I am definitely not a mechanic but I do drive a 1380.

I have had no problems with my engine since it was built at Northern Mini Parts several years ago. The engine was built and installed in my mini before it was taken off the road for two years (had a face lift). Then went back into my mini (no mods done just painted and shinied) and is still there.

I have made several trips to S.A. from Vic and attended all Vic Mini Club events and used to drive the mini daily till the recent make over with no probs at all.

Never broken down.

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mutant mini 1380cc '73 UK imp-Chroma Lusion-leather interior-8 x 300W Diamond Audio Dual Voice Coil 8" subs, Phoenix Gold 4 chnl amp, Pioneer 7550 DVD, 2x Phoenix Gold A1.800d MonoBlock Amp, Focal Utopia splits, 14" chrome rims 195/40/14 tyres

I can still dream of a reliable 1380 all of my little own??

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You're only supposed to blow WHAT off?

Hotbrick,
No there are no problems with 1380s breaking down. As reliable as a 1275..
It's a good mod. Only problem is when it's worn out, it's hard to bore it again.. as 74mm piston supplies have mostly disappeared.

BUT.. if you are going to turbo it with lotsa boost, remember the cylinder walls of a 1380 are pretty thin. Some people reckon too thin for turbo... they prefer to keep to +.040 bore, and then stroke it, by offset grinding a big journal crank and using S rods. Gives U around 1400cc..

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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.

Do different 1275's (from different eras) have different wall sizes?
If so.. how much different? which is the one with bigger walls for the safest bore?
Thanks.

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regards,
MiK

No, there's stuff-all difference in wall thickness between the 1275s, except that Cooper S blocks are supposed to be a bit thinner. But they do bore OK to 1380 most of the time.

The Oz Morris 1100S blocks are as good as any- back in the old days Lynx Engineering used to bore them to 1426..

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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.

that is what my 1380 is a 1100 s block
makka

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Anonymous moderation means the agro that is built up towards the mods isn't aimed at an individual (fewer "Makk" attacks). Less stress for mods means less moderator "retirements".

hello,
iv been told by 5 people that have all done it 3 or 4 times,that there is a risk that you can split water jackets going to 1380 and the boars can turn to crap from the cast when ya go out to 1380,so the block might be dead B4 i eaven get it running ,have also been tolf that the boars need to be offset in order to goto 1380,im thinking this is gunna cost more but ya get that.
in plans it will be a 1380 with a 45mm weber on longman manifold with a 286 cam and some of them 3-1 extractors,and that is all im going to doto her untill i finish off the rest of the car,can some1 give me a guess at how much BHP it will make?
thanks alot

It is good practice to offset the bores when going to 1380. This is because a stock 1275 has less metal between cylinders 2 & 3 than the others. If you bore straight to 1380 it's pretty thin there and it means you won't be able to bore to 1400 later, if needed.

crap does happen sometimes, but hey if you're worried, just bore it to 1330...

We dynoed Baracade's 1380 on Graham Russell's ENGINE dyno after I built it last Xmas. It made 110HP and 106 lb/ft torque with a 45DCOE Weber, 286 cam, offset bushed `S' rockers and an LCB....
It's an S block, bored to 1380..

<edit> It's a road car- the inlet manifold and head could stand more porting work. Like mine has...

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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.

Just like Doc Mini said. The bores of No's 2 and 3 cylinder are very close together. Boring them out to 1380 leaves the wall VERY thin. Offset boring takes more metal out of the other side keeping the wall to a more respectable thickness.

The only thing I was thinking about is, IS a different crankshaft needed since the bores are off centre now, from standard?

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"He's always been a dickhead, He always is a dickhead, He will always be a dickhead. So stop complaining when he acts like one."

No. It's bored only slightly off centre, (.015" I think) there's plenty of space between the rod little end and piston bosses.

BTW, Graham Russell now has some 73.0mm (1360cc) Hypatec pistons in stock. Very nice... dunno the price though!

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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.