I am planning on rebuilding a 1098 motor for my clubby, I have read all the threads around 1275 vs 1100 etc etc and although a 1275 will ultimately give more power, I still want to do something with a small bore, just cause I can. I have been reading with interest the 68mm project that GR has been doing and I also really like the idea of going with an SC12 supercharged motor and thought I would throw it open for comments from the wise and wacky on here. Think of it kind of like an engine designed by committee !!!

The car is used mostly for weekend drives, club meets and the odd drive to work, it wont do a massive amount of freeway driving. The rest of the time I use the motorbike as I am not a big fan of sitting in traffic. So I am looking for something relatively fast and very fun, running costs like fuel etc are not really a concern for me. I would like something that is relatively reliable and doesn't need pulling apart every few months.

Starting with a standard 1098 engine what would you do, what bore size, cam type, extractors, carb set up, supercharger, etc etc etc

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1972 Leyland Mini Clubman
2000 Honda CBR929RR

If I didn't already have a 1360 in mine, I'd bore the 1098 to 68mm and just follow GR's build.
But I'm old school, I distrust turbos or huffers on an A series. I've seen many go BANG over the years.

However, if I was going to S/C it, these days I'd use a Sprintex blower. The SC12 one is getting old and many parts are just NLA now.

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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.

There are just so many options these days. I was at World Time Attack in Sydney in October and a company stand there was selling new turbos. The smallest one was good for a 1 litre motor and the unit was less than $600! It was tiny, like a grapefruit size and good for about 100kw. Apparently it was a direct replacement for one of the small VW engine ones.

So you have old Roots blowers which are cheap and kits from Ben are readily available so no fitment stress. Then you have Sprintex screw type blowers which are vastly more efficient but $$$ and you need to make your own kit. Then ther are second hand turbos and even the new ones I mentioned above. If you are rolling in cash you can even go a centrifugal blower for excellent efficiency but non linear boost but these retail for over $2500. They do come in very small sizes though.

Next you have the hard part. How to fuel it... You can go suck through carby or efi. You can go blow through carby but not really efi if you want to avoid charge robbing or you can swap the head to a cross flow and do port injection (like me).

Your roots blowers are the least efficient and will heat the charge much more. Ideally you would have an inter cooler but that isn't feasible if you have a suck through.

If you keep the carby you may want to swap the dizzy for one with boost retard but that isn't really required for a blower than can develop instant boost at all revs. Much more useful for a turbo so you can have some more advance during the lag period.

Anything that has a large volume after the throttle butterfly and before the blower will get very cold at low throttle. It's physics, not the carby type that causes it. So the best thing to do is put the throttle as close to the blower inlet as possible. The inlet temp isn't an issue of you inject fuel in a different location to the butterfly.

We need more people trying new stuff with their minis. Matt Read has built all sorts of stuff and there are some cool builds around but not written up on the net. I hope you get inspired and do something unique!

M

Thanks Doc the results GR is getting are very cool and this does seem like the more conventional / tested way to go.
Thanks Mokesta now I have even more stuff to think about. Time to go away and do some reading me thinks, hmmm Turbo

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1972 Leyland Mini Clubman
2000 Honda CBR929RR

I'm also interested in this however I would plan to build something along the lines of the 68mm.

Are there any good bang for back enhancements that can be made to the 1098 before going the whole hog?
I may look into these as an option before I pull the motor out.

Cheers,

The secret to getting good HP and torque from any A series is the camshaft.
If your 1098 is in excellent condition, the cam (and NEW reground lifters) can be changed in the car.
Need to snip one of the radiator slats in the LF guard (and weld it back) but it's way easier than pulling the engine to do it.
Of course if the engine is high mileage, doing a cam change is a waste of time. Pull it out and rebuild it properly too.

Add ons to your existing 1098:
Twin HS2 carbs or a single HS4, and a freeflow or LCB exhaust manifold will add 5HP or more.

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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.

A thread like this will always bring up more questions and options than answers. Like Mokesta pointed out just the vast options with forced induction.
You already know you want to do a 1098 which is the first step of many, 2nd question do you want to do a cross flow head or stick with a 5 port iron head
Once we know these basic things we can then look at the other parts, fuelling, induction etc etc.

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Respect mine and I'll respect yours.

I tend to agree with you here Doc, BUT, I'm a big fan of the hair drier on the exhaust! The power is not there all the time, only when you want it. Unlike a supercharger, when it starts to produce boost, it is always there.

An engine that has been designed for either a supercharger or a turbo has all the parts, plumbing, emission hoses, ignition curve / map, fueling supply and of course the essential, fuel metering / map! If any of the standard required equipment to run either setup is left off, a recipe for disaster is inevitable. The most common problem I think is ignition curve / map and fueling requirements for the extra boost most people want.

The problem I see when people add these items to a normally aspirated motor, is they get greedy! They want more and more power and don't stick to the original boost they built / designed the motor for. The idea of developing a new engine induction system is to take your time and do things in small steps instead of leaps and bounds. For example, bolting a turbo setup straight onto a N/A motor and taking it for test drive with "Let's see how much boost this makes!" comment as your driving out the driveway! I can see the end result now.....

But to answer simo's original question.....If you do your homework correctly, a N/A small bore with todays engineering skills, will result in a power plant that will rival a lot of standardish 1275's. Bolt on either a turbo or supercharger, with the right cam, and I think you will be more than happy with the end result.

Cheers Shane

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If it's not a Cooper S, the mini was designed to be modified!

Thanks for the feedback guys this is all good stuff and is keeping me busy at work researching other websites and engine builds !!! Oops didn't say at work, only at lunch honest guv.

Kennomini with regards your question about iron or cross flow head, I haven't really decided yet. I already have a nice fairly stock 1100 and it runs nicely. I Have a spare 1100 motor in the shed and want to build something different but Like everyone I don't have endless cash. I would like to assemble the engine myself but recognise their are limits to my abilities so a major engineering project that is new and bespoke is probably a stretch too far.

Let's for the sake of the discussion assume I can spend up to $10k (pretty sure the wife doesn't read this), on parts, engineering and tuning and set up. What options are there to make a really interesting small bore pocket rocket ?

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1972 Leyland Mini Clubman
2000 Honda CBR929RR

I'd say if you have around 10 k's to chuck at the engine , you will end up with a pretty mean small bore engine .

Send gr your 10g and your engine and im sure you would get something pretty sweet in return.... pro bably some change too..

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The best part of fixing your mini is the test drive

Minis..

1976 van daily drive
1975 van
1968 deluxe in the shed
1967 deluxe high strung 1310
1959 austin healey sprite

Sorry to pull up an old thread, but what did you end up deciding with this?
I am currently thinking along the same lines of a 1098 ->68mm with a SC12. Would be great to hear of what you came to decide

@miniRock - I am still deciding !! Unfortunately since I started this thread we started a fairly big extension and renovation of our house and have moved out for 6 months. That means the garage is full of stuff we didn't want to move from the house and there is just enough room to get the mini out for a drive but no room for any engine work. The budget for the extension looks like it is going to blow out a bit and is probably going to eat into the engine fund for a little while. I figure this is a small sacrifice to pay for an otherwise happy wife, happy life. The car just needs the interior seats re-trimmed to finish it so that will be the next job which I will do before summer and then I am just going to drive it and enjoy it. The motor that is in there runs great so not in any rush to swap it over. I have been reading lots of other threads and sites about small bore tuning and still really like the idea of doing a turbo motor, but it may be a case of keep reading and researching for now and maybe start buying parts a bit at a time.

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1972 Leyland Mini Clubman
2000 Honda CBR929RR

Hey mokesta, what engine setup do you have? What size engine is your crossflow on and is it efi? Also is it supercharged or turbocharged aswell?
Curious as Ill be building my engine soon and I have a 1330cc engine and a 7port crossflow head for it.
Cheers ian.

If you had 10G to throw at a motor you could end up with a stink hot 1275 and bin the 1100.
You may be better off making your own decision first and then asking for guidance. Problem is we ALL get greedy, and its usually a wasteful and expensive mistake to correct. Its like pitching up with your cheeseburger and your mate rocks round with a quarter pounder. Not loving the happy meal anymore are you.

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1970 Cooper S ex-Bathurst & ATCC
1964 Austin Cooper S ex-Group C race car
1967 Morris Cooper S ex-Group B
1962 Mini Speed sports sedan
1968-71 ex-Peter Manton Shell car