ausmini :: View topic - how big can you go with a 1275?

1380cc or 73mm bores is about as big as you can get with a 1275. The walls will be quite thin at that stage. Zack is getting confused with stroking the crank which essentially you grind the crank to get more piston travel which increases your swept area which which will give you more CC's such as 1400, 1410 etc. Not the same as overboring further which is making the clyinder diameter bigger.

1380cc's are theoretically and practically as far as you can go without spending mega bucks for custom larger pistons. The only other step I can think of is sleeving the block with inserts ($$$ per cylinder...)

If looking for a block to rebuild, the less meat taken off the better (ie. 1275cc exactly is ideal).

Author:	Smarty [ Mon May 14, 2007 12:17 pm ]
Post subject:	how big can you go with a 1275?
Hi guys I am looking at buying a mini with a 1380cc engine. When it comes time to rebuild it would I need a new block? Regards Smarty

Author:	1360 LS [ Mon May 14, 2007 12:38 pm ]
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Depends on the condition of the bore if I'm not mistaken as well as the general condition of the motor. Most 1275's should be ok up to 1400 or so.

Author:	Smarty [ Mon May 14, 2007 12:40 pm ]
Post subject:
oh okay so it could possibly go another rebuild, all things being in good order.

Author:	1360 LS [ Mon May 14, 2007 12:43 pm ]
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Yea but others on here will be able to give you a better idea but thats the basics of it all

Author:	1018cc [ Mon May 14, 2007 12:52 pm ]
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I have definitely heard of a 1425cc A-series engined mini before but I'm not sure if they had wierd pistons with shallow deck heights or they took it out really far (0.100" etc). Worst case senario is get the block sleeved.

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Author:	Lillee [ Mon May 14, 2007 12:53 pm ]
Post subject:
1380cc or 73mm bores is about as big as you can get with a 1275. The walls will be quite thin at that stage. Zack is getting confused with stroking the crank which essentially you grind the crank to get more piston travel which increases your swept area which which will give you more CC's such as 1400, 1410 etc. Not the same as overboring further which is making the clyinder diameter bigger. 1380cc's are theoretically and practically as far as you can go without spending mega bucks for custom larger pistons. The only other step I can think of is sleeving the block with inserts ($$$ per cylinder...) If looking for a block to rebuild, the less meat taken off the better (ie. 1275cc exactly is ideal).

Author:	1018cc [ Mon May 14, 2007 12:58 pm ]
Post subject:
Lillee wrote: 1380cc or 73mm bores is about as big as you can get with a 1275. I thought that the bore diameter was 73.5mm with a 1380cc?????? I'm probably wrong as all I have to worry about is a 998.

Author:	willy [ Mon May 14, 2007 12:59 pm ]
Post subject:
Lillee wrote: 1380cc or 73mm bores is about as big as you can get with a 1275. The walls will be quite thin at that stage. Zack is getting confused with stroking the crank which essentially you grind the crank to get more piston travel which increases your swept area which which will give you more CC's such as 1400, 1410 etc. Not the same as overboring further which is making the clyinder diameter bigger. 1380cc's are theoretically and practically as far as you can go without spending mega bucks for custom larger pistons. The only other step I can think of is sleeving the block with inserts ($$$ per cylinder...) If looking for a block to rebuild, the less meat taken off the better (ie. 1275cc exactly is ideal). 73mm is 94 thou is 1360cc. 73.5mm is 1380cc. Then once you've done that and aren't satisfied you can start to looking at stroke... that's where the fun begins

Author:	DRB33N [ Mon May 14, 2007 1:20 pm ]
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1460cc, but then thats where it comes down to mega $$$$ and starts becoming unrealiable.

Author:	drmini in aust [ Mon May 14, 2007 1:34 pm ]
Post subject:
IF you can find a set of Omega etc 74.0mm pistons still, it will give you 1400cc with standard stroke. Some people have been lucky and offset bored blocks to 74.7 and fitted Triumph 2.5PI pistons, that gives 1426cc. Block is very thin, not many bore that far successfully. You have to mill a big chunk off the top of the block too, as these pistons are real short.. IMO once it gets to 1380 maybe 1400 (I'm talking standard stroke) and becomes worn, it's time to find another block. It's possible to sleeve them back to 1275, but costwise hardly worth it.

Author:	Smarty [ Mon May 14, 2007 1:51 pm ]
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so how much should I pay for another block?

Author:	drmini in aust [ Mon May 14, 2007 2:05 pm ]
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If just a 1275 (non-S) you should find a block and bearing caps, with a few rebores left, for $200 or so. NEVER buy a bare block with no caps, they are not interchangeable- caps were line bored with the block when made.

Author:	mattywood [ Mon May 14, 2007 2:10 pm ]
Post subject:
Vizard reckons if you have the space you can take them to 1600cc

Author:	DRB33N [ Mon May 14, 2007 2:17 pm ]
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mattywood wrote: Vizard reckons if you have the space you can take them to 1600cc That would be one very hot running engine, keeping it cool would be a bastard and if you were to spend the money going to those extremes my vote would be on engine conversion for the same cc.

Author:	rehab1964 [ Mon May 14, 2007 2:29 pm ]
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a friend of mine has an A40 Farina that he does hill climbs in, last I saw him he was showing off his new a series motor - taken out to i think from memory 1440 - the cylinder walls were incredibly thin, I'm not sure how it would go for cooling or longevity but I bet it'd be fun in the meantime

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