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 Post subject: MK2 Cooper S rod size
PostPosted: Thu Nov 05, 2020 10:32 am 
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848cc
848cc

Joined: Sat Oct 03, 2020 4:03 pm
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Hi members

I have done a bit of googling but still a bit sketchy on the conrod query I have.

I have my original MK2 Cooper S motor being re-sleeved etc at engine machinists.

Turns out that my original S rods have had the gudgeon end oversized for fitment of non mini std pistons. Rather than stuff around machining and bushing I will just put some other rods in. So the question is is there any difference between mini rod sizing? I have a few complete 1275's as spares if needed otherwise will buy some replacements.

Not sure if it worth going to lighter rods as they are expensive or just find some standards. Are the lightened rods worth the cost (about $900). I am fitting a kent 266 and twin 1 1/2's.

Thanks
Richard


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PostPosted: Thu Nov 05, 2020 12:23 pm 
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Joined: Wed Sep 08, 2004 9:27 pm
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Location: Wodonga - Vic/NSW border
There are 2 big end sizes, 1.5" and 1.75" - Cooper S and early 1100S motors were 1.5" and used the same rods, the rest are 1.75" and there are a couple of different types of rod

If your other 1275s are 1100S type, then there's a good chance that one of them has Cooper S type (AEG521) rods. You can see the difference without removing them from the engine by the shape of the big end cap. If the engine is a 12YTA prefix and the big end has a massive lump of steel on it, then it's a large journal, otherwise the cap is scooped out and it will be a small journal with S type rods

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PostPosted: Thu Nov 05, 2020 12:59 pm 
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848cc
848cc

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Thanks Simon really appreciate the info.


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PostPosted: Fri Nov 06, 2020 6:01 am 
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Oh dear, worry, worry...

Joined: Fri Jun 19, 2009 5:31 pm
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Location: North Rocks
Hi Simon
The Cooper S and the early 1100 S were 1.5/8 not 1 1/2.
Graham Russell

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PostPosted: Fri Nov 06, 2020 10:48 am 
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Location: Wodonga - Vic/NSW border
GR wrote:
Hi Simon
The Cooper S and the early 1100 S were 1.5/8 not 1 1/2.
Graham Russell


bugger, it felt wrong when I typed it but I couldn't remember... what's 1/8" between friends anyway..

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PostPosted: Fri Nov 06, 2020 11:10 am 
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1275cc
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Location: Brisbane
and you can get AEG 177 rods as well. Same size as the 521 and 625.

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