I know this has been discussed before , but I couldn't find it . What mods do I need to do to the 850 block to fit an 1100 crank into it and how far can the 850 block be safely bored to . I want to keep the original 850 block looking stock but want more power

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1965 Morris 850
1966 Morris Mini Minor
1967 Morris Cooper 'S'
1977 Leyland LS

I fitted a 1098 crank to 3 motors back in the 60s.
It involved machining each side of the centre main block web and cap by .062".
Whilst keeping the thrust washer recess depths.
Also removing .085" from the end webs for crank clearance. This was when 998 or 1098 blocks cost money and I had the machining setup to do it.
You could narrow the crank webs instead but this will weaken it.

These days, I'd save yourself all the grief, fit another block. 998 or 1098.

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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.

Google AC Dodd, as he was doing one of these recently.
Looks like he is aiming for 1150cc, with an increase in stroke and bore.

is there any obvious external difference between the blocks?

other than the engine number stamping....

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did I tell you that I won a trophy?

850 block has 850 cast into the back where the 1275 etc badge goes on other blocks.
From the front, no way to tell.

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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.

Hi AJ
I'v done a few of these mods now apart from machining the centre main down and the two end bearing caps as well as the block the four corners of the block have to be machined away to clear the counter weights.
The one I just finished was 1100 pistons +40 202 head my valves 266ss cam and 2 1 1/4su's on the dyno it went well made just over 80 hp, but the thing that was interesting was he wanted to run the 997 cooper air cleaners (after market) they really killed the HP could not pass enough air through them.

Hi SIMON
They also have 850 cast on the side of the block.
Graham russell

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"It's better to be not informed than ill-informed"

And with M needles can achieve great MPG , what needles did you use GR ?

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That's why it's good to be.............ME

Thanks for the replies guys .

Hi GR what is the cost to machine the 850 block ?

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1965 Morris 850
1966 Morris Mini Minor
1967 Morris Cooper 'S'
1977 Leyland LS

It is important to note , a lot of 998 1098 blocks are much thicker on the bottom of the block,
where it bolts to the gearbox.

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" A Hundred Years From Now It will not Matter what my Bank Acount Was,
The Sort Of House I Lived in, Or The Kind Of Car I drove ... But The World May Be A Better Place
Because I was Once Important In The Life Of A Child"

HI AJ
To machine the block $350, what I failed to say was the sides of the block where the conrods go round has to be ground away
as they hit.
Graham Russell

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"It's better to be not informed than ill-informed"

And once done, the conrods will probably hit the gearbox casing on an 850 box. More grinding to clear.

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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.

Depending on how original you want it to look, you could bolt a later 4 synchro box on with the 850 diff and gear lever.
I have a 1100S in my 850 with this combination so it looks original inside the car.

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Find a job you love and you will never have to go to work !

Thanks for all the info , looks like a bit of a challenge

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1965 Morris 850
1966 Morris Mini Minor
1967 Morris Cooper 'S'
1977 Leyland LS