12 replies to this topic

[Black.Ghost]

I can soon start rebuiding my mini, but there are many decisions to make and I didn't think it would be this hard!

The first one is value for money, is a Stage 1 or 3 better on an SPi Cooper? The engine had previously been RR'ed at 65hp. Now I know this can vary and I know not 100% accurate etc but thats a pretty good start point. I believe a good stage one on a freshly rebuilt engine (so fully serviced as well) should get around 15% increase, so around 9 hp, putting me around 73-74 I would hope. A Stage 3 would put me around 85-90 I believe.

I want the car to be easily useable as an everyday car, but I love the idea of getting around 9 seconds 0-60 (based on a Cooper GP which had 85hp and 8.9 I believe 0-60). Reliability is important, but before I let the car stand for ages it was perfectly reliable and I had no real problems with it. I can get a Stage 3 Vmax Scart head for 350 that needs a clean and polish (not really a drama).

Will an Mpi Vmax Scart head fit and SPi engine ok? I dont want to get caught out on that.

Thoughts?

[Cooperman]

The expressions 'Stage 1' and 'Stage 3' don't really mean a lot as different suppliers have different specifications.

To get what you want youmight consider the following, without applying any 'Stage xxx' number to it:

A properly gas-flowed head with 35.6 mm inlet valves and 30.5 mm exhausts. Set compression ratio at c. 10.3:1
A Kent 266 cam
HIF44 carb on good smooth alloy inlet manifold
Slightly lightened flywheel
Better ignition system
LCB exhaust manifold
Maniflow twin-box 1.75" bore exhaust system
Better air filter (K & N or similar)
3.44:1 FDR to achieve the acceleration wanted

Build engine really carefully and accurately and time cam to 104 degrees ATDC with new timing chain to allow for 2 degrees initial chain stretch.

MPI head is not ideal because it has a different mounting for the alternator. Rob Walker Engineering will do you a really good head for a senmsible price.

[Fast Ivan]

I was under the impression that the SPI alternator doesn't mount to the head like the MPI, so when using an MPI head on an SPI you just dont use the holes in the MPI head, just leave them and bolt your alternator as you would normally on an SPI.
I thought the only difference between them was the added holes for the alternator on the MPI that you just dont use when bolting to an SPI, please correct me if I'm wrong though.

Edited by Rob Mac, 29 March 2013 - 10:34 PM.

[Kam]

If you want a bolt up kit and are taking it for a tune afterwards then I would go for a "stage 3" kit out of the two

I did and its the best thing I did to mine as mine was bog standard, I changed up a carb aswell at the same time (I know you're injection) and the difference was like night and day

Just make sure your mini is good to start with, no point in trying to put this stuff on a dying dog, and make sure your insurance is ok with it aswell for your premium etc

If you want to go into the engine that's upto you but as a "bolt on" basic kit these work, providing its tuned after - obviously

[Cooperman]

I got 85 bhp for an Endurance Rally Cooper (1990 1275 bored to 1330 cc) and all I did was to 'blueprint' the entire engine,
The head was very slightly cleaned up with the valve guide bosses being slightly ground away and combustion chambers slightly improve. The head had 35.6/30.5 valves, cam was MG Metro, ignition was Aldon 'Red', flywheel was slightly lightened, everything was matched, and cleaned up. Cam timing was set very accurately and exhaust manifold was standard 1275 Cooper with an RC40 twin-box system, all welded with skid plates for rallying. A centre main bearing strap was fitted and the head was skimmed to give 10.5:1 C.R.
It gave 85 bhp at the flywheel at 5800 rpm and the final drive ratio of 3.44:1 with standard gear ratios gave 0 - 60 in about 9.2 seconds (as accurately as I could measure it). With the rally suspension and general driveability it was, and I believe still is, a great little road car.

[iMurray]

having the same thoughts myself :) i know minispeed's kit claim 85bhp, and i suppose if you didnt get that you could argue that they should tune it until it reaches that i dont have the money to do this at the moment but im in the same boat! i was swaying more to a stage 3 kit... but remember you can buy all the parts seperately... so you could buy the cheaper stage one for now... then pick up a head, the rockers, etc which makes it up to a stage three in time... i wouldnt put a harsher cam in if you're going for a road engine myself... my plan is to leave that out as i want a nice smooth performing mini... but there could be a cam out there which provides the ebst of both worlds. bye bye mpg!

[Kam]

That's a dam good setup but out of reach for most, when people see a "kit" to effectively bolt up they will just head in that direction. I know that's a cop out but that's what I did as your setup was not easy for me to get or from others that had proven setups aswell but looking at a kit was, went from factory 54ish to 70bhp with a stage 3, car was surprisingly more fun to drive on roads or motorways, did another 10k in that in one year, its still the most reliable engine I've ever had

[Noah]

1.5 Ratio Roller Rockers and a Ported head, will emulate the higher lift of a kent 266 cam. This is what I'm doing, the also reduce wear, and they look the dogs danglies.

If you speak to ACDodd, a sprite engine (like mine) with the same spec achieved 80 odd BHP at the fly-wheel, on the same sort of mileage.

I won't be going any further than that, purely because of insurance costs. But 80 at fly, whats that, near enough 70bhp at the wheels?

I'm pretty happy with that spec' at 17. Should munch Corsa's for breakfast lunch and dinner, but still be a drive-able car.

I personally would stay away from the kits, you can build much better ones by buying the parts separately, therefor choosing the exact part for your engine not the pre-determined one!

Edited by Noah, 29 March 2013 - 11:56 PM.

[iMurray]

this what i be doing instead of cam :) have fun with that insurancee noah

[Noah]

this what i be doing instead of cam :) have fun with that insurancee noah

Still cheaper than a 1.2 Clio... Live in London, on a Main road. 5k for the insurance.

Insurance quote for the Mini (I've been getting quotes to make sure) range from £1600 - £2200

2200 is what my sister pays after 2 years of driving on a Clio. So, I'm happy.

[Kam]

The bolt on kits are just an easy way out, not the best long term but how many people actually go into the exacts of what they need for there use compared with just buying something and chucking it on, the easy way out always usually wins

[Black.Ghost]

Guilty of taking the easy way out. But having said all of that, I don't understand engines enough at the moment to do it all myself.

I know I want the end goal, ideally, to be around 85-90 hp. And I want it to drive nicely on the road.

I was told that getting something like the SW5[b]i[/i] cam would help get the most out of the modified head etc.

The engine is being rebuilt anyway so it will be in decent condition and its not just a case of bolt on some new bits.

And I now vaguely recall that being the only difference about the two heads.

And I will definitely being staying with injection. I never had a problem with it before and so dont want to mess with that side of things.

Edited by Black.Ghost, 30 March 2013 - 12:19 PM.

[Cooperman]

One thing to make sure of is that the compression ratio is correct. The only sure way of doing this is by measurement and calculation. It is no good relying on the suppliers to get it right even if you do give them all the dimensions.
So the two important measurements, which you will establish when doing the 'trial build' before final assembly, is how far down the bores the piston tops are from the block deck. Ideally after the trial build the distance of the piston tops down the bores at TDC should be a maximum of 0.005". This is achieved by skimming the block deck after trial build. Once that is known the ideal combustion chamber volume in the head can be calkculated and the head face skimmed to give that volume.
I once had a head from a well-known vendor (not Mini Spares, the other one!) which was for a 1071 Cooper 'S'. I specified the desired volume, but on checking it was not correct and was a few cc too big. In other words it was just a flowed head for a 1275 engine, not a 1071. Trust no-one, measure it yourself.