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MG MGB Technical - Light engine / gear box

I'm looking for a light engine and gear box replacement for my MBG project. It has to be at least 100 kilos lighter than the original stuff. Preferably a bit more powerful too, but this is not the major issue. I hope to avoid doing to much change on the body, and to be able to use the original MGB hood.

Suggestions?

Thanks in advance,
Tor
Tor

W*nkel rotary engine.
Chris at Octarine Services

Someone has put a rotary into a midget before:

http://hometown.aol.com/ursnoozin/myhomepage/auto.html

Simon Jansen

Ugh! Just about any modern 4-cylinder engine is lighter and more powerful than the B-series. Heck, most v-6 engines are too and a 60-degree bank v should be able to clear headers OK. You may need to do some fancy tilting with custom oil sump and mounts to make an OHC 4-banger work but it should come out OK.
Not many transmissions lighter than the MG unit (once you include the bell-housing) but once you are comparing OD vs real 5-speed then the later stuff is lighter again.

Mike!
mike!

There is of course the K-series conversion. Take a look over on the midget K-series forum. 1.8 turbocharged engine, all alloy...
Dave

Anyone have good links/info on the Miata swap? I've been unable to find anything in the archives and the only website I've found is for Eclectic Motors.
Tony

Hi Tor,

Nice to see another Norwegian on the board for once. Almost the same name, too!

How about an Alfa Romeo Giulia or 1750 engine/gearbox? All aluminium - must be a lot lighter, and with 5 speed transmission!

Tore
Tore

100 kilos is going to be hard to reach. Even with aluminum blocks and heads it will be tough. The aluminum block for my V6 only saves 47 pounds or about 20 kilos over the cast iron block IIRC. The GM 60 degree V6 is lighter than the B 1800 even with the iron block, but not by this much. The same for the Rover V8. Modern OHC engines are tough to fit under the bonnet because of the additional height of the cams and covers. The Miata will fit in the B pretty well, don't know about the weight though. It will have to be all aluminum to even come close to meeting your weight target, that limits things a bit also. Mazda rotary would probably be closest.
Bill Young

So far, the rotary engine is the only option that I know is light enough. I saw somewhere that the Mazda 13B is 220 pounds lighter than the MGB engine. (I must admit that it feels a bit odd to put Mazda parts in my MG).

Does anyone know the weight of the MGB engine - or of any of the other options?

If I go for the 13B engine - should I use a RX7 gear box? Would the MGB gear box fit?

I don't know much about the rotary engines. Are there any major disadvantages? Do they sound OK for a classic British car? Any other issues to concider?

Tor
Tor

Sound is completely different from any 4 cylinder engine, more like a high reving 6 cylinder as the rotary has two three lobe compressors. Most people doing engine swaps would advise to use the transmission that mates to the engine if possible, as this saves a lot of fabrication time and utilizes no special built parts which will require replacement in the future, (clutch assembly). Additionally these transmissions are rated for the power and torque of the engine so you don't have to worry about weak links in the drive train. The B rear axle should be strong enough, but is limited in ratio selection. If you are using the RX7 package check what that axle ratio is, it's usually a better match for the engine/trans torque curve and gear ratios if similar diameter tires are used. Be aware that the Madza rotary has the intake and exhaust manifolds on the right side of the engine and these can interfere with the footwell unless the engine is moved forward which may cause a poor location for the shift lever. Spending a few hours at the breakers with a tape measure will save you dozens of hours and many dollars in the long run on an engine swap. (Hint: a piece of wood marked in inches or centimeters and a couple of pieces of string with some old nuts attached will help measure engine length and width dimensions while installed in a chassis. Use the strings as plumb bobs and move one down the wood until they hang at the points you want to measure.)
Bill Young

Bill,

Some excellent tips for junk yard scrounging. Thanks! Another possible tip is to take a pair of carpenter's squares with you. Slip them together like a pair of calipers, and you can get some good width measurements.

Tor,

A complete MGB engine weighs 400 pounds. If you'll send me your e-mail address, I'll send you a picure of one hanging from an industrial scale, with the needle just nudging the 400 pound mark, maybe only 397/398. With a standard MG transmission, about 466/467. Add another 30 pounds or so far an overdrive unit.

A rotory engine will fit nicely in an MGB, as I have seen it done. I have no details or photos, but I did get a good look at an MGB/Rotory swap at a car show in Michigan a couple of years ago.
Dan Masters

I put an 86' Mazda 2liter mated with a Mazda 5 speed transmission into my 76' MGB. I only had to relocate the engine mounts. Even the stick shift ended up in the right spot. The engine I used is completely stock, other except for a 32/36 downdraft weber instead of the orginal feedback. It has an overhead cam, but only eight valves, so only a small power gain. I do get more than 35 mpg though. Mazda built this same engine offered with turbo, a 12 valved head and fuel injection. . My measurements show that the later 2.2litre engine would also fit with no clearance problems.

As for the weight difference, I have never been able to determine the weight of the Mazda drivetrain, but I did install shorter front coils to bring my front end to proper height.
mark guier

The rotary has interference problems with the front crossmenber and the frame near where the steering enters the rack. This swap is easier with a midget because the frame does not narrow at this point.

Pete
Pete

This thread was discussed between 25/08/2004 and 28/08/2004

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