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MG MGB GT V8 Factory Originals Technical - has anyone done a rotary conversion?

i just bought a '71 mgb project car with the intention of swapping a 13b rotary engine (with turbo) into it and i'm wondering if anyone's done a rotary swap into an mgb and could give me any info. thanks.


jeff, never seen one in a b, not to say it hasn't been done, i have seen them in midgets in fact their are a couple sites for these conversion in a midget, send me your email address and i will send you the links for the sites, good luck, what horse power does that engine have, final drive ratio etc, just fyi, thnaks, jim
jim m

hi jim. thanks for the response. i've seen the sites with the rotary midgets. and they look pretty fun. as far as the engine is concerned, i'm not sure about the specs at the moment. i know that forced-induction 13b's have been cranked up as high 400 RWHP. so figure around 450 hp at the crank. i want to have good streetability on mine so i'm aiming for something around the 300 hp mark with a supercharger.

with all the v8 conversions done, are people finding that the car can handle 300 or more hp? i know the tranny and rear end have to be swapped. but i was more concerned about how large you could go with tires on aftermarket wheels and how the body in general handles such high power.

Three years or so ago, I had a '82 RX7 with a 12A and 5-speed transmission that I intended to put in my '73 Roadster. Actually mounting the engine in the car would not be too much of a problem because the Mazda engine uses an engine plate in the front with motor mounts on it--easily adaptable to the MG frame without welding anything. The problem (for me) was when I lowered the engine/trans into the B, I had to keep taking stuff off the engine to make it fit. The rotary is wide at the bottom and the exhaust ports are on the right hand side and would be pointing right next to the frame. Maybe the Midget is wider there or the frame kicks up (or something), but I wasn't willing to make the modifications that I saw as necessary to make this fit. Even tube headers wouldn't work. Now, I only spent a day's time looking at this, but I just couldn't see a way.

I went through the 4-cylinder with a freshen up and that's been good. Now, I've got the Ford 302 bug.

Wayne Pearson

There is a small article and photos (2 pages)of a 12A rotary into a '71 B roadster in the Jan/Feb 1999 issue of Grassroots Motorsports. Not a lot of detail in the photos but I can attempt to scan the article and forward it if you wish. Grassroots also installed a rotary in a Triumph Spitfire as a mag. project that looks great.

Phil, just for my own education, I would appreciate having a copy of the article.

Thanks in advance,
Wayne Pearson

phil, i would greatly appreciate that. i bought all the backorder issues of grm for the rotary spitfire. but i wasn't aware of anything at all being printed about a rotary mgb. thanks in advance.

I saw the rotory MGB that was in Grassroots at Import Carlisle (PA) a few years ago and again at Watkins Glen last year. The 12A looks like it was an easy fit - the only difference between the 12A and 13B is that the 13B is about 30mm longer (~1.25"). I would like to do a turbo 13B in my '70BGT when the 4 banger finally dies. It will be something to park next to my 13B Midget :)

BTW - some of the turbo motors have been dynoed at over 550hp
Brian Kraus

There was a MGB GT up here in Tacoma WA that had a Rotary in it. I only saw it once a good 6+mos ago. the owner was not a MG person, just stumbled on the car for a good deal. As I remember2mos ago he atended a meeting as was selling it, but I lost his information..
Larry Embrey

This thread was discussed between 30/04/2002 and 07/05/2002

MG MGB GT V8 Factory Originals Technical index

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