21 replies to this topic

[wreckitralph]

its 70k miles seized where damp got in the bore[being used as a spares car took the carbs exhaust and 1 spark plug] a spark plug  really ..... would like to keep it as its the original lump but 850,s are painfully slow on a sensible budget at home what can be done

Edited by wreckitralph, 11 October 2019 - 09:49 PM.

[GraemeC]

+0.100” over bore, nice torquey cam and if you want to push the boat out a supercharger.
Can be lots of fun from a very smooth and revvy motor.

[wreckitralph]

thanks for the reply would that be  reliable then with those mods   

[Minigman]

The limitation with 850s is the crank won’t rev much above 6k which is where any proper power would be on the engine.

It’s not easy to get decent pistons either and most that you can find will have split skirts and don’t lend themselves to a good compression ratio.

You can put twin HS2 or HS1 carbs on, a 12G295 head )although getting a compression ratio above 9:1 will take some serious skimming).

Other than that it’s the usual ‘stage 1’ stuff.

I tried for ages to find a special tuning crankshaft which would enable the engine to rev reliably but after 18 months of looking gave up and went with a 1098.

The other thing you’ll need to do to fit a half decent cam is to have the block line bored for cam bearing install. The cam runs on the cast block normally. Any half decent cam will cause significant wear on the block.

Good luck.

[ACDodd]

Make it bigger, 1150cc is a realistic option, as is 70bhp/70lbft.

Ac

[Cooperman]

The 850 should be regarded as the true 'classic' Mini. It was the original and was what set the car out from the rest of the small cars of the early 1960's.

In fact, they are a joy to own and drive, giving the real 'retro-driving' experience from that time.

'In the day' a lot of 850's were improved and the above advice is good.

A nice specification would be:

A 295 head well gas-flowed & skimmed to give the best possible CR which is around 9.5:1. Better pistons if you can find a set, a Kent 256 cam, a 3-into-1 exhaust manifold with a 998 Cooper exhaust pipe, a pair of HS2 carbs, or a single HS4 on  aflowed and matched inlet manifold, a slightly lightened flywheel. 

Have it all balanced and keep the revs below about 6200 rpm to preserve the crankshaft.

With all that you should be getting somewhere near 50 bhp at around 5600 rpm and with that the old 850 will go very nicely.

[wreckitralph]

i didnt realise when i got my project but i also included the other mini wich is here and thats a 79 850 mini city hence the question regards the engine i got it off a mate as stated elswhere on the forum my mate is working away hasnt got the time for a project for the foreseeable future so hes going to buy a mint  1275gt as hes going to be earning some good money  ive bought 1 got 1 free kinda thing but need to collect it and find storage as the shed here is only big enough for 1 and theres a shell there

Edited by wreckitralph, 12 October 2019 - 09:16 AM.

[mk1leg]

i tuned an 850 back in the late 70s max rebore new pistons, crank regrind and coated, 731 camshaft stage 2 head LCB system twin 1.25 carbs it pulled like a train loved it as my first dabble into tuning an engine myself 

[Spider]

Money wise, IMO, the best option here is to take it out and fit a bigger engine. A 998 or if you can find one, a 1098 in standard form will make your driving experience much more pleasurable, while retaining good reliability and being easy to look after.

[wreckitralph]

Money wise, IMO, the best option here is to take it out and fit a bigger engine. A 998 or if you can find one, a 1098 in standard form will make your driving experience much more pleasurable, while retaining good reliability and being easy to look after.

 

i do have a 1100 motor here allegedly tuned with 1071 bits in it but i dont know and wouldnt know what i was looking at to be honest 

Edited by wreckitralph, 12 October 2019 - 07:50 PM.

[timmy850]

I’ve just put a 1098 in my Morris 850. Apart from the engine number there really isn’t much visually different compared to an 850.

The 1098 fitted to minis here had 50hp stock, which is a huge improvement over a stock 34hp 850

Edited by timmy850, 13 October 2019 - 03:34 AM.

[Minigman]

I’ve just put a 1098 in my Morris 850. Apart from the engine number there really isn’t much visually different compared to an 850.

The 1098 fitted to minis here had 50hp stock, which is a huge improvement over a stock 34hp 850

I did the same thing having given up looking for nice 850 bits. Hard to tell the difference. Even run the 850 engine number on it.

[jomaoliveira79]

Unless you want to spend serious money (see the spec of Mini Minor featured on Jay Leno Garage YouTube channel) you should get a 1098 as externally they are the same.
Properly performance parts are scarce or must be custom built.
I struggle in modern traffic with my standard 850 (despite being properly tuned) and decided leaving it be and purchased recently a Clubman 1098 to get a more satisfactory speed...

Edited by jomaoliveira79, 14 October 2019 - 12:09 PM.

[mab01uk]

You might like this OAP 850 engine spec in link below........

 

Shorrock supercharged 850, bored +087 to fit Mini Se7en Omega pistons (908cc) 
515 crank
Properly modified 998 rods
OAP 265/360 cam
295 head
 Showed 90hp on KAD dyno but reduced boost and ignition to give 75hp as it was on std 3 syncro box.

http://www.theminifo...-850/?p=3341026

 

Edited by mab01uk, 14 October 2019 - 03:33 PM.

[Cooperman]

I did once put an MG1100 engine into an 850 which my wife owned. It still had single leading-shoe drum brakes. It sure went, but didn't like stopping.

One of our young apprentices wanted to buy it, so I sold it and bought a 997 Cooper fitted with a 1275 'S' engine. I soon fitted the bigger 7.5" brakes though.

Personally I think an 850 has a charm of its own. Sure it is slow, but it is a true Mini classic and a 'car of its time'.