25 replies to this topic

[Cooperman]

Best to just make it bigger!

Ac

Oh no, that takes away the real iconic and classic driving of the original Mini as conceived by Sir Alec Issogonis 60 years ago.

It is not all about modern-type performance, it is about preserving the type of classic motoring we enthusiasts had back in the 1960's when we were impoverished young people doing our own modifications on the cars we used every day on the roads. 

 

My friend got an 850 for his 21st birthday in 1961. We did some work on the head ourselves using a spare head we bought very cheaply, had it skimmed at work (de Havilland Aircraft Co.), cleaned up the manifold, inlet & outlet sides, and changed the air filter. It was a great little car and we used it to win an area rally championship. It had single-leading-shoe front brakes, 3.5" wide wheels with Michelin X tyres and we ran the lines inside the car. An early-type sump guard and 3 spot lights completed the car with some additional instruments.

 

At that time this mildly improved 850 was great and to re-create that sort of performance now is truly classic car owning and driving.

[surfblue]

 

Best to just make it bigger!

Ac

Oh no, that takes away the real iconic and classic driving of the original Mini as conceived by Sir Alec Issogonis 60 years ago.

It is not all about modern-type performance, it is about preserving the type of classic motoring we enthusiasts had back in the 1960's when we were impoverished young people doing our own modifications on the cars we used every day on the roads. 

 

My friend got an 850 for his 21st birthday in 1961. We did some work on the head ourselves using a spare head we bought very cheaply, had it skimmed at work (de Havilland Aircraft Co.), cleaned up the manifold, inlet & outlet sides, and changed the air filter. It was a great little car and we used it to win an area rally championship. It had single-leading-shoe front brakes, 3.5" wide wheels with Michelin X tyres and we ran the lines inside the car. An early-type sump guard and 3 spot lights completed the car with some additional instruments.

 

At that time this mildly improved 850 was great and to re-create that sort of performance now is truly classic car owning and driving.

 

Totally agree with your approach Cooperman, I dont want my Mk1 to be anything but an 850, (unless over sized pistons required)

[Spider]

As Cooperman touch in in his post (at post #14), some of the issues with the 850 isn't just that it's an 850, but the components within are only designed for the low power outputs of these engines.

 

By the time you not only tuning it to get more from it and spend loads of cash along the way to make it hang together longer, you will have spent some considerable cash - well exceeding what you'd spend on a 998 or 1275 - including their initial purchase.

 

This is not to talk you out of it, as I do see an appeal there, but just be aware that this won't come cheap for modest overall results.

[Cooperman]

I got my first 850 Mini in 1963 when I was 22 years old. I loved that car and did around 23000 in the 14 months I owned it. I did a bit of improvement to the engine and it went quite well. Then in 1964 I bought a new 998 Cooper which seemed much quicker with its 55 bhp!

The old 850 had its own charm and is a great classic car now. There is no need to make it seriously quick, even if that were possible. Just drive and enjoy as it will show you what driving was like in the '60's when driving on country roads and lanes.

[Chesterman]

The problem with the 850 is the rods have pinch-bolt small end location and the normal pistons are not very strong.

The crank is also a limitation and even fully balanced it is not wise to rev it much over 6500 rpm. Of course, one could get a billet crank machined for a cost (high).

There used to be a competition crank available back in the early 1960's, but I doubt one could be found now.

However, the 850 does respond well to improvement so long as mega-power/revs are not wanted. With a modified 12G295 head, a better cam and a small-bore LCB or Cooper 3-into-1 exhaust manifold, plus either a pair of HS2 carbs or a single HS4 it is easy to get c.45 to 50 bhp.  Don't set the CR too high as those split-skirt pistons will not like anything much over about 9.5:1. A 266 cam should be very good, or maybe a Mini Spares Evo001.

Be a very nice retro build and really nice to drive.

 

Don't mean to bump an old thread but just wondering whats the largest cam you would go for on an 850 for it still to be reasonable on the road? Would 266 be the largest thats usable?

[Cooperman]

I certainly wouldn't want to go beyond a 266. The Mini Spares EVO001 would probably be about ideal.
Whatever you do to an 850 road car it is never going to be quick. It will, however, show you what driving was like in the 1960's.

[Minigman]

The MG1100 cam works well in a 850.

Edited by Minigman, 23 May 2018 - 08:02 PM.

[minitravellerman]

Back in the late 60s, my dad tuned his 850 to the Special Tuning Book.

Spec if I can remember it correctly was;

 

Standard bore 

12G295 head with 80thou skimmed, polished and ported

997 Cooper cam

MG1100 manifold

Speedwell 1.5:1 high lift rockers

twin 1.25" carbs with Speedwell ram pipes

twin blade fan

Special Tuning competition centre exit exhaust

 

I'm sure there's something I've forgotten but he said it was a real wee screamer and could take standard Ss off the line. Always fancied building a replica of his old car. 

[ACDodd]

Tuned 85O for the road, hmmmmm 53lbft of torque. Less is most definitely not more in this case!

Ac

[mab01uk]

These earlier thread may be of interest.....

 

Tuning The 850 Engine, Formula 850:-

http://www.theminifo...ne-formula-850/

 

Tuned 850 Engine

http://www.theminifo...ned-850-engine/

 

 

 

Also for interest, the most powerful high revving 850cc A-Series Mini engines were probably those built with special Longman short stroke steel cranks for the Special Saloon Racing Mini's in the 850 'Free-Formula' class back in the 1970's. The 850cc class was full of destroked/overbored 970 Cooper S engines usually running exotic 8-port heads and the like.

Quote- "the stroke's so short the pistons only quiver in the block!!"

 

This 2 cylinder 850 BDA was designed and built by Gordon Allen from half a 1700cc BDA (so rated at 850cc). It was a real winner once a few niggles were overcome. It was used by Peter Day in a Mini and also a Fiat 500 (the "Mighty Mouse") Here it is at home in the Mini;







 

Edited by mab01uk, 23 May 2018 - 10:55 PM.

[OzOAP]

Latest edition of Mini Magazine has a feature on one of my tuned 850s.
I'm currently doing 2 others.
Let me know if I can help

www.facebook.com/ozoap

Edited by OzOAP, 24 May 2018 - 09:46 AM.