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MG MGB Technical - A series head on a B lower block?

right i have found someone who says the heads are the same on a b series and a a series?

is this true? im sure its not- they are totally different sizes- if it is im getting a metro turbo head and charger!!! please say im wrong !!!!

SGE Granville

Yes you are wrong!
John Turner (Midget & MGB)

Brilliant i would have not gone to the extent of buying a stage head if i could get a metro turbo top end- speaking of which i am trying to hunt down a single weber downdraft inlet. Does anyone have one? Or does anyone who where i can get one on the cheap? Please no mention of ebay i have constantly been
SGE Granville

What about if the a series head is from a 1600cc? im sure it is still not going to fit onto a b series of 1978.
SGE Granville

I believe that your mistake lies in thinking that A-Series means MGA. MGA heads will certainly fit, since they, too are B-Series engines, like some years of the Nash Metropolitan, etc. A-Series engines are what were used in Moprris Minors, all Sprites, pre-1975 MG midgets, ad a host of other vehicles, including the Metro. The head from an MGA will fit an 1800cc MGB engine, but the one from an MG Metro or any other A-Series engine will NOT.
David "Midget owner" Lieb
David Lieb

Also, no A-series engine was ever bigger than 1275cc from the factory, although many have been bored out to 1340cc later. Thinking about that, isn't it remarkable? The A-series started life as 803cc. Amazing it can go out to 1340cc.
Mike Howlett

Hey, Triumph managed to go from 800 and some cc to 1500cc with the Spitfire engine. And Chevrolet's classic small block V8 started at 265CID and peaked at 402CID. You have to think there was some significant weight loss involved.
David "Credit where credit is due" Lieb
David Lieb

Troubles with the "A" series really started when they went to 1275 from 1100. To get the diameter they staggered the bores. Due to the shape of some of the castings the bore distorts when the block heats up, with the result that they burn oil. A lot.. (like less than 100 miles to a pint)

Some do, some don't.

If you have one that doesn't, keep it forever!
If you have one that does, no amount of reboring, or fancy pistons with extra oil control rings will help.

Martin Layton

This thread was discussed between 05/11/2007 and 06/11/2007

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