Hi guys,
I now have disc brakes WOO HOO. This opens my engine options up as well WOO HOO.
I have an 1100 but.. its knackered and needs a total rebuild, my box needs rebuilding and can be bolted to anything anyway. anyway back on point, should I just work the 1100 of ditch it and get a 1275? I need to pretty much buy new everything anyway and wether its for a 1100 or 1275 wont make much difference anyways, the only cost I see is the short motor
What do you guys recon?

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If you go for a 1275 short motor, there are various bits that are different & don't transfer from the 1100, so watch it. They will add to your cost.
Some of these bits-
cylinder head
pushrods (1275 are longer)
oil pump (shaft length and maybe drive type)
primary gear (bigger bush in front)
radiator top bracket
top engine steady bracket onto head (if used)

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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.

yeah I thought there was a bit more difference. I ment to say bare motor, as in no intake, exhaust, gearbox. Most of the bolt on stuff that I would have upgraded on the 1100 would fit an 1275 anyway.

The other option I was looking at was building a mild but reliable 1100 getting it rego'd (through regency etc) then put a supercharger on it. But the way I see it a supercharger Kit would cost about the same as a rebuildable 1275 any way.
The only thing to consider would be the final power output. Anyone have an idea what the power figures are for a worked 1275 and a worked 1100 with a hairdryer?. I spose if i supercharge an 1100 I got no where to go afterwards. What kinda power would I expect from a blown 1275?.....mmm

Cheers

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1275 in the end is the way to go. No substitute for cc's as Vizard says.

Having said that, I've driven 3 different mini's in my life (2 regularly), never driven a small bore. But I think the 1275 is just enough power to keep up in traffic.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

jeez, 1275 just enough to keep up with traffic. Heaven forbid I should try and beat anyone
Thats no big deal really. I have another car that is plenty fast.
slinkey ur blowing yours arnt ya? what do you expect from it ?

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I started it with blower for the first time today, had a bad induction leak so I had to disassembly it a bit, and haven't put it back together yet.

Ok I got 50 hp at the wheels with twin 1 1/4s, then i put a Nissan dizzy on and the car gained a lot more top end so say ~55hp (ATW, my guess) 7psi (more like 8 though) add about 45-50% more powerish. My guess is somewhere in the 70s at the wheel, im hoping to crack into the 80s but I don't want to say much till I have the proof.

Either way, a fair bit more than a stock 1275.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

It will cost you around about the same price to do a 1100 as it would to do a 1275, (apart from the expense of buying the 1275 parts in the first place).

Pistons and rings - relatively same price
Bearings - relatively same price
Cam grind - same price
Gaskets - mostly same gaskets
headwork - pretty much same price
Block boring and honing - pretty much same price

you also get a free 20-30hp more, so why not??

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Lillee - 1969 Morris Mini K

yep always go a bigblock if you can afford it..
of course they do use more fuel tho...

yeah thats what I was thinking. Then If i get bored I will put a hairdryer on it.

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Hey slinkey - you only got 50bhp atw? I know dyno's vary but sxc_clae on here got 45.9bhp atw with a mild worked 1100... I hope you get the extra horses you're expecting with the blower

And I think you'll only use more fuel with the big bore if you're constantly planting your right foot into the carpet... the stock 998 I'm running atm uses more fuel than the worked 1300 I was running (which died ) which I'm assuming is because the 1300 didn't have to 'try' as hard

willy's 998 got 47 hp at the same dyno day... the most powerful smallblock got 50...
my 1310 got 55.7 and i was damn sick of how crap it ran

obvious differences in torque, but you can lose or gain a LOT depending on how well its running..

a well setup powerful smallblock is preferable to a tired smokey crapped out bigblock..

My engine is not tired out....

It was about 5000k's old at the dyno day.

Dodgy dizzy. (crappy 850, totally the wrong curve!, and warn out which makes it worse)

Interestingly, When just about to take appart car for S/C mod I checked some things, my throttles (twin SUs) did not fully open at pedal rammed into the carpet, so I guess that would bring the pwoer down, plus they were 998 Cooper Carbies.

Ok if you go by some sources then 50.3 bhp at wheels makes 50.3 KW at the engine. Much more than 30% loss if you go by that. But that makes a bit over 80hp at the crank so I guess that system is a bit wrong.

My engine was a stock Cooper S engine .060+ but with 1275 pistons not S pistons, giving a stock 1275 compression.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T