hey guys,

just wondering the biggest a 1275 can be taken with a supercharger and still be a reliable driver for road?

cheers

Bill

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http://www.ausmini.com/forums/viewtopic.php?t=71255

Theres no reason why you shouldnt be able to bore to at least 1380cc and then stroke the crank to get up to the high 1400s, the capacity isnt your problem, its making sure the engine is built properly and doesnt have too much compression.

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ok and will the compression be to high when im in the 14's for a charger?

regards

Bill

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http://www.ausmini.com/forums/viewtopic.php?t=71255

The compression will be what you make it, not enough & you can machine pistins & block, too much you can machine pistons & head. I would go for around 10:1 before the boost, you want it to go well before it starts too boost. Check out the Turbo mini forum and see what they have too say.

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strokes around 92mm have been squeezed into the A series, along with bores of 74.7 making approx 1600cc, I seem to remember Osselli did some 1608cc motors back in the day...

the biggest bore I would go for is 73.5mm also this is the largest bore you can get pistons with big dishes in (up to 18cc) it is probably going to get tricky getting the CR down above 73.5mm, I should add that I personally run a 1380 turbo 7 port as my daily drive.

heads can be taken out to pretty big chamber sizes, 28cc is common, 34-35cc is possible with selected castings,

stroke wise i'd imagine the crank is getting a bit whippy up rear 90mm, but i'd imagine 84-86mm could be good considering turbo'd engines don't need to spin too high...

if your really serious about a long stroke the block can be bored to take ford crossflow main bearings (2 1/8"), and a billet crank cut to suit, the details are in the big yellow vizard book.

I have built a number of "stroked" A series engines for Minis using Mazda Pistons and a 1505 stroked and nitrided crank. These pistons have a shorter deck height than the original 1275 Pistons and the compression comes to around 10 depending on the head chamber size. These pistons come in 73 - 73.5 and 74mm and they are more like a flat top with a slightly raised peak to the middle but they come to about 2 mm lower than the top of the block at TDC. This also depends on the stroke length. I have always used 84mm stroke Cranks. Pistons will need gudgeon pin hole honed to suit Cooper S pin. They are a very reliable piston. My red Convertible is running one of these engines with 73 mm bore and 84mm stroke.

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Vizard said yeah you can build a 1598 and squeeze a 91mm crank in, but also says it's pretty pointless for HP production. Too much added friction with the BIG stroke.
He reckons stop at 86mm or so stroke.

I'm running a 1412 with 73mm bore and 84.33mm stroke, only done about 100 miles since dyno run-in, but it sure feels torquey.

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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.

1620cc is available if you wanted,,,, but it`s a bit "If-y" in a number of departments

My dad sorted something around a 1700cc "Thing' for a speedway fella up north,,, not exactly sure of the actual capacity cause i was just a little kid back then,,, but around 1700cc,,, offset bored, then sleeved then offset bored again etc,,, add BIG stroke crank (welded up & re-machined)) & all the associated oil plumbing & clearance problems etc etc etc

I never went for a fang in it but dad said it was "THE" torque monster

& yes , as the good doc says,,, the HP on Massive mini engines "Usually" isn`t that fabulous for the sake of all the pumping losses & frictional losses & all the other associated losses,,, BUT THE TORQUE YEE-HAA !!!!!!!!!!!

Stewys Sports sedan is 1600 (1591cc to be precise) & it is also a MASSIVE TORQUE MONSTER,,, still revs quite hard,,, but short shift it & "WHOA""....---> hang on tight

Not sure many people in the world have had the opportunity to go for a drive in a mini engine this big but i can assure you it really is fabulous to drive,,,, if you accidentally slip it into 6th gear when going for 4th,,,, well it doesn`t care,,, it doesn`t seem to worry or even notice it & if you can fathom that sort of torque then you may have some sort of idea,,, but until you drive something this size,,, well you just don`t have a clue

My roady is 1510cc & is lovely & drivable,,, mlld cam & mild compression thing, keeps it very sedate & very calm,,, leave it in top gear & do whatever you want with it,,, most people don`t even believe that it`s so big when i take them for a sedate, smooth calm comfortable drive down to the shops,,, but on the way back i give it some & then they go--> FFFFAAARRRKKKK!!!!,,, ... click it back a couple of gears & rev it to 7800 every gear (inc top gear) with the 3.2 F/D ratio,,, it`s happy either way You can all do the sums to work out what a 3.2 diff & 7800rpms gives top speed

BUT!!!!!!!!!!!!!!!!!!! I`m working on this project,,, it`s a bit of a secret at the moment so don`t tell anyone,,, "IF" it works then we are talking (up-to) 1750ccs-ish & multi-valve,,, & i mean "MULTI"

The Bimmer Twinky had to be done, but this thing is (or rather "may be") on a whole `nother level again Expensive tho ... don`t think i`ll be making "Kits" for it like i have the Bimmer... Just simply "WAY-TOO" much for the average Joe-Jane Doe to comprehend , let-alone fork out the quantity of money needed to complete it

But still... the average Joe-Jane Doe is "Usually" quite happy with a 1380 or 1415 or even the odd 1430-1450 etc,,, nothing wrong with them as road engines if the cam & comp ratio is kept fairly realistic for pump fuel,,, dam good Roadys in my books

My suggestion to everyone who is after a VERY RELIABLE BIG mini engine for road use,,, is 1360cc,,, & add a stroker crank if you want that bit more,,, those 2 design engines are just fabulous , un-breako,,, wonderfull power units,,, just can`t go past them in the "Bang-for-buck" ratio really (IMO)

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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 would go a 1293 or 1310 with a supercharger set up and a good head.

you will easy see over a 100hp look on the turbo mini forum

see what them boys are getting.

do one of matts kits get 120 ish from a 8 twinky.

problem seems to be gearbox, matt seems to smash alot of power through them & no problems.

talk to him or gr about a strong box.

gearboxes are not really a problem until you get close to the 140-180HP mark,,, if they`re well built that is,,,

it`s more about the Torque that mashes them tho

above 140- 180hp it`s a matter of ...well... i think you might already know the results

I`ve seen some turbo engines spread the cases & break main-shafts

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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.

221kph, or 137mph

hey Matt - don't believe it until I see it on a video

1360 for the road, 1460 for the track!

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Slide
1965 Mini Van (1360)
1970 Mk2 Cooper S (1310)
1978 Rover SD1 V8 (4.6)
1996 Land Rover Discovery V8 (4.0)

I like this topic! But it needs pics! SO, this is my block at 74.7mm (1426cc ish) Just to show how awesome the block walls are! - So thanks, im going to get into it now and get the damm thing together!

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