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It would have to be a missprint, .300oversize in a small bore block is not possible.

998/1100 cranks fit into a 850 block but the thrust surfaces in the block need to be widened to allow for the larger thrust washers.

Henry Draper, former owner of Northern Mini Parts here in Melbourne built a 1960 "Mini Minor" to complete in the under 1lt historic class at Targa Tasmania. The car had to retain all its original components but engine internals were open so a early 850 block was used, with a A+998 crank, rods,pistons, the cam tunnels were line bored and bearings fitted, the 850 head was modified, roller rockers fitted, the gearbox was a s/c 3 syncro gearset in the early case with the straight wand gearlever. It bet every other Mini in the rally, including big bore xflow powered cars, and at one point was 12th outright, putting Porsche's, WRX's, GTR's etc to shame. Henry competed in the Rally for 12 years in a row, and used the same car/engine each year.

Henry was always a 'Top Runner'. He knew his stuff.

It's a misprint, should be 1100 not 1200 and 1098 crank not 998 crank.

Released by Oselli in the mid 60's as a stroked/overbored 850 half engine.

850cc block bored to 64.58mm, machined to take a 1098cc crank (tuftrided), additional cam bearings, tuftrided floating pin rods, lightweight balanced pistons and heavy duty bearings.

Also available as a complete engine.

As above plus fully balanced crank and rods, road/race camshaft (I think 997 Cooper) and a GT cylinder head (10.2:1 CR).

Praised by various magazines of the time.

doctor jon wrote:It's a misprint, should be 1100 not 1200 and 1098 crank not 998 crank.

Released by Oselli in the mid 60's as a stroked/overbored 850 half engine.

850cc block bored to 64.58mm, machined to take a 1098cc crank (tuftrided), additional cam bearings, tuftrided floating pin rods, lightweight balanced pistons and heavy duty bearings.

Also available as a complete engine.

As above plus fully balanced crank and rods, road/race camshaft (I think 997 Cooper) and a GT cylinder head (10.2:1 CR).

Praised by various magazines of the time.

Now we're getting somewhere

Sounds good. That 997 cam crops up all over 60's tuning by the looks of things.

997 cam shows up, because it was a really good cam.

Thought! Why would you go to all the trouble of boring an 850 block with only one cam bearing and modifying it to take an 1100 crank when you could just use an 998/1100 block when you have gone looking for the 1100 crank anyway?

ivor badger 2 wrote:997 cam shows up, because it was a really good cam.

Thought! Why would you go to all the trouble of boring an 850 block with only one cam bearing and modifying it to take an 1100 crank when you could just use an 998/1100 block when you have gone looking for the 1100 crank anyway?

I suppose the kit used new parts as the 1100 crank would have been available off be shelf and the customer retained the existing engine. Must have been cheaper even given the machining than also supplying a new block/short engine.

If I were to do this is quite like to retain an 850 block, 850 engine number and all that stuff. I've not ruled it out yet.. 850 sleeper.

Was about 1970, bought an Austin 1100 engine from breakers yard, rebuilt it with new oil pump, piston rings bearing shells, Duplex timing gears etc. etc. Managed to get a 12G295 head to replace the 12G202 that was fitted. A single SU HS4 reverse carb was used. Replaced bits in the gearbox including changing the final drive to 3.44:1 ratio.

This lot was fitted to my 1962 Mini. Ran extremely well, would maintain 100 MPH on the motorway quite easily. Was not bad on fuel too. The car was used regularly and this power unit remained in the car untouched for about 26 years. It was only removed because my sister in-law managed to wreck the gearbox when she borrowed the car.

GS Davies
I think you will find that it's 998 block, fitted 1100 crank , Hillmam Imp pistons , offset bore , as I remember it came out as around 1150 cc, this was mentioned sometime ago on the forum, the Imp pistons ar short skirt type and slap about and the engine will burn oil , top of the block needed to have x amount removed, the reason they never used the 998 crank was because the vast amount needed to be removed of the top of the block you would break through the water pump bolt holes!!! , the down side of the 1100 crank is it's long stroke ,sustained high rev and it would destroy itself, as mentioned earlier cooper s engine were expensive , no morris / austin 1300 about , but plenty of 1100 to play with ,Oselli would take 850 in part ex and is probably were you are getting mixed up, local to was ,Piston supplies ,Worksop and Stanwoodhunter, Bawtry that did this conversion , and probably Arnetts , Doncaster .
Goff

Oselli didn't offer the 1216cc (imp pistons and 1098cc crank) engine in the mid 1960's.

The 1100cc engine was based on the 850cc block (I had one many years ago), probably because at the time 998/1098cc blocks were not very common, whereas the 850cc block was.

When 998/1098cc blocks became readily available these were used instead of the 850cc block (less work involved).

In 1970 the 1100cc half engine (OE 1125) was £49.00, the 1100cc complete engine (OE 1125 GT) was £130.00

You could buy an exchange block, overbored complete with pistons for between £19.00 - £22.00.

850cc bored to 950cc
948cc bored to 1050cc
997cc bored to 1100cc
998cc bored to 1050cc
1098cc bored to 1150cc

goff wrote:<SNIP>fitted 1100 crank , Hillmam Imp pistons , offset bore ,
as I remember it came out as around 1150 cc,
this was mentioned sometime ago on the forum<SNIP>

Goff, it was also mentioned on page 1 of this thread, about half way down!

"Here's one I made earlier". (About 1988)
Ian

ianh1968 wrote:

goff wrote:<SNIP>fitted 1100 crank , Hillmam Imp pistons , offset bore ,
as I remember it came out as around 1150 cc,
this was mentioned sometime ago on the forum<SNIP>

Goff, it was also mentioned on page 1 of this thread, about half way down!

"Here's one I made earlier". (About 1988)

HillmanImpPlus30.png

Ian

What block was that in?

ianh1968 wrote:

goff wrote:<SNIP>fitted 1100 crank , Hillmam Imp pistons , offset bore ,
as I remember it came out as around 1150 cc,
this was mentioned sometime ago on the forum<SNIP>

Goff, it was also mentioned on page 1 of this thread, about half way down!

"Here's one I made earlier". (About 1988)

HillmanImpPlus30.png

Ian

A lovely job. but one question and not trying to be critical or demeaning. Why would you go to that amount of effort, when you can go to any scrap yard and buy a 1275 which has a stronger crank and rods by 1988?

I think it's fascinating to see alternative ways of getting extra power, especialy if some of these road test results are to be beleived. The Vic Derrington conversion on the 850 that used a Weber sounded like it went like a scalded cat!

Obviously back in the 60's it wasn't as easy to come by a 1275 engine, now of course that seems to be the default option since they were used in Metros and every Mini from the early 90's.

In my case, I'd interested in building a 'period modified' car using some of these old techniques. Just putting a 1275 A+ in it feels like cheating and doesn't set it apart in any way.

gs.davies wrote:What block was that in?

The block was a normal 998/1098cc block. There is reference in the
Vizard book that some of the early 1100's were bored out 850's
anyway, so I felt that it was a valid contribution to the discussion...

ivor badger 2 wrote:Why would you go to that amount of effort, when you can go to any
scrap yard and buy a 1275 which has a stronger crank and rods by 1988?

Well, this particular engine was my Dad's, as I said before.
He built it in the late '60's for his then brand new 1966 MiniVan.
Initially it was 1216cc and it was still 1216cc when the same
engine was transplanted into a 1963 saloon shell in about 1980.

After that, it got "archived" in the loft until 1988 or thereabouts when
I dug it out and decided to rebuild it for sentimental reasons.
(And my 998cc Cooper engine had just blown up...)

There were enough bits in the "kit" to make a whole engine and it only
needed a straight rebore because the offsetting had already been
done. With a new set of +0.030" pistons it then became 1242cc...

With a seriously modified 12G295 head on it and an MG Metro cam
and some other bits and pieces, it went quite well. The original cam
was the venerable 997 Cooper cam that Ted Wong from this forum
bought from me a few years ago...

gs.davies wrote:Obviously back in the 60's it wasn't as easy to come by a 1275 engine

This was exactly the thing. People used what they could get and
were very innovative. Early large bore conversions involved
using Triumph 1300 pistons to make 1385cc from 73.65mm
(2.9", in English) and Simca 1200 pistons at 74mm to make about
1399cc. The real "biggy" was to use the Triumph ?2.5 Litre? 74.7mm
pistons and make something around 1430cc with standard crank.

Looking at my photo, it might have been possible to squeeze
in the 1300 pistons, but there would still be the oilway issue
to contend with.

Never say never...

Ian

doctor jon wrote:Oselli didn't offer the 1216cc (imp pistons and 1098cc crank) engine in the mid 1960's.

The 1100cc engine was based on the 850cc block (I had one many years ago), probably because at the time 998/1098cc blocks were not very common, whereas the 850cc block was.

When 998/1098cc blocks became readily available these were used instead of the 850cc block (less work involved).

In 1970 the 1100cc half engine (OE 1125) was £49.00, the 1100cc complete engine (OE 1125 GT) was £130.00

You could buy an exchange block, overbored complete with pistons for between £19.00 - £22.00.

850cc bored to 950cc


948cc bored to 1050cc
997cc bored to 1100cc
998cc bored to 1050cc
1098cc bored to 1150cc

Doctor Jon thanks ,
So was the Oselli 1125 engine just say + 60 on standard pistons?????.
Was the 850 out to 950 done using the A40 pistons???????

I always thought the imp pistons took it out to around 1150, wrong again

Ian that's a nice nostalgia engine you have , I would think theirs more laid about in people garages, just shoved in a corner waiting to be uncovered,Ian you can do the conversion using a 998 crank , though you would be on the limits , when the top of the block is machined , using surface grinder DO NOT REMOVE THE AREA WERE THE ENGINE NUMBER IS ,AS THATS A BOLT HOLE FOR THE WATER PUMP. So that leaves you 3 good bolts , the one that you would break into , either put a stud in braze it up and resurface or braze it up and tap for smaller bolt, I HAVE SEEN ONE OF THESE DONE !
You hit the nail on the head with your first posting, S engines expensive for the ordinary working man , no Morris/Austin1300 but plenty full of the 1100 including the MG version coming in the scrap yards.
Goff

goff wrote:Ian that's a nice nostalgia engine you have<SNIP>

Had, rather...

It had numerous "blow-ups", mostly head gaskets, but this one was quite major... Top Tip - This is what happens if you rev these up past 7000rpm
on a bog-standard crank. Either keep the revs down, or get a
tuftrided crank, or do both...

... and when it died in battle against an Astra GTE,
this was the problem... This was all happening in my pre-dyno days...
I'm not sure what the problem was, but it was more than likely
a bad needle choice, or else the timing was wildly out.
(Maybe I had it at 16 degrees at 1200rpm and hoped for the best,)
(as per some instructions found elsewhere on this site!)

After this, I built a 1380cc engine, but some of the bits from this
1098/Imp/1216/1242 engine lived on...

The head ended up on another 998cc "Cooper-Type" engine that my brother had.
The crank was much later fitted to a standard 998cc engine to make it 1098cc.
The original MG Metro cam for it ended up in my Dad's "MG1330 Allegro" engine.
The later MD276 cam was sold on eBay...
The SCCR 3Synchro kit was sold on eBay to a "Historic Racer" in Norway...

ianh1968 wrote:

goff wrote:Ian that's a nice nostalgia engine you have<SNIP>

Had, rather...

It had numerous "blow-ups", mostly head gaskets, but this one was quite major...

1100CrankBroke.png

Top Tip - This is what happens if you rev these up past 7000rpm
on a bog-standard crank. Either keep the revs down, or get a
tuftrided crank, or do both...

that's where they normally break, even S ones. In the dim and distant past BMC/BL used to offer a crank exchange service, but of course would not take broken cranks in exchange. One could always resort to a large clamp and an arc welder with armex rods.

All I know is the 850 crank don't fit in a 998 block gave it a try

Journal at crank tail end is to wide
Centre journal is to wide
Front journal is right

Need double thickness thrust washers

Also when torqued down crank wouldn't roated so I'll say they are abit thick on the journals

ianh1968 wrote:
It had numerous "blow-ups", mostly head gaskets, but this one was quite major...

1100CrankBroke.png

Top Tip - This is what happens if you rev these up past 7000rpm
on a bog-standard crank. Either keep the revs down, or get a
tuftrided crank, or do both...

(I hope the photo of the busted crank attaches here)

If you look at nearly all bust Mini Cranks, they nearly all let go in the same place, 998, 1100 and 1275's.

Proper attention to harmonics, resonance and appropriate treatment avoids these problems