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MG Midget and Sprite Technical - K Series engine - gearbox options?

Hi

A question for the K Series engine swap gurus on here please:

What are the options for gearboxes for K Series engines in rwd applications - I understand there are bellhousings for Ford Type 9 gearboxes/Caterham 6 speed, what about for lighter 4 speed Ford gearboxes such as Type E (‘Rocket’), 2000E/Bullet as well as Type 3 and 2? My knowledge of Ford gearboxes is limited.

Don’t laugh - I am thinking of an 1100cc K Series (K8) single cam with its standard single SU carb and distributor from a 1995-1998 Rover 100 (Metro) to go into a Locost 7 project. They also did a 1.4 in the same spec. No ECU and perhaps no cat. I could upgrade to 1400cc etc twin cam and ECU later if I fancied.

Sort of a Locost take on the Coventry Climax 1100 that went into early Lotus Sevens. If the gearing is OK, be made so via a BGH first gear swap, then I would prefer a lighter 4 speed than the heavier Type 9.

A spare 948cc Sprite engine still might be an option, bored out with oversized 998 Mini pistons.

Cheers
Mike
M Wood

Do you realise that the 1100 K series is actually 1129 cc, so no use if you need it in a sub 1100 class. It has a 75 mm bore and a very short stroke. The cams are low lift short period too (7.8 mm x 232 deg ?, I think) in an attempt to get some bottom end torque. It does spin well though. The 1.4 8 Valve is a much more satisfactory engine. (9mm x 240 deg MSW cams). I know someone who put a 16v head on a 1100 bottom end with mechanical tappets. It revved to over 9000 rpm.
Paul Hollingworth

Would a Suzuki Jimny box fit. Barratt Engineering sell a kit for an A Series engine. A MX5 could be another option. Both the boxes are made by a Japanese firm and are streets ahead of a type 9 for quality and innovation.


Jan T
J Targosz

I don't think there is many options bar the type 9 box. Although if the 2000E boxes are the same bolt pattern as the type 9 then I suppose any Ford box will fit.

I contacted a guy who makes adaptor plate for the MX5 gearbox, to mate a various engines. There was no desire for a K series plate tho so they don't make one.

Tarquin

The distributor sticks out of the back of the engine so you might have to cut away more of the battery tray.
I did enquire with James of Barratt Engineering whether they were planning to make a kit to put the Suzuki gearbox onto the K series. James said that it could be done but he needed a K series block to 3d scan it into his system. I think one of the problems he will encounter is mounting the gearbox a few inches back due to the length of the k series block. It might mean cutting into the cross member, not as drastically as for a type 9, but it will need cutting for clearance.
Rob
MG Moneypit

We used a Supra W58 box, but that is less relevant than how we did it.
We retained a K series bellhousing (Rover 200 with the final drive cut off) and made our own adaptor plate between bellhousing and box. Centering it was very easy - turned up a locating ring to fit the release bearing tube on the inside of the ring and the hole in the back of the bellhousing on the outside.

Using this method it is relatively easy to make a one-off adaptor plate, so opening up to using any gearbox with a bolt-on bellhousing.
It also allowed the use and position of the K series starter, thus shifting it away from the manifold heat. However the battery tray had to be removed. Structurally we have found no issues from that in the 20 years since we did it.

The Rover bellhousing is only 4" long, which allowed us to get a gear lever position in the same place as the original A series. An MGF one is an option but is 5" long.

There was of course a bit of welding needed to close off the post-amputation wound where the final drive was.

I can post pics if interested.

The W58 box is a bulky one which needed a lot of surgey on the tunnel so I wouldnt recommend it unless aiming at big hp as we were. (Ultimately the surgery resulted in a much stronger tunnel and more torsional rigidity in the body shell, but it was quite a bit of work.)

Paul Walbran

Jut a general question about adapting different engines and gearboxes; whether via the engine or gearbox end of the bellhousing...

If the adaptor is 1cm thick, doesn't that push the splined drive from the gearbox 1cm further away from the clutch? That's assuming that the gearbox to engine flywheel distance is correct in the first place. How do you pull the distance back the 1cm?



P Peters

All part of the fun - if money is no object then you line up engine and gearbox then design and build a custom bellhousing to suit complete with starter mounting and your choice of clutch mechanism.

If not then you start with what you have and iterate to find path of least resistance. Pauls approach above gets you over halfway, rest depends on what machining facilities you have - with a mill and a TIG welder almost anything can be adapted to suit.

Period conversions were usually done with whatever was cheap and available, seventies and eighties cars were fantastic for rusting away and leaving a ready supply of bits in local scrapyards to browse through until something doable was located.

With A series midgets I always wonder why 1500 gearbox + spitfire overdrive didn't happen, guess something must have been too awkward or expensive.
AdrianR

P Peters, yes exactly right about pushing it 1cm further back. But a different bellhousing is likely to be different in length from the original so everything needs calculating.
In our case, the very short Rover bellhousing meant we had to shorten the first motion shaft, and sort a spigot arrangement. Wasnt difficult.
The Rover bellhousing made the clutch easy too, used K series cover and bearing, and off the shelf plate same OD with splines to match the gbox
Paul Walbran

I don't know how I missed this first time round but:

--Paul Hollingworth
[...] I know someone who put a 16v head on a 1100 bottom end with mechanical tappets. It revved to over 9000 rpm.

Can you tell us more about this please? Sounds fascinating - what was the reasoning for this - was it a racing class limitation?

Apart from the 9000 rpm limit - which is probably reason enough! - what were the characteristics of the engine? Seems a lot easier and cheaper to stick in a standard 1.4 so I'm hoping there's some magic in the mix and match formula.

P Peters

This thread was discussed between 10/04/2023 and 18/05/2023

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