A-series tuning

When you are buying a new cam for an A series, then you should get a new oil pump as its got to come out to fit it and then you can buy them as a pair (and it makes no difference if you want the peg or slot drive, see which they have in stock).

Cam choice, for a fast road mini (espec if your not doing the head) I would be looking at a Swift tune SW5 or a Kent 256.

Manifold wise, I would go for a freeflow cooper, fits and seals so much better, you get slightly more torque and I even used mine on a 90bhp 1275.

The other thing to look at is the head. The 850 head is very restrictive, if you can't afford a 998 cooper head, then try and find the head from a 1100. It will need skimming (like the cooper head), but it is better than a stock 998 head

hope that helps a bit

To start tuning an A series, the first thing I'd suggest is to increase the capacity. By hanging on to an 850 you're really restricting your options. 998s are ten a penny, will give far better results, and your insurance company really shouldn't mind.
On any tuned "small bore", the Cooper freeflow is far better suited to the application than an LCB, as you're simply not moving enough gas to trouble it's ability. Also, it's easier to seal and quieter than an LCB. Don't buy cheap exhaust manifolds - there are some VERY poor ones out there, and Maniflow really aren't that expensive. Also, have a look down the pipe of the backbox you want so you can see inside the "can". If it's a perforated straight through tube, then rock on. If it's a perforate tube crimped at one end and another of the same leading to the tailpipe, don't spend any money on tuning the engine, it's a waste of time as the exhaust will be plugging the system up.
The 998 Cooper head (12G206/295) is a very good head, but has huge chambers and needs a hefty skim (~0.080") to get the compression up. The standard head thickness is 2.75" iirc, so measure any you look at so you know whether to skim it or not. Beware of over-skimmed heads - it's common for people to take too much off 295s and break into the waterways. Another option is to use a common, cheap and even better 1275 head (12g940) and either recess the exhaust valves 0.040", or have the block deck pocketed to clear the valves. The latter is the only real option if you use a high-lift camshaft.
Lastly, camshaft choice is pivotal, as it dictates the necessary compression ratio, amongst other things. Bear in mind that the SW5 whilst extremely good, is also very tame, and best suited to lazy, tractable big-bore engines. Everything's over by about 5500rpm, and a by their smooth nature, tuned small-bores love to rev (though not 1098s - revs kill 'em!).
As is always the way - your car, your choice, but make Vizard's yellow bible your first upgrade, speak to people running tuned small-bores for advice, and make educated purchases rather than buying cheap or because "bigger is better".

Hmm, the problem is that the budget for the whole car is just over a grand, so £400-500 on the engine really isnt gonna happen unfortunately. The only money for this project is coming from selling my motocross bike (no luck so far )

Bearing in mind my budget, would i be better off with a stage 1 kit and just giving the engine a decent rebuild and service?

Oh, tarmacadam - The brakes are definately gonna be looked at, perhaps some cooper discs uo front. All depends on what moneys left after the rest of the build ;/

The yellow bible (Vizard) is essential.

While the cam is matched with the oil pump, you must not forget that a 850 hasn't got any cam bearings. So you cannot install a 731 cam, because it cause too much wear. You could offcourse fit bearings in it, but otherwise you pretty much stuck to the 510 profile or the SW5., let's say up to 250 degrees.

An interesting option is to keep the crank and put in a 998 block, you get a pretty square (bore/stoke) engine (976cc?) which will rev, provide you can pump enough mixture in it.

There is plenty of meat in the stock head is pretty poor, but simple modifcations to the combustion chamber and ports make it a lot better (not as good as a cooper or 12G940 head though).

cgi.ebay.co.uk/Mk1-Mini-Riley-Elf-998cc-Engine-/220709995722?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item33635744ca

hhhhmm

Eeuuh, cam is in the block. It's OHV not OHC.

But you could also put a BMW k100 head on it ;D

Stage 1 kit is a must for anything you do.
The standard intake and exhaust systems strangle the poor little A series.
A stage 1 kit can realease up to 20% more power once you've got the carb jetted and set up right

How would finding 998 pistons be difficult?

I said interesting, not cheap

Well, you will need higher pistons since the stroke is shorter and/or the block had to be skimmed to get the top of the piston level with the top of the block.

More info on 850 tuning:
www.turbominis.co.uk/forums/index.php?p=vt&tid=125219
www.theminiforum.co.uk/forums/index.php?showtopic=39291




I would look for an A+ 998 instead of the Riley engine that should go into a Elf again.

Good luck!