14 replies to this topic

[ollydc5]

Hi guys and girls, me and my Dad are looking at a replacement engine and gearbox for our new mini.

I'm quite new to this mini game but I'll give you a run down what we'd like. The car will be used for a bit of road but I'll prob do a few small track circuits and sprints just for fun with friends.

Not sure what's achievable but would like about 80bhp out of the engine.

Was looking at a stage 2 1293cc from mini sport or somewhere, wasn't sure if I'd get one second hand. Comes with everything needed block and head, my Dad wants to put twin carbs on.

As for the gearbox we were going with a straight cut kit, helical lsd and maybe a 4.1 final drive.

I want the car to be quite punchy but not knowing these cars I'm not sure whether it will drive like a bag of spanners. Clutch unknown yet, will be using semi slicks to aid traction.

Any advice would be much appreciated:-)

[robminibcy]

4.1 is a very high final drive, your cruising revs will be very high, id be looking more at 3.7 or 3.4 for a road car which will still have quick acceleration with more top end.

[carbon]

Hope Minisport have got better. Last dealt with them 20 years back, they sold me duff gearbox parts and would not accept liability or replace.

 

Never used them since.

[ollydc5]

Thanks for the feedback, what is the top speed of a mini using a 3.7 final drive ? That's a shame about mini sport, are there any well rapid places to shop for engines and parts ?

[carbon]

Top speed will depend on lot of factors.

 

As a guide the original Cooper S with nominal 76bhp did just under the ton (2 way average on road tests) on a 3.65 diff.

 

If you have a well tuned 1293 fast road motor then you may get 5-10 mph more average top speed, but on a 3.76 diff engine will probably be spinning at well over 7,000rpm.

[Cooperman]

A 4.1 is, in fact, very low and will give around 12.5 mph per 1000 rpm in top gear. Far too low unless you can rev to around 7500+ rpm with peak power at 6500 rpm or higher. That is race engine territory really. With that 6000 rpm will be just over 75 mph.

 

I too have had issues with Mini Sport many years ago. For your engine work I recommend Rob Walker Ltd of Witney, near Oxford. Top quality at sensible prices.

 

An LSD for the road is really horrible to drive, so try to drive another car with one in before you finally decide. Probably only worth it for an out-and-out race car with around 125+ bhp revving to 8000 rpm.

 

Be advised to read David Vizard's book 'Tuning the A-Series Engine' before proceeding to spend a lot of cash.

[Tupers]

You shouldn't need a straight cut box or LSD for the power you're looking to make. A Mini Spares cross pin diff and an "S" ratio gear kit in a rebuilt box should be more than up to the job a much nice to drive with. 

 

As said above it's well worth getting yourself a copy of Vizard's book. 

[Alex_B]

I am currently in the process of planning and building a new engine for mine. Going with a SC 16v head so will be making more power than your planned engine, I am using a straight cut box and x-pin diff in mine along with likely a 4.1 ratio final drive. This is due to me wanting to use my mini for motorsport (Hillclimbing). 

However I am considering building it for the road and building a hill climber at a later date, if so I will be using a lower final drive. With a 4.1 ratio diff you are pulling 5500 rpm at 70 mph which is less than ideal for motorway miles.

[ollydc5]

Many thanks for the input.

I'm used to doing these kind of mods but in larger cars, I think I may just aim to get the engine first with just the gear set and then see how I go. It will be driven on the road but as far as the motorway it'll be maybe once a year.

Didn't realise that the 4.1 would limit it to such a low speed, have got to get it in my head that it's a mini. Far to clueless at the moment lol

I'll take it on board though guys many thanks,

[ollydc5]

Ps my Dad has the Vizard bible lol, will have a read over the next few weeks

Will also check out the engine builder as mentioned many thanks

[Tupers]

Once you've figured out what cam you want and where it's power band is the raito calculator on Guessworks is very handy for figuring out a good final drive. Clicky

[Bubblebobble]

A 4.1 is, in fact, very low and will give around 12.5 mph per 1000 rpm in top gear. Far too low unless you can rev to around 7500+ rpm with peak power at 6500 rpm or higher. That is race engine territory really. With that 6000 rpm will be just over 75 mph.

 

I too have had issues with Mini Sport many years ago. For your engine work I recommend Rob Walker Ltd of Witney, near Oxford. Top quality at sensible prices.

 

An LSD for the road is really horrible to drive, so try to drive another car with one in before you finally decide. Probably only worth it for an out-and-out race car with around 125+ bhp revving to 8000 rpm.

 

Be advised to read David Vizard's book 'Tuning the A-Series Engine' before proceeding to spend a lot of cash.

Never new that place was in Oxfordshire ! Excellent as usual Cooperman !

[mini13]

Have to agree, Rob Walker is good and good prices too, plus a really nice chap too!

[Fast Ivan]

80 bhp is fairly easy to achieve and there are a few A series specialists out there who could do it for you and you can be confident that your engine will be fine, minisport don't have this reputation

but it will cost.....

 

AC Dodd

Paul Inch

Brett Simms

Keith Calver

 

all have good reputations

[ollydc5]

Excellent advice cant wait to get my teeth stuck in