Having wound 850s up to give power way back when most of U lot were but a twinkle in yer old man's eye, I gotta say- bin the block, get a 998/1098 one and start with that.
Yes, you can fit 998 or 1098 cranks into an 850 OK, I used to do this for people way back then- but the bearing width of the mains is different. Machining for this these days will cost you more than a 998 block will. Ditto the machining for the extra cam bearings.

Late 850 cranks have a thicker stronger tail (1.5") than the early ones did (1.375"). But that's not where lots of them broke.

Another problem is pistons. 850s had split skirt ones, these days decent 850 performance pistons are rocking horse dung.

I would start with a 998. You can get pistons now up to 0.100" oversize.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

As I thought, you will spend too much money for too little gain. At the end the results will not be too reliable either... Sounds great but just a money pit and not practical really...

For a relatively similar amount you can build a big block with TWICE the horsepower potential and probably reliability too

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Lillee - 1969 Morris Mini K

but everyone is doing that..

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Obviously..... beacuse its the easier/cheaper/"better power per $$ spent" option

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

Depends what you're trying to achieve...ie. what you call big power.

The only 'performance' mods to my standard bore 848cc MKII are 12G202 head (standard other than skim - cheap as chips), cam, 3-1 exhaust, 1.5" carb with standard design K&N.

It blows away stock 998's and 1098's, with a 0-100 time more around the 997 cooper mark (ie 17-18 seconds compared to a 998's 25 seconds). I'm still running a stock boat anchor flywheel. If I ever pull the engine again the light one on the shelf will go in. Will I blow out a block/cam bearing? Maybe in the long term, but I have 2 more blocks sitting in the shed....in the mean time I'm having cheap, reliable fun. (oh, until I finish the 1380....)

If you can turn a wrench then all up the above can cost less than a 998 in good/reliable condition, and you've got more power. AND you can say it's an 850

that's the point.... I want to make a rocket 850 one day - the 998 crank sounds like a good idea

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did I tell you that I won a trophy?

It's a novel idea and I think it will be fun. But lots of money and potential heartache to tell people that it's an 850 and getting blank looks back at you seems like it's not worth it to me.

I think what Bootesmini has done with a 1275 supercharged in an 850 shell with 850 badges, 850 windows, seems cooler. Then you can say "it's an 850" and still get "Holy crap" performance and pretty good reliability

I want to put the correct Morris Mini 1100 badges back on my car just for that purpose so i can tell people who ask, "wow it's fast, is it an S" with "No it's just a K"

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Lillee - 1969 Morris Mini K

hmmm


Got one...

Got one

Got one

Got one..

hmmm....

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There are not really many practical reasons for a heavily modified 850, except the priceless novelty value. I'd love to say one day:
"Yeh my 850 is MPI, turbod and has all the bells and whistles, sure the power is less than a stocko 1275 but who cares? I'm the only one stupid enough to do it!"

In the mean time I'll stick with my 1275, vented braked Morris 850, if it is ever finished.

oh... it's aaallll novelty...

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Having the fastest car out there has nothing to do with owning a mini now, does it?!

If you're wanting to built a rocket car, are you going to do it with an 850? Hell no. But if you're on a budget, and already have an 850, there's no reason not to have a perfectly perky little motor.

hmmm..........peeeerky.......

Isn't this what the Starlet conversion is all about? Looking stock, but having 200hp? I really wanna do one of those.

I had plenty of fun in my 850 panel van. Pity was that when thrashing it, grandmas in their lil' pulsars were going straight past me. A hottie 998 fixed that 295 head, 731 cam, twin 1-1/4SUs, etc.

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Cheap, Fast, Reliable. Choose two.

That sounds like an awesome idea if you have all the parts I would love to build it it would be heaps of fun and to go all out knowing that if it breaks, it didn't cost the earth.

that would just encourage me to go mental and build something simply for power and not really reliability. would like to see how far someone can get these

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-doing a Degree in Mechanical Engineering,
and a few conversions:
13B Extend in a 1600
4EFTE in a mini ute (all slowly)

hahaha, LOVE IT


anyway, they modified the &*$# outta these way back before the Cooper hit the "scene"
so ya, go the SPORTS 850!!

I've been watching all this with interest , a few points from my ideas - WHY , Why not , I'm planning on having some fun with the very sad 850 that's currently in the sports850 once I have the replacement 850 ready to go in . Sitting around (here and in my other mini shed in another town) waiting for projects a 940 head that's been majorly shaved for a speedway motor (very high compression head on a 1275 will probably be semi high compression on an 850 , well , it shouldn't be less than standard anyway) , yes it will most likely stuff the block by needing pockets cut for the valves but the block has a few other problems anyway so no loss . Somewhere I have an old 649 cam that is most definitely overkill but it's here and worth a shot . It's already got extracors and twin 1 1/4 so the in and out should be reasonable . I doubt the motor will live for very long as it's in it's 3rd car that I know of and had sat idle in a shed for 15 years before I found it and have given it a good thrashing in the sports850 (I bought the sports850 with a tired 1100 in it but the original block came with it and is safely stored ....) , prior to the sports850 we used it in the mini van that dad used to tow the 13 foot tinny with , 850's aren't the slouches people think they are . Ok , getting sidetracked now but basically I am planning to do it for a bit of fun and use some of the bits I already have , cost will probably only be the time with the die grinder and fitting and a 1275 head gasket , bugger all really . It's still several months off but I'll let you know what happens when it's done , and how long it lasts , but should be reaching the limit of efficiency for the capacity , i.e physically getting as much air/fuel in and out as the piston can move very easily .

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