5 replies to this topic

[JimmyB]

Hi

 

I have an engine which has already been bored out to 1330cc that I want to rebuild. I am considering my options with regards to the bores as I understand I can't bore the block out any more than it already is.

 

I have separated the block from the box but I haven't removed the pistons and rods yet. The bores don't look too worn and measure up at an average of 72.14mm in the center of the bore. Would I be able to get away with just a hone and new rings and possibly pistons? The engine was running fine when removed with no visible smoke from the exhaust.

 

Any opinions would be greatly appreciated. I will pull the pistons out at some stage and have a proper look at the bores and pistons at some stage anyway. The crank currently has an end float of 10 thou so it all needs some thorough investigating.

 

James

[Cooperman]

Your best bet is to have the block sleeved back to 1275 and re-build with new 21253 pistons.

Mini Spares sell the correct sleeves and this effectively renews the block which can then later be re-bored to 1293, 1310 and 1330 cc as further re-builds are necessary over the years.

[ACDodd]

Hang on, blocks can be bored to 72.5 and bigger. Sleeve are available to restore from 74mm bores. The first thing you need to do is have a measure up. Then from this point you can decide the way forward. As ever I still offer the free measuring up option for all miniforum members.

Ac

[Cooperman]

Of course they can, but for the cost of offset boring from 1330, it would be better to go back to 1275 and have, effectively, a new block which can then be bored, without any risk, a further 3 times.

Over-size engines are fine for competition where every single bhp or ft.lb. is critical, but for road use there is no advantage, except bar room bragging rights about 'big' engines.

[ACDodd]

The cheaper option would be offsetting, it will cost £350 just to sleeve. With stock sleeves +0.040" is your limit. Then you need Pistons. Save sleeves for when it's needed. Offsetting adds very little to the cost of a rebore it takes me seconds extra to adjust the machine for offsetting. To Rebore to 72.5mm would be £100. That's much cheaper than a sleeve job.

Ac

Edited by ACDodd, 29 October 2014 - 07:24 PM.

[Cooperman]

Personally I don't like greatly over-bored engines. I recently put a worn 1330 back to 1275 with sleeves & a set of 21253 pistons and the job was not expensive. It restored the engine to original and re-lifed it. Each to his own, but unless for competition I really can't see the advantage of engines bigger that 1330.