49 replies to this topic

[welshdan]

Also it depends what driving you do. If you do some duel carridge way blasts etc, it might be worth considering a 3.4 or 3.6, at least thats what id go for. A series engines like to rev, especially with the cam you propose. You dont want to kill this by over gearing it, but if its for road a reasonable rpm at cruising would be nice!

[crock]

I think the comments made above forgot to include your 7 port head and twin Webers. The low end drivability will be considerably better than a 5 port. You should be able to get that to work from 2000 rpm in top gear without stumbling though it won't pull hard. I don't notice a lot of difference at 70 mph between a 3.44 and a 3.1, however I sure wouldn't want a 3.9 or 2.7.

[Pigeonto]

For what it's worth, I'd go for a 3.2. But I stress I havent tried one: I built a 1380 with just over the magic 100hp and wished that's what I'd used. With the potential output of your engine it should be a good compromise,which is all that any ratio will ever be.It's not been mentioned so would be worth some discussion from people with experience of that. Once you are into straight cuts,different drops,different gear sets it must be a whole new world! beyond anything I've done.

[KernowCooper]

I think the comments made above forgot to include your 7 port head and twin Webers. The low end drivability will be considerably better than a 5 port. You should be able to get that to work from 2000 rpm in top gear without stumbling though it won't pull hard. I don't notice a lot of difference at 70 mph between a 3.44 and a 3.1, however I sure wouldn't want a 3.9 or 2.7.

I'm not sure you want to be down that low with a 286 and 1.5 rockers, the duration of the cam and that kind of overlap even with better breathing of the 7port head.

[Cooperman]

^{With a SC CR gearbox, 1st gear is very high, so a low final drive is necessary to pull away in traffic or up hills and the result is more 'frantic' revs at cruising. The 286 is not really a cam for daily driving with any amount of traffic and the need to use over 6400 rpm to fully use it means more regular re-builds and a lot of clutch wear due to having to 'slip' it a lot to pull away. The 1.5:1 rockers will lose you a bit more at the bottom end whilst adding only about 2 bhp at over 5500 rpm. I don't want to seem to be criticising your specification, but that spec is really suited more to a full-on rally car which would have a very low FDR like 3.9:1 or even 4.1:1. Once you start on really 'top-end-power' cams, like the 286 you are in the realms of very specific use and you then can't have an 'engine for all applications'. There is no point in having a cam which loses you most bottom end - the range you need in traffic - but which puts the available real performance in a rev range where you are reluctant to drive. The other issue is that using those revs as needed will mean higher bore wear and at 1380 when a re-bore is needed you may well have to source a new block. If you don't use those sort of revs all the time, i.e. 5500 to 6700, you will actually have less actual available performance than if you used a 266 or similar cam. To summarise, to keep a 286 cam performing as it should within the optimum rev range of 5500 to 6700 you need a straight cut close ratio gearbox. That gearbox with its high 1st gear requires a low final drive ratio and that restricts the cruising speed, but a car with a 286 is not intended for main road cruising, it's intended for rallying where the car is flat out at high revs most of the time.}

[welshdan]

As cooper man said close ratios are a must. I prefer them even when using a mild cam but they come into their own with higher lift cams. Also true that it will need more rebuilds with a racier cam, general wearand tear, also clutch, higher revs needed to make it work etc. How you time it in will effect how it drives. Also what ignition do you plan to use? My brother ran a 1380 with a 286 as a daily for years, it did.need regular rebuilds, he has since gone on to a 296 in his new engine. Its a road car but not used daily now. These cams can be used to good effect on the road, its due to what you percieve as acceptable, it certainly wont be anything like a modern car to drive.

[KernowCooper]

You'll get a few looks in the high street pulling away on a slope for sure.

[welshdan]

Just to add i use a 3.2 fd on my mpi cooper, 13s, close ratio gearset, its fine to pull away etc, but i use the sw5 which will help.as it comes into the power band much quicker than the 286. I also use a sccr set in my turbo, 13s, 2.9 final drive. This is a different ball game all togher with an fi engine. It is a bit slow to get off the line

[Cooperman]

No matter what you do to a Mini, it is not going to drive or perform on the roads like a modern car. I know that when I had a standard engined Endurance Rally Rover 214, it was so much quicker over a given piece of road then my Cooper 'S' which is a real 'full-on' rally car. Even a 1.4 Fiesta will cruise better than a Mini. But, with a Mini you are driving a true 50+ year old classic design of car and that is what it's about and where the fun it. If you want to make it go better than other Minis that's great, but before choosing an engine specification the use to which the car is to be put needs to be defined. Then, when you know that, and if a lot of cruising is to be done decide what sort of revs you want to be pulling at those speeds. From that a look at the cam charts provided by the specialist cam grinders can be consulted and the obvious cam will show up. For example, for a road car you might decide that on motorways you would like to be pulling around 3800 rpm at 70 mph. This will define the FDR and will enable you to choose a cam which has best torque at just below that and best power at not to much above that. Then you can see what speeds and revs you'll be pulling in the gears to optimise the torque and power as you drive along.

[critchie2006]

I've contacted the company to ask if I could swap my cam kit and that's not a problem. So a 266 or a 276? Also looking into the SCCR gearbox. Better sorting this out while the engine is out and stripped

[wile e coyote]

Just my 2p worth but given the rest of you outline spec and desired use '266 would be a bit tame so of the two options - 276 has it.... oh and 3.44 or 3.65 diff....

[KernowCooper]

My Kent 276 pulls well from 2000rpm and has good road manner as its listed as Fast Road/Rally Cam by Kent, and has a bit of a lumpy idle but nothing untoward and doesn't need 3000rpm to pull away, and would work well with a 3.44diff to produce a quick Mini with acceptable 70mph revs

[mike.]

I'd say a 276 with 3.44 final drive.

I have a morspeed phase 3 cam which is very similar to a 276.

It idles at just over 1000rpm with an ultralight flywheel, power is strong from 2000-7000rpm and still had good torque for road use.

Edited by mike., 20 March 2013 - 02:45 PM.

[welshdan]

This is probably the ' sensible' option, but you cant help thinking that you should have gone for the 286 a few weeks after you get it on the road and get used to the 276...

[critchie2006]

This is probably the ' sensible' option, but you cant help thinking that you should have gone for the 286 a few weeks after you get it on the road and get used to the 276...

That's what I'm worried about :) I've never been known to go down the sensible route. Think 276 and 3.44 is popping up a lot and could be the best option.