15 replies to this topic

[dedge]

Hello,

I am new to this forum, and to the mini scene too. I own a 1993 British Open since a few years which I use as a week-end toy. No track warrior here, but I raced on karting and racecar for several years so I have a bit of handling on this little machine, and know a bit too on how to set it (chassis-wise)

The car today has mainly be modified for reliability reasons and to have a bit more fun while driving : adjustable arms or brackets to have a modified geometry (reduce the understeer etc), EBC green brake pads, new rear drums, HiLo kit for a lower stance... So far so good, on tight roads it is a real pleasure to drive fast and some young drivers might still be surprised so see me on rear view mirrors of the small hatchback despite a real lack of power!

 

And this is why I am writing : I would love to have a bit more power to add a bit more fun, particularly on mountain roads (I live in France, near the Pyrenees...)

 

Here is the actual spec engine-wise :

- Engine is still a 1275cc. Car has been bought second hand and I am quite sure the engine has been changed : the block numbers are saying it was a SPI (12A2DJ92XXXXX and I had a sensor on the flywheel case) but the car was a carb version (the last ones) as per the car serial number (SAXXNYADRBD). Must be a Low Compression

- MiniSpares aluminium cast inlet (not modified) has been put

- HIF38 carb (the one supplied with the car) with AAM needle

- Fletcher LCB manifold (42mm OD, might be 1,5"ID?) and down pipe (44mm OD), RC40 rear box

- 2,76 diff ratio

- K&N filter on genuine air box

- Lucas 65D (with SPI curves?)

- 12G940 head (not modified)

 

The car is running fine, no real reliability issues during the last 5000km, it starts well, run well, no major leaks, no strange noise or fumes. It can go up to 130-140km/h on flat, but no much by itself, I do not know if it is normal, I find those numbers a bit low. I do not have a tacho to give the rpm (only 2 dials on the dash)

The gearbox is OK, the 1-2 is a bit rough when cold but makes no noise, only the first gear is making some noise if the car has been left idling for some times (better if you put the 2nd gear, than the 1st, so gearbox will have to be rebuild, it is not an issue).

My goal is to have a car with more power to overtake easily and climb the hills in 4 (the low diff ratio does not help), but still be driveable on highways without too much noise (speaking of 110km/h roads). I do not want a race engine, or a car with very close ratio gears.

 

I was thinking of making a complete overall of the engine with +20 high compression pistons, a bit of machining to higher the compression ratio if needed (will have to be measured I suppose), a ported head, HIF44 carb with my alloy inlet machined (it has a small lip inside actually), MiniSpares Evo cam, a 3.1 diff, maybe a lightened flywheel. Of course the gearbox and clutch will be rebuild and the gaskets changed everywhere. Those are the changes I rear here and there.

I have some doubt whether or not the exhaust system will have to be changed, and if the 65D distributor from the SPI will be fine.

 

So here my questions :

- are those modifications suitable for what I want to obtain?

- what are the figures (horsepower) I would achieve if everything is well made?

- will it really change the handling of the car or is it too much money to spend (approx £2200) for just a small change?

 

thanks for your help!!!

[DeadSquare]

If you will be going up mountain roads, the very best thing that you can do to get more power, is to fit a supercharger,which will be especially suitable if you have a low compression engine.

[dedge]

The thing is : I am french, so as the car. The modifications are not allowed on cars hère, and any obvious change from the original vehicule configuration will prevent you from obtaining the french equivalent of the MOT.
Plus, no need to tell you what could happen in case of accident, the insurance expert will easily detect the change and void your contract.
So adding a turbo, a supercharger... is not possible

[cal844]

What is say is change the diff, if it's a 2.76:1 ratio it's really low geared so you can fit either a 2.9 or a 3.1 diff(I'd recommend the 3.1 or a 3.44).

Don't be scared to rev the engine if down changing to third, or second. I usually try keep the engine under 5500rpm if down changing.

You should also consider when the car was last serviced, 3000 miles and use a good quality 20w50 mineral engine oil with high ZDDP levels. I use Comma Classic in my minis, but I'd recommend the valvoline VR1 as it will give better protection for longer

[dedge]

I use Gulf Classic 20w50 oil, with 2400zppm, filter has been changed right after buying it, then 3000miles later.
No issue with downshifting but most of the time it only changes the amount of noise, not the speed!

[DeadSquare]

The thing is : I am french, so as the car. The modifications are not allowed on cars hère, and any obvious change from the original vehicule configuration will prevent you from obtaining the french equivalent of the MOT.
Plus, no need to tell you what could happen in case of accident, the insurance expert will easily detect the change and void your contract.
So adding a turbo, a supercharger... is not possible

and any obvious change from the original vehicule configuration will prevent you from obtaining the french equivalent of the MOT.

 

But surely, don't all the french people disregard all the regulations ?  That is why we want to leave the EU.

[unburntfuelinthemorning]

If you have access to a rolling road dynamometer it would be worth going and checking how well the engine is set up.

 

Tuning the engine further would of course increase the output.

 

I think the main issue though is the rather high final drive ratio as cal844 has mentioned.  That very high fourth gear is great for long distance cruising and lowering cabin noise levels but not for acceleration or top speed.  

 

If you're rebuilding the gearbox then put a lower ratio in while you have the gearbox in pieces.  It won't cost a huge amount but will make the car so much more lively.  You'll zip through the gears and will have a higher top speed too. 

 

140 km/h isn't that great; my 998cc Mini can just about do that - mine has a 3.76:1 FD ratio, it wouldn't get near that with a 2.76:1.  In yours I would go for a 3.44:1 as you say it's a weekend toy.  This is what the old 1275 Cooper S had as standard and it works well.  Everyone will have a different opinion on the correct ratio to use and you'll need to make your own decision on that.

 

This link may help too:  http://www.retromini...d=19&chapter=20

[DeadSquare]

OK, to answer you questions, sensibly.

 

Polishing and matching the manifold will help.

 

For road use, a 38 SU is as good as a 44 as it keeps the gas speed up.

 

Your exhaust is fine and the rear box is dependent on french noise levels.

 

I'd stick with that diff for the lower noise on autoroutes and accept that you are driving a 60 year old model when you change down on the hills.

 

If you are not on dusty roads, you could remove the filters, but it won't make much difference.

 

The distributor will depend on your eventual engine modifications.

 

Money spent on a well modified head is never wasted;  go for the best that you can find/afford.

 

 

 

Rebuilding the gearbox.  It will improve the joy of driving when it has done 10K km

 

Overtaking should be safer, as the modified valve springs will allow higher RPM.

 

 

 

Assuming that french fuel is the same octane as in England, aim for about 9.5:1 compression ratio.

 

Head and carb, have been mentioned;  by all accounts, the Evo 001 cam seems a good choice for road use.

 

A lightened flywheel can easily be done later, if trying to keep within your budget.

 

 

 

 

Your suggested modifications will help, but you probably need a 2500cc engine to satisfy what "you want to obtain"

 

Who knows how many horsepower you will get.  More important, is how much more torque you will get.

 

From your description, the existing suspension modifications will cope with your expected increase in power.

 

 

 

 

Bon chance.

[nicklouse]

Oh the French test worse than the TUV.

I would look ad a FD change I would also consider a worked on head and then have the inlet worked on and fit an HIF44 with standard housing but with a KN element in it.

What RPM are you reaching?

[dedge]

As I said, I do not have any clue about my RPM as I do not have any tacho (2 dials only), and I have sold my Alfano/Mychron I used on tracks...

It might be a week-end toy, but I do not expect a race/track car. It might be from the 90s, I accept that it cannot be driven like any car from this area. It is a "classic", I am ok with that, I just expect it to be safer when overtaking , and climb the hills better (today, on highway it is sometimes a bit dangerous to be pushed by trucks at the first climb). It makes approx 50hm from the factory, maybe 53-55hp with the stage 1, so if I can be close to 75hp it might be very good. Yes I talk about hp, but it is the torque that I search, you are right DeadSquare.

 

I understand that the diff ratio is my main issue. It is not surprising for me. But in order to change that, engine will have to be put out, gearbox too, so I suppose that it would be the right time to also change the cam, the clutch, the pistons, valves seals...

The car itself is approaching 100.000miles, engine has been changed but I have no recording. When the head gasket has been changed 3000miles ago (because of a small water leak on the front, caused by rust pushing between the block and the head), no issue has been found with the cylinders, so I suppose it can be kept and tuned

The head seams also another big topic. I will see what the cost will be, I do not live far from "WG Racing" who is having a bit of success in Mini races, even on your island. But I fear the price will be on par with their racing pedigree, and I do not want a race engine. Valve spring might also be needed as I have already felt the valves "dancing" at high rev, even after a rocker adjustment.

 

Well, if I understand well, from priority POV :

1 - gearbox (central pick up) /diff ratio

2 - cylinder head, inlet maniflow machining, HIF44, and machining to have 9.5/9.6:1 CR (our fuel is 98 octane)

3 - EVO 001 cam shaft

4 - lightened flywheel

5 - maybe ignition distributor?

 

Steps 1 to 3 need the engine to be put out, I guess I will need to secure this budget before an attempt!

Thank you for the confirmation of what has to be done, I will do my maths and hope to launch the modification asap!

[nicklouse]

the diff ratio change does not actually need the engine off the gearbox but if it is out you may as well do the rest.

 

re the head one of the modded ones from Minispares (done by Keith Calver) should not be over looked.

 

4 if you do dont forget it will need balancing.

 

5 get the current one recurved if needed.

[Rorf]

I would definitely go for the 2500, save your francs

[Spider]

If the engine and gearbox are otherwise fine (and it sounds like it from your general description) then other than a clutch change, fix any oil leaks, there's no need to do anything else while the engine is out.

 

All that's needed to change the final drive ratio while it's out is to remove the radiator, the Speedo Drive Housing and the Diff Cap to change the final drive ratio. I would actually suggest building up a reconditioned diff before doing the swap as the diff will almost certainly need an overhaul.

 

But surely, don't all the french people disregard all the regulations ? 

kinda reminds me of a little incident that occurred in 1966,,,,,

[Cooperman]

I built an engine for an 1990 Mini Cooper 'Endurance' Rally Mini a few years ago. The regulations specified a 'completely standard' engine and gearbox.

I carefully built it to the following specification:

 

MG Metro cam

Lightly re-worked cylinder head with 35.6 mm inlet & 29.5 mm exhaust valves. Original Cooper 'S' forged rocker shaft.

Compression ratio 10:1

HIF44 carb on cleaned up inlet manifold

ITG air filter

RC40 twin-box exhaust with centre exit end pipe.

Discretely lightened MK.1 flywheel and Mk.1 Cooper 'S' clutch assembly

3.44:1 Final Drive Ratio

Aldon custom distributor.

Bored to 1330 cc (that's +0.060") with 21253-60 pistons

Dynamically balanced

Centre oil pick-up

Cross-pin diff.

Cam timed to 2 degrees advanced from nominal

Duplex timing chain/sprockets

 

It gave just over 80 bhp at the flywheel and went very well. In fact, I have  just bought it back after selling it in 2005.

[dedge]

Cooperman : so what to expect from the changes I am about to do? As there will be many differences with the configuration you expose