16 replies to this topic

[mini-geek]

I'm building a "period" tuned 850 I'm just not sure on spec..

First off will be a 12G 206 or 295 (998 cooper head) unless anything else can be suggested

Twin HS2's

Now the block is where I don't know what to do, and I'm open to opinions or options, I know it needs a rebore and not sure what's the most it can be bored out to?

Cam.. no idea..

Lightened flywheel and possibly some work on crank and rods if funds allow..

Any examples of spec for similar builds?

[Cooperman]

The problem with the 850 engine is that the crank is relatively weak and the pistons are fitted to the rods with pinch bolts.

 

Pistons can be a bit hard to find and if a 295 head is to be fitted flat top pistons are vital, as is decking the block to bring the piston tops absolutely level with the block deck in order to get the required compression ratio. In fact it can be difficult to get the C.R. high enough.

 

Quite honestly it is not possible to get reliable increased power from an 850 such that it will be as quick as, say, a 998 Cooper. In fact a reliable 45 to 48 bhp is about the sensible limit. Now before someone comes along claiming 65 bhp+ from an 850; yes, I know this is possible, but on a full-on race engine with a relatively short lifespan.

 

Make sure you sort the pistons before going any further. It is not worth going beyond about +0.040", but you will be governed by what is available.

 

Not much can be done to the crank to allow higher revs unless you get one specially machined from a billet of steel (maybe £1200+) and use special rods.

 

An alternative is to build a 998 engine which can go to around 1060 cc and which is much stronger and easier to modify.

[mini-geek]

Thanks, great info there! And highlighting some ot the things I was concerned about..

So another thing I had been thinking of doing is building a 998 cooper engine, a genuine one will be silly money now but if I get a pre a plus block I can make it look right

[carbon]

Starting with a 998 unit for tuning makes a lot of sense, unless you're really set on a tuned 850.

 

And once installed will be difficult to tell difference between 850 and pre-A+ 998 from appearance alone.

 

But will be very noticeably different when driving...

[mini-geek]

Not really set on an 850 at all really, as it's a period car it's probably more in keeping to have a 998 than an 850

[hazpalmer14]

I've got a slarke modded 12g202 if it's any use

[Spider]

Have a chat to OMP here on the forum, he's an 850 guru.

 

There's a range of pistons still available for these engines.

[Cooperman]

Personally I can never see the point in modifying an 850. An 850 is ideal to produce an 'as original' car with maximum value or to experience just how slow the original Mini actually was. My October 1964 car is to be original except for dry suspension which seems acceptable to everyone now.

 

A pre A+ 998 engine is identical to all post-1964 Cooper engines and with a 295 head and the correct cam, carbs and manifolds it is a Cooper engine in every respect. Visually it is the same as an 850, but with the 98 up to around 65 bhp is easily and reliably obtained.

 

It depends on how much originality is wanted.

[carbon]

Typical spec for a 'period style' fast road 998 would include:

- MG Metro or MD266 type cam. 8mm (std) valve lift for 'quick', 0r 9.5mm for 'fast' driving style

- 12G295 or well modified 202 cylinder head. CR about 9.5 to 10:1

- Twin HS2s. A modified HS4 on good alloy manifold (Oselli or Howley) also works well.

- Maniflow freeflow or small bore LCB with twin box RC40

- between 3.44 and 3.76 diff, depends on use / driving style

- 4 syncro 1128 box with 'S' input and 1040 laygear

- std flywheel fitted with ultralight steel backplate & rebalanced

[Cooperman]

'Carbon's' spec is excellent.

But remember, if you do such an engine it will give c.60 bhp and the drum brakes on an 850 will be far from ideal.

[mini-geek]

Yep cheers that's the sort of spec I will aim for, just need to sorce the parts, and decide if to stay magic wand or go remote

Yes I think a set of cooper s brakes with servo (servo is my personal preference) will be in order.. just need to stumble across a set of S wheels

[Cooperman]

If you want to keep it looking as-original you could fit a set of 998 disc brakes with Mintex 1144 pads and a servo. Then the original 3.5" wheels will fit and it is a real 'period modification', as it a 998 engine with twin HS2 carbs. Some people knock the 7" discs, but back in the '60's we rallied on those brakes and they were fantastic compared to the single-leading-shoe brakes of the 850.

'S' wheels don't look right on a Mk.1 850.

[AlexMozza]

I think there is something very satisfying about a well built, standard 850 engine.
Having built one for a woody last year, was one of the smoothest engines I have ever driven.
I think people are to interested in what power is produced, I think a lovely 850, well built and balanced will put a pretty big smile on your face!

[OzOAP]

There is a huge 850 market, as early cars are becoming more valuable.
I have a waiting list of 850 customers, (thats customers that want 850 engines, not 850 people wanting engines...unfortunately),but until the piston situation is sorted they will have to continue to wait.
I have looked into getting pistons made, up to 50 sets, but it is not financially viable yet.

[mini-geek]

Oh? Wasn't aware of this? What's not available? Standard or oversized?