Who has bored out a small bore block to 68mm.or bigger and how much metal was left in the cylinder walls.
Has anyone found any difference between small bore blocks IE early, late and morris 1100 ones.

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
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HI DAVID
There's plenty of metal to bore them that far, the biggest problem is the metal between 1and2 3and4 even after they have been offset,there's no difference in the blocks
Graham Russell

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"It's better to be not informed than ill-informed"

I've had 4 blocks bored to 68mm over the years (1x 997, and 3x 1098 Sprite).
The only problem was with one Sprite block than had a crack between two of the bores, we didn't see it when we started.
No fault of the boring. We just binned it and found another block.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Theres more meat between the bores in my 68mm small bore than my 74.7mm big bore!

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speed costs....how fast do you want to go...

oh yeah,,, you can say that again

we`ve done quite a few 68mm small bores,,, i have one here still with Imp pistons, but we`re doing a bigger one soon with re-sleave & motobike pistons (obviousl\y getting a Twinky Konversion tho)

Might even Turbo this one tho as the bike pistons are quite short

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

I am looking at a project where I am going to bore the block to suit the 74mm center dist of the honda head. I am looking at boring a small flange block out to 75mm and fitting a set of VW barrels machined down on OD and shrink fit into the block as a test run.
The vw bores for the 1200cc eng are 70mm , so I would bore out to std 1275 size. The vw pistons look like they would be a better match for a 3" stroke than the bike pistons. Evdently a lot of the VW after market pistons are forged and I doubt there would be a better grade of cast than what is used in the barrels.
What I am trying to work out is what the maximum size I can bore out to for the OD of the liners, just need enough wall left to support /seal the liners. Measuring the different blocks,early thin flange, thick flange[99h] and a morris 1100 block there seams to be a difference in the OD of the cylinder wall. I am not too sure if this is with all of them or just the few I have.
Time to crank up the boring attatchment and see what happens

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com