experiences of tuned 850

[anonymous-user]

Hi,
I am currently rebuilding an 1981 850.

I really do not want to to go for a larger bore engine burt would like just like little more out of the 850 it's self to help with hills etc..

I know there are millions of threads and books on what can be done with mini's but I am after owners personal experiences with tuned 850 engines and what mods they have done.

look forward to hearibng form some of you...

[Pixel-Snapper]

I kept my 850 very simple really.

1000cc head slightly worked on

1.5 SU carb

K&N air filter

Maniflow manifold and Exhaust

Used to be pretty quick had plenty of poke but not as much top end as the other boys in the club with there bored 1275's... but hey I was 17 and having fun all the same, eventually seized it after not checking the oil.... college boy error! Used to sound lovely though screaming round the rev counter.

Then put a stnadard 1000 in and that wasnt as much fun.

[uksurvivor]

I had a purple 850 mini pick up 18 years ago :'( lowered, negative camber with 10 x 5 revolutions 1.5su, LCB with a straight through pipe to a spitfire back box (very noisy!) and a cheap foamy air filter that used to cruise happily (ish) at 90 (on the speedo) for 40 odd miles every day twice a day.

No engine tuning just a well maintained ignition system and a well lubricated drivetrain. Probably the most free revving and fun car I've ever had and it taught me a great deal about maintaining momentum which helped me out in my later attempts at 100cc kart racing!

[Cooperman]

The biggest limitations to tuning the 850 are the crankshaft and the fact that the cam runs directly in the block with no cam bearings.
The standard head is absolutely dreadful and the comp ratio is low. Howevre, the pistons are split-skirt type, so won't take any abuse from a super-high C.R.
An 850 to the following spec might be good:

Gas-flow the head, install slightly larger inlet and perhaps exhaust valves (or fit a 12G295 Cooper head) and set the C.R. to around 9.6:1.
Fit a 3-into-1 tubular exhaust manifold
Fit an HS4 carb on an alloy inlet manifold, or maybe a pair of HS2's
Use a Kent 255 cam
Get a 998 Cooper exhaust system
Make sure the distributor is 'as new'.

Use around 6000 rpm as the crank limit.
You might want or need to get the block line-bored to take cam bearings.

The 850 really is a great little engine and represents the basic spirit of the Mini.

[anonymous-user]

Thanks for the info!

I have had many Minis in the past but I really want to keep this one simple.

I have a 12G295 Head already and a stage one kit that was fitted to a 998 before and an HS4.

Any advice on ignition set-ups? and final drive ratios?

[Stevemcmaster]

Hey there..

Not personal experience, but I seem to remember reading an article in one of the mags on a supercharged 850 which had been based on / was a refurbishment of a period modification.

Will try and dig it out..

Ta
Steve

[anonymous-user]

That would be great see if you can dig the Artical out.. thanks.

[Cooperman]

FullofBeans said:

Thanks for the info!

I have had many Minis in the past but I really want to keep this one simple.

I have a 12G295 Head already and a stage one kit that was fitted to a 998 before and an HS4.

Any advice on ignition set-ups? and final drive ratios?

With regard to ignition, if you are keeping the standard dizzy you could try 5 deg BTDC as an initial setting, then advance it a bit until it 'pinks' and back it off 2 degrees from that.
The diff at 3.76:1 is probably about right for the low torque of an 850.
They are grand little engines and with the 295 head (do sort out the comp. ratio) and HS4, assuming a Kent 256 cam, I would guess you could be looking at around 42 to 44 bhp at the flywheel. It would need to go onto a rolling road for best settings, although the 850 is such an easy engine it's possible to get quite close youself. I don't know which carb needle would be best, but a look in Vizards would give you a good idea.