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Cooper Vs Non Cooper Engine Differences


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#1 spiguy

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Posted 09 April 2019 - 10:53 AM

Hi All,

 

Bought an engine to build up. My current car is a 92 Spi cooper. My plans for it were to change head and cam to Calver provided parts, however I then decided rather than have the car off the road too long, to buy a 2nd engine, get it ready then do a swap. Seems like a good idea to have a spare anyway!  I ended up with a 1275 carb engine and box, however being a later engine it has the crank sensor hole as by that time the SPi was being fitted to the cooper variant, so should be fine for my SPi. This 'new' engine is a non cooper engine. I have always been of the belief that the difference between cooper and non cooper 1275's of this era is different head to up the compression  / perhaps different valves (not sure) and different cam.

 

Is this correct?  mainly, are the bottom ends the same ?  I was thinking that as I am changing cam and head, it does not matter that the 'new' engine is not a cooper, but I have seen elsewhere something that suggests that maybe the cooper vs non cooper, has different pistons?

 

So basically the question is, what are the differences and if I fit uprated head and cam as advised by Calver, is there anything else I need to change on the 'new' engine, with regard to it being a non cooper engine? Is there something else that gives the difference in compression ratio for example (9.4:1 vs 10.1:1 if I recall, numbers may be a little out)

 

Cheers

Craig



#2 DeadSquare

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Posted 09 April 2019 - 11:11 AM

If you are buying bits, or having work done through Calver, he will put you right on these details.



#3 spiguy

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Posted 09 April 2019 - 12:54 PM

Yup, he's very helpful with information. I still just wanted to know though if there are differences between the bottom end of a 9.4:1 non cooper and a 10:1 cooper engine. Will be a couple weeks before I call him.

 

Cheers

Craig



#4 spiguy

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Posted 09 April 2019 - 01:03 PM

Found this on wikipedia - suggests they are the same block / pistons no? - EDIT - ignore me, I am stupid. It just says they are the same bore and stroke

 

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Edited by spiguy, 09 April 2019 - 01:05 PM.


#5 nicklouse

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Posted 09 April 2019 - 01:21 PM

the main issues you will have is the ignition triggering system but that can be sorted .

the MPi does have a different casting as it mounts the accessories on differently.

 

otherwise there is no difference.



#6 spiguy

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Posted 09 April 2019 - 02:26 PM

Hi Nick,

 

Thanks. No issue on ignition triggering, the 'new' engine has the later transfer housing with the crank sensor mounting hole on it. I'm afraid engine stuff is all a bit new to me, so a little confused. The 'new engine, being from a non cooper 1275 is 9.4:1. It has 21962 pistons and I believe my cooper one has 21963 pistons?  does this influence the head I buy in any way?  If I buy a calver GT head for the SPi cooper, is that suitable for the new engine as well, even though it is a lower compression engine?  I don't really understand how it all works (piston, head chamber etc).  Do you specify the pistons that are to be used with the head ?  If so and I specify the new engines pistons (21962) then I wondered whether I would still be able to use the new calver head on my current engine if in future I needed to swap it back in (e.g. if say I blew the bottom end on the new one - my current engine will be my spare). Hope that all makes sense!

 

Thanks

Craig






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