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Bore /engine size
https://www.ausmini.com/forums/viewtopic.php?f=2&t=77941		 Page 1 of 2
Author:  66S [ Tue Aug 07, 2012 11:53 am ]
Post subject:  Bore /engine size
Hi guys,
I am sure we discussed oversize 1275 bores a while ago and what the various oversizes meant in cc's but I can't find it using the search function. Does anyone remember it?

I have a block that is .060" (1.50 mm) oversize and I work it out to be a 1380 ??

I have another that is .80" (74.168mm) oversize.

Regards
Al
Author:  justminis [ Tue Aug 07, 2012 12:17 pm ]
Post subject: 
Al
+0.060" is 1330cc. +0.090" is 1360cc (73.00mm bore). +0.115" is 1380cc (73.50mm bore).

Your +0.080" (74.168mm) figures don't add up. Sure you measured it right?

Steve
Author:  66S [ Tue Aug 07, 2012 12:35 pm ]
Post subject: 
Hi Steve,
I was struggling with it too. I didn't measure that one so it is possible the measuring is screwed up. Maybe I need to check it I reckon. Thanks for your response.

Al
Author:  TheMiniMan [ Tue Aug 07, 2012 2:09 pm ]
Post subject: 
.020 is 1293
.030 is 1303
.040 is 1310
.060 is 1330
.094 (73mm) is 1362... add an 84mm stroker crank you have 1412
73.5mm is 1380
74mm is 1399
74.7mm is 1426,,, add a 84mm stroker crank & you have 1485

add an 86mm stroker crank to that last one & you have 1510

add a 91mm stroke crank to that last one & you have 1600cc

roughly ,,, but this is what they`re all commonly called.
Author:  66S [ Tue Aug 07, 2012 2:27 pm ]
Post subject: 
Great stuff thanks Miniman !!

Regards
Al
Author:  Irish Yobbo [ Tue Aug 07, 2012 3:40 pm ]
Post subject: 
There's a pretty good guide right here: http://www.theminiforum.co.uk/index.php ... -my-engine
Author:  mini_mad_matt [ Tue Aug 07, 2012 6:25 pm ]
Post subject: 
I don't suppose you have confused yourself with radius and diameter when going from measuring to calculating? Or have your formula wrong?

Just thinking that 60thou is practically half of 114thou which is 1380.
Author:  Kennomini [ Tue Aug 07, 2012 8:38 pm ]
Post subject: 
Good list Matt :D .
Author:  mmiller6512 [ Tue Aug 07, 2012 8:45 pm ]
Post subject: 
Wow that 1600cc sounds like FUN.
Author:  drmini in aust [ Tue Aug 07, 2012 8:54 pm ]
Post subject: 
mmiller6512 wrote:
Wow that 1600cc sounds like FUN.

Read Vizard's yellow book (end of `big engines' chapter)- he reckons the 1600 he built was rough as guts vibe wise, and it had way too much internal friction because of the LONG stroke.
Except for low down torque, he says a 1480 would beat it for most purposes.


/waits for TheMiniMan to chime in... :P
Image
Author:  CARTER_GT [ Tue Aug 07, 2012 10:56 pm ]
Post subject: 
drmini in aust wrote:
mmiller6512 wrote:
Wow that 1600cc sounds like FUN.

Read Vizard's yellow book (end of `big engines' chapter)- he reckons the 1600 he built was rough as guts vibe wise, and it had way too much internal friction because of the LONG stroke.
Except for low down torque, he says a 1480 would beat it for most purposes.


/waits for TheMiniMan to chime in... :P
Image


Because of such long stroke would be an awesome highway cruiser would it not!? Someone tell me how wrong I am
Author:  66S [ Wed Aug 08, 2012 1:29 pm ]
Post subject: 
Thanks guys, that is all very helpful. The problem with the questionable bore size above turned out to be a faulty imperial to metric conversion, it's actually 1380 cc.

Thanks again
Al
Author:  TheMiniMan [ Wed Aug 08, 2012 3:04 pm ]
Post subject: 
CARTER_GT wrote:
drmini in aust wrote:
mmiller6512 wrote:
Wow that 1600cc sounds like FUN.

Read Vizard's yellow book (end of `big engines' chapter)- he reckons the 1600 he built was rough as guts vibe wise, and it had way too much internal friction because of the LONG stroke.
Except for low down torque, he says a 1480 would beat it for most purposes.


/waits for TheMiniMan to chime in... :P
Image


Because of such long stroke would be an awesome highway cruiser would it not!? Someone tell me how wrong I am


Well,,, the 1600cc donks are VERY torquey & i mean """VERY"""!!!! & yep, i love em to death... They`re just awesome in that respect ,,, but yes they fall a bit short in other areas & in my opinion it`s not worth doing when coupling up to an old A-series head.

even Stews 1600 with Arden alloy crossflow head ,,, well it`s wicked & awesome & everything you`d want from a big race donk,,, but just doesn`t "Sing" like a 1415 or a 1360... we hold it up at 7500,,, i don`t want it going any higher,,, but i highly doubt that it will go much past there anyways... & no, we`re not going to try & see either :-)

When you have a 1415cc stroker singing at 9000rpms,,, well ... :-)

physics tells us that a short stroke "should" sing even better,,, but i know how well 1415cc strokers spin & sing so in my books, in my experience, you can make a stroker sing,,, just don`t go past 1415cc & you`ll be fine :-)

My 1510 donk only went to 7800 ...( & it does that all day every day mind you) but still i couldn`t make it go past the 8000rpms mark--> except when Peter Osborne ran it at Mt Cotton Hillclimb & after hitting about 6500 in third,,,, thinking he may not make the next corner, he slipped it straight back into first--> go do your sums boys & girls & then tell me what rev it was """Made""" to do :-)

But,,, in saying that,,, these Bimmer-twinkys can sing i can tell you,,, so it`s more to do with the ability to breath,,, """coupled with""" the harmonics-smooth-ness that makes them work sooooo well

if you can get a mini engine to breath really well,,,, make it spin nice & smooth,,, & rev really high,,, as well have Heaps of grunt down low,,, then you`re on an absolute winner

So ,,, yes a Turbocharged 1415cc 16v Twinky will (i reckon) be the ultimate.

sorry, getting off topic (again) back to the capacity chat again.
Author:  Paddy [ Wed Aug 08, 2012 5:17 pm ]
Post subject: 
Quote:
So ,,, yes a Turbocharged 1415cc 16v Twinky will (i reckon) be the ultimate.

sorry, getting off topic (again) back to the capacity chat again.


Do u have some more detailed specs about this ultimate engine, I'm currently trying to decide what to put in my mini and this sounds very good
Thanks
Paddy
Author:  TheMiniMan [ Wed Aug 08, 2012 8:35 pm ]
Post subject: 
yes, we off-set bore out a 1275 block to 73mm (1360cc) then we off-set grind a large journal 1275 crankshaft, (stroking) lengthening it`s stroke to 84mm , making the engine a 1412cc (i call em 1415s just rounding up a tad)

we then use small journal ("S" type) con-rods & narrow them 14thou per side (i just make it 15thou per side actually) & then they fit the large journal crank width nicely

with the top of the block modified to suit the BMW twin-cam cyl head... & the twin-cam cyl head modified slightly to fit ,,, stuff some pistons in there that suit the application (depending on forced indution or N/A) & add some other bits & bobs & fiddle with a few others,,,, you can then bolt it all together with one of my Twinky-Conversion-kits... & you`ll have a 1415cc Turbocharged (or N/A) Twin-Cam, injected, rocket-ship mini engine that is impressively smooth, quiet & extremely powerful.

i`d definitely add a limited slip diff, & a central oil pick-up & make sure you have a heavy-duty clutch & a really well built gearbox & all will (should) be well if you keep boost under 15lbs.

if you like to go faster than that???,,,welll.... then you can just add more boost :-) :-) :-)

BUT!!! ---> be warned--> 20lbs boost with one of these things is ludicrously fast!!!
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