19 replies to this topic

[Compdoc]

I thought about boring to 1330cc, (+ 0.060) to get another bite of the cherry to 1380cc in case of wear or damage. But I seem to recall that somewhere I read that you cannot offset bore from 1330cc.

Presumably, the gap between cylinders 2 + 3 are closer with the + 0.060 straight bore than they with a +0.120 offset bore. Anybody got any ideas?

[ACDodd]

You can offset if the original +0.060" bore is not too badly worn.

Ac

[carbon]

I thought about boring to 1330cc, (+ 0.060) to get another bite of the cherry to 1380cc in case of wear or damage. But I seem to recall that somewhere I read that you cannot offset bore from 1330cc.

Presumably, the gap between cylinders 2 + 3 are closer with the + 0.060 straight bore than they with a +0.120 offset bore. Anybody got any ideas?

What bore size is the block at the moment?

[minimans]

Off set bore to 1330 then it's already done for 1380?

[Northernpower]

If memory serves me right you're looking for a minimum of 3.8mm to 4mm between two and three cylinder walls.

[Cooperman]

It depends on what you intend for the future.

With most classic cars, and the Mini is no exception, you are best always going to the next size bore then, in the case of the A-series, after getting to +0.060" oversize, when a further re-bore is needed, have the block sleeved back to original standard size.

[Compdoc]

 

I thought about boring to 1330cc, (+ 0.060) to get another bite of the cherry to 1380cc in case of wear or damage. But I seem to recall that somewhere I read that you cannot offset bore from 1330cc.

Presumably, the gap between cylinders 2 + 3 are closer with the + 0.060 straight bore than they with a +0.120 offset bore. Anybody got any ideas?

What bore size is the block at the moment?

 

It's standard 1275cc but needs a bore so as I'm changing the head and the cam I thought 1330cc was a good compromise for a bit more torque whilst still giving me some future repair options.

 

Off set bore to 1330 then it's already done for 1380?

I must admit, I'd never thought of offset boring to 1330. If its possible it would seem to be the answer.

[Swift_General]

If the engine has a standard bore then I would just rebore +0.02" oversize. Likely to be cheaper, leaves more life in the block, and the difference in capacity is likely to be negligible in terms of output.

[carbon]

+1 for above, if it's on std bore at moment would go out to +20 thou only.

 

There are other options for getting very good torque out of a 1293 but keeping good road manners.

[Northernpower]

My decision would be based on how much use the vehicle is going to get, if its going to be a weekend warrior and not a daily driver I wouldn't be so concerned about engine life. If its going to be an only vehicle and get regular use then I'd only do the minimum overbore. I can't see the point in saving the engine for a re-bore after 10 years of occasional use. The OP presumably wants to enjoy it therefore I'd suggest taking the above into consideration. 

[Spider]

As it's at 0.060" now, if not already off-set bored from the start, you might struggle to go to 0.093" (for 1380). Personally, I wouldn't try it, but talk to your machine shop man.

 

Just to put it out there, also consider sleeving it, you'll end up with a much better and longer lasting bore as well as a block that is less likely to end up as scrap further down the track.

[Cooperman]

I think the OP is still at standard bore and is considering going initially to 1330 then to 1380.

 

My advice is to go up in 0-020 steps until 1330 is reached, then at he next re-bore to sleeve back to 1275.

 

Very little is gained by going bigger straight away, unless it is for racing when the bigger bore might reduce a lap time by a second or so.

 

A well and accurately built 1275 will be just as quick on the road as a 1380, will be more reliable and cost a damn sight less. No need for expensive offset boring either.

[Compdoc]

Thanks everyone for the interesting opinions. It's not going to be a daily driver so I have decided to stick with 1293cc. Hopefully, that may postpone the next rebore for another 35 years. Or perhaps swap the whole engine for an electric motor and solid state batteries!

[Northernpower]

Thanks everyone for the interesting opinions. It's not going to be a daily driver so I have decided to stick with 1293cc. Hopefully, that may postpone the next rebore for another 35 years. Or perhaps swap the whole engine for an electric motor and solid state batteries!

But the question would have to be, how much would you oversize the batteries by?

[ACDodd]

It is possible to offset bore from std to +0.060" I do it all the time.
Linering is possible now and after 73.5mm bores.

Its always better to leave a block in maximum material condition for strength purposes.

So the choice is yours.

Ac