would work well in an MG as well. There are any number of very nice high tech 4 cylinders with more power than the old tech 215, for instance (though less torque, of course).
Bill Spohn

I drive a 19993 240SX every day. it ha one HECK of an engine. I've thought of putting one in a B as well. The 180BHP and 200+ #ft of torque from a 3.4 Camaro engine wins out.

V8 Archie of Fiero V8 fame is tearing apart a new Pontiac Solstice with the aim of making V8 conversion kits for them (What else..). The 2.4L Ecotec engine would make a nice MGB conversion... if you could figure out how to make it run...


We've got a slow-moving shop project of a Miata-powered MGB/GT. It runs and drives but needs glass and interior--hopefully this spring:

Carl Heideman

I would be embarrassed to own the 100 hp V8 tested in the last html.
Jim Stuart

Thanks for the informative feedback.

With these various engines, what happens to the front/rear weight ratio? I would venture some of the new engines are pretty light. Is respringing a necessity? Carl, The BGT is beautiful!

I have had a love for MG's since the 50's. Owned an "A" in the 60's (pre-kids). I have a TD spotted but by the time I can convince the owner to sell it and then spend the time getting it out of the basket and on the road, I could be back in diapers

I am still not sure which way to go as I am at that point in my life where I don't want to spend the next ten years working on a car and not driving it. After 3 kids and 12 consecutive years of college ($$$), A big investment is not realistic either. What ever I do I want to drive it. There are just too many beautiful mountain roads............
TJ Vessely

TJ...You may want to consider purchsing an MG that has already been converted! There are both V6 and V8's for sale out there! You can then be on the road and having fun for *most likely* fewer dollars and personal time invested in doing your own conversion!


rick ingram

Currently for sale on eBay:
Dana Wilson

1967 GT rebuild 2.8 V6 less than 1000 miles on the engine, performance cam, T5 trans, coil over front suspension, Wilwood brakes, power windows, power door locks and 4 ink rear suspension, plus more.

Will be for sale this summer.
Bill Guzman


I saw one with a 1980-Volvo B21A-sohc., 4sp+OD (M45, M46). It is easy to find, cheap, and the engine is extremely reliable. It had SU-carb set-up still in production in 1983. If a good B21a is rare you just have to find a B23F or B230(to-95) and bolt-on intake from a carburetter model engine. It will yield up to 125 HP with a carb. Another interesting aspect: Volvo gearbox with same OD found in MGB share also same U-joint(precision 341 for 13/4" driveshaft)) than MGB.

I have owned Volvos for many years and this engine last, last and last forever.

Your MGB will perform well with that 50% more power and this tranformation will not be irreversible and will not stress other mechanical components.


Jean Guy Catford

One bit of advice on selecting an engine for a conversion. Unless you have a great deal of experience with electrical matters or know that there is a 'kit' to adapt the computer controlled fuel injection and timing systems for that engine you would probably be better served to select an engine design which has been in production long enough to have earlier versions with standard distributors and carburation. Getting a later ECM engine to perform correctly without a special computer and remapping is difficult. Not the least of the problems is trying to figure out which input sensors are required and which my be deleted for proper operation.
Bill Young

The ultimate 4 has got to be the Fontana 4, which is an all aluminum version of the Mercruiser(?) which is a close relative to the Chevy II 153ci 4. Around 186 cubic inches I think. A little pricey tho, at around 17,000!!
Jack Morris

I've seen a SR20DET motor stuffed into a Japanese MGB. These four bangers make big power, with bolt on turbos available. The came in Nissan Sentra SE-R's and are what all the 240 SX guys (came with a KA24 truck motor) swap to.

I have a good friend putting a honda S2000 motor into his series 1 Ford Cortina. That will definitly be a rocket, but you haved to find a cheap wrecked S2000 to make it at all affordable.

I'm thinking of doing a Ford Focus SVT zetec motor myself.
Bill Mertz

The DVD Ultimate MG Performance:-

includes a great 250 bhp Hond S200 engined MGA with the Honda 6 speed 'box.

A great car & a great DVD (it also features my B GT V8)

Have a look at the trailer:-

Nigel Steward

JGC, The Volvo idea sounds interesting! Worth looking into, I think. Volvos of that vintage should be available at reasonable prices.

Jack, Where can I find more info on the Fontana 4?
Tried to Google it but couldn't find anything. Out of my range but sounds interesting. I have been out of things automotive for a while.

Thanks everybody for the information. I think There is more good info on this BBS, than any of the others I've ever tried!

There are a couple GM3.x V-6, 5-spd MG's around here. This seems to be a good match but,,,,,,,,,,,,,,,,,,,,,,

I'm Definitely stuck on the idea of a 4-cyl. Probably goes way back to my younger days of hearing a well tuned MGA with an Abarth exhaust system being pushed to the limits through the turns at Indianapolis Raceway Park. That's a sound that makes it all worth it! Yes I was driving. No it wasn't mine!

Again, Thanks everybody


TJ Vessely

TJ, could be a bit pricy for you, but have you considered using the B 1800 with a cross flow head and a Nissan 5 speed? That would give you plenty of power, good drivability and the sound you are looking for. Probably cost around 4K to get it all installed and sorted out. Some swaps would be cheaper, but not by much.
Bill Young

One more addition: In the late 70's (I think) there was a fad with midget racers running half of a Chevy V-8; there were inline slant 4's and V-4's!! They were radical and made awesome horsepower. There was an outfit up north somewhere that had a nice business sawing them in half whichever way you wanted them. I've wondered a lot if they're still around.
Jack Morris

A couple of other 4 cylinder options are the 2.2/2.5 L. Dodge turbo motors. There are thousands of them out there and they can make large amounts of horsepower cheaply. Then there is the turbo 4 in the 80's Thunderbird. It has IRS as well.
Phil O


Another option is a Mustang 2,3L-5SP. with an Holley carb. That german based engine is strong and easy to upgrade.


Jean Guy Catford

were can i find a b21a not a b21a1 the japan one b21a its only like 7 to 10 more horse but i think it would be cool to but in my 3rg gen

No idea if you can fit it in, but the Eagle Talon turbo motors (Mitsubishi) can be modded to put out 350 - 400 BHP pretty reliably.......
Bill Spohn

Have you consider a Ford V8 ro Chevy V6? they are only 2 or 4 more cylinders!
Steve Bacon


What motor are you talking about. A b21a1 is a Honda prelude engine as far as I know and it is a hi-rev. type and non-torquey. A B21A is a Volvo engine in 240 models.

Jean Guy Catford

This thread was discussed between 14/01/2006 and 02/02/2006

MG MGB GT V8 Factory Originals Technical index

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