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1100 Crank Into 1275 Block


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#1 dunk69

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Posted 13 February 2020 - 03:50 PM

hi, can anyone answer this conundrum......

will an 1100 crank fit into a 1275 block? i'm not scared of engineering work and modification.

i blew the block of an 1100s engine that i had in a clubman, now my 1275 is out and on the bench i'm thinking of building it with the 1100 crank as i relly liked the torque of the 1100

will it fit though? are the bearings different and are the piston sizes going to be a struggle

thanks

 

1979 mini clubman estate with a 1275 gt lump



#2 nicklouse

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Posted 13 February 2020 - 05:08 PM

If a UK 1098 then there are too many differences to make it viable. 



#3 Ethel

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Posted 13 February 2020 - 05:25 PM

You'd be better off making a stroker out of a 1275 by using S rods. It wouldn't be cheap & the 1275  would already be better than the 1098.



#4 Moke Spider

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Posted 13 February 2020 - 06:46 PM

There's a few different 1100 engines and all very different. So we can be all on the same page here, can you post up the Engine Number Prefixe of the one you have ?



#5 mini13

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Posted 14 February 2020 - 10:31 AM

1100 is going to be a small bore in which case it's a no go.

The only exceptions are putting in the 1071 S crank ( sometimes known as 1100 especially if it's at +20 bore), or the south African 1100 crank. Both if these are short stroke, so sound like the opposite of what your trying to achive

#6 Cooperman

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Posted 14 February 2020 - 02:42 PM

Best bet is to fine a 999 bllck and use the 1098 crank. If the block is bored right out to +80 thou it will have a capacity of around 1180 cc and will give fantastic torque, especially if you use something like an Evo001 cam.

#7 dunk69

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Posted 15 February 2020 - 10:17 PM

ok, firstly, thanks for the responses everyone, really appreciate it.....

so, to take it from the top.....

nicklouse, it is a uk crank, came out of a '79 clubman 1100. so you think there's just too many variables to make it a viable option? it'd be going into a uk 1275 gt block. but i have to say, i'm leaning towards your opinion. looking like its not really doable.

Ethel, t sounds like you're suggesting that i could achieve a similar result by using different rods instead? so do you mean that a slightly longer rod would fit and give me a torque increase rather than trying a longer stroke crank?

Moke spider.... i don't know the prefix of the crank, it came out of a 79 clubman that i cracked the block of, that was about ten years ago, i scrapped the block but kept the crank hoping to use it someday. it was a uk car on its original engine though. then i wrote the car off a year later so i don't have any of the paperwork or corresponding numbers for.

Mini13, yeah it is definitely a uk 1100 crank, so are you saying that it just wont go into a 1275gt block? too long a stroke perhaps? so a deck height issue?

Cooperman, i already have a 1275 block to use, in fact i have 2 identical blocks to choose from, i was hoping that the 1100 crank would fit and give me a little bit of extra displacement and a torque increase. i also already have a road/rally cam in the block ( a mid-range BL special tuning cam) like i said, i was hoping the crank would be a fairly straight forward swap in.

i guess the 2 main points i need to answer are.... 1: would the stroke of the 1100 crank fit without a deck height problem, and 2: would the crank and block be a viabke fit where the journals are concerned.....?

thanks everyone.



#8 nicklouse

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Posted 15 February 2020 - 10:24 PM

Ok ain’t happening.



#9 dunk69

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Posted 15 February 2020 - 10:26 PM

Best bet is to fine a 999 bllck and use the 1098 crank. If the block is bored right out to +80 thou it will have a capacity of around 1180 cc and will give fantastic torque, especially if you use something like an Evo001 cam.

 

thanks, second post on this

1100 is going to be a small bore in which case it's a no go.

The only exceptions are putting in the 1071 S crank ( sometimes known as 1100 especially if it's at +20 bore), or the south African 1100 crank. Both if these are short stroke, so sound like the opposite of what your trying to achive

 

thanks, second post on this

 

There's a few different 1100 engines and all very different. So we can be all on the same page here, can you post up the Engine Number Prefixe of the one you have ?

 

thanks, second post on this

 

You'd be better off making a stroker out of a 1275 by using S rods. It wouldn't be cheap & the 1275  would already be better than the 1098.

 

thanks, second post on this

 

If a UK 1098 then there are too many differences to make it viable. 

thanks, second post on this



#10 dunk69

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Posted 15 February 2020 - 10:27 PM

Ok ain’t happening.

yeah it looks that way. shame though. ah well



#11 timmy850

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Posted 16 February 2020 - 08:25 AM

The difference is pretty minimal anyway, only a couple of mm difference in stroke from a 1098 to 1275.

1275 will always make more torque/power as it’s got a bigger bore and better head

#12 Ethel

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Posted 16 February 2020 - 11:22 AM

Bog standard 1275's have bigger big end journals than "S" engines - so you can increase the stroke by offset grinding the journals to S size and using S rods.

 

I think we're all on the same page in saying you'd get better results for your money by just reboring either engine along with the usual head work cam swaps etc.



#13 dunk69

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Posted 16 February 2020 - 07:26 PM

The difference is pretty minimal anyway, only a couple of mm difference in stroke from a 1098 to 1275.

1275 will always make more torque/power as it’s got a bigger bore and better head

yeah thats true. but the difference in torque characteristic in the 1100 was very noticeable. the way it used to get out of corners was something special. was hoping to combine that with the 1275 block size



#14 dunk69

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Posted 16 February 2020 - 07:32 PM

Bog standard 1275's have bigger big end journals than "S" engines - so you can increase the stroke by offset grinding the journals to S size and using S rods.

 

I think we're all on the same page in saying you'd get better results for your money by just reboring either engine along with the usual head work cam swaps etc.

now this is very interesting indeed..... so you're effectively moving the centre of the journal out from the centre of the crank and getting a slightly longer stroke. like it!

do you know anyone thats actually done this? is it a very common practice?

i've got a very skilled machine shop that i use who have done lots of really good work for me in the past regrinding and balancing on other types of engine so i'm sure the work wouldnt be a problem.

if you can offer me any more information on doing this at all, no matter how small of a nugget of knowledge i'd be greatful

thanks



#15 GraemeC

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Posted 16 February 2020 - 07:46 PM

Loads of people have done this - known as a stroked crank.

However, you need the earlier 1275 crank NOT one of the A+ ones, due to the way the big end journals are machined.

Then obviously you need con-rods with the Cooper S size big ends.






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