austin healy spright/mg midget

[peteskegness]

i have a 1971 austin healy spright and would like to fit one of 2 engine and gearbox the first being a ford 2.0 twincam from a sierra , the second is a mazda x5 1.8 unit and 5 speed box has anyone got any ideas on the above cheers help ....pete

[Samcat]

Hi,

Try posting your question on here: http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgb...

There is a great ammount of technical knowledge knocking around on this site.


Tim.

[Mr2Mike]

Of those two go for the Mazda lump every single time, there is simply no competition. It's a lovely little engine, revvy, reasonably small and light with a slick gearbox and lots of aftermarket support. You can even buy a supercharger or turbocharger kit to bolt straight on if you fancy more power.

The Sierra 8v DOHC is dinosaur by comparison. Heavy and large with a very 'relaxed' power delivery, almost no aftermarket support and parts are expensive. The MT75 box that it's likely bolted to is also a hefty sized thing to get into a Spridget transmission tunnel. It could be replaced with a Type 9 if you can find a decent one but they have very poor ratios for a light car in standard form, and are pretty heavy.

If you want a cheap, modern(ish) and reasonably light Ford engine then the 1.8 or 2.0 Zetec E is the sensible choice, but you are still limited to the same gearboxes. Alternative ratios for the Type 9 are available (from e.g. BGH Geartech), but don't come cheap.

[SB - Nigel]

Mr2Mike said:

It could be replaced with a Type 9 if you can find a decent one but they have very poor ratios for a light car in standard form, and are pretty heavy.

Unless you want a car for track use the Type 9 box isn't that bad ratios not far out from original Spridget box and usefully low geared for hill starts when the car is fully ladened (two faties and luggage) and touring use

[Mr2Mike]

SB - Nigel said:

Mr2Mike said:

It could be replaced with a Type 9 if you can find a decent one but they have very poor ratios for a light car in standard form, and are pretty heavy.

Unless you want a car for track use the Type 9 box isn't that bad ratios not far out from original Spridget box and usefully low geared for hill starts when the car is fully ladened (two faties and luggage) and touring use

For pairing to a standard A series engine perhaps, but as part of an engine upgrade package I have to disagree.

The standard 1275 Sprite 1st gear ratio is 3.2:1, which is low enough for the 65bhp/72lbft lump to pull a fully laden car up a steep hill. With e.g. the 2 litre DOHC Sierra engine fitted you have 123bhp/128lbft (nearly 80% more torque), and yet you end up with a first gear ratio of 3.65:1 with the short shaft Type 9. The V6 Type 9 is a little better with 3.36:1 first, but still lower than the standard Sprite box.

A lot of Lotus 7 style cars use the Type 9, with the heavier of these not weighing much less than a Sprite (maybe 600kg or so) and in these cars first gear in a standard type 9 is virtually useless for general road use, effectively transforming the Type 9 into a 4 speed box. There has to be a reason companies like BGH exist!

[kbigtim]

I don't see the point in sticking an MX5 engine in a spridget why not buy a decent MX5?
The K series + type 9 is the way to go.

[SB - Nigel]

Mr2Mike said:

What Mr2Mike said

sorry, whoops, didn't mean to post that as it was - I got interrupted then had to go out

I agree with you, I was going to say Type 9 with the A-series not so much for OP but others reading

getting g/box and back end ratio right with mating components from various other cars is awkward and because of there relative low volume most classic (British at least) production sports cars have compromise gearboxes

Certain mine and a friend's Type 9 boxes are not as nice to use as the old Spridget boxes but of course are not as worn out and benefit from synchro on first (not a problem so much on the Spridget boxes when not worn out) and really worth while you gain fifth gear

The bits between the engine and back axle also feel much more direct and smoother and firmer

Careful how you go with what you change the car too or you could spoil its character and I agree if OP is thinking of MX-5 engine and/or g/box then buy a MX-5

oops done it again typed so slow wife now waiting again