ausmini
https://ausmini.com/forums/

new donk
https://ausmini.com/forums/viewtopic.php?f=5&t=12978		 Page 1 of 1
Author:  inazuma_x [ Tue Nov 08, 2005 8:47 pm ]
Post subject:  new donk
looking for a replacement for my 998...was thinking of getting a 1275 A+, boring it out to 1380 and getting a nice supercharger setup (SC12 maybe? :P)

i am thinking of just driving it as an NA, unmodified 1380 for a while...if possible...and then upgrading it gradually as funds become available...is this a bad idea?

how should i go about this? buy a reco'd 1275 A+ and get it rebored? or accumulate engine bits, get a used block and get it 1380'd? or get a 1275 thats rooted and have it reconditioned and bored at the same time? is 1380 the right amount to get it bored out to? should i go bigger? smaller? i want it to be an FI engine eventually (not straight away) and want it to last a fairly long time as well as being fairly reliable...
Author:  awdmoke [ Tue Nov 08, 2005 9:48 pm ]
Post subject: 
Seeing as you are not in a rush, just keep your eyes & ears open.
Bargains do appear from time to time :wink:

Most engines will need a rebuild anyway, and most will be 1310 or bigger by now.
Just go to the next size up in the motor you buy - 1380 is the last step, no more after that as it is new block time.

If you want to run it without a supercharger for some time, you will need to drop the compression ratio once you fit the SC. You should be able to take enough out of the combustion chambers in the head without having to pull the whole motor again.
Author:  drmini in aust [ Tue Nov 08, 2005 10:03 pm ]
Post subject: 
1380 is about as big as it's sane to go now, supplies of 1400 pistons have dried up. But if you're going to supercharge or turbo it, don't bore that far as the walls are too thin. 1310 or 1330 bore is more reliable for this. If you want more cubes than that, I'd stroke it.

BTW, 1275A+ blocks are not really the best- they tend to be porous and many were sleeved at the factory. Morris 1100S or Mini 1275LS ones are better for big bore jobs. :wink:
Author:  inazuma_x [ Tue Nov 08, 2005 10:43 pm ]
Post subject: 
drmini in aust wrote:
1380 is about as big as it's sane to go now, supplies of 1400 pistons have dried up. But if you're going to supercharge or turbo it, don't bore that far as the walls are too thin. 1310 or 1330 bore is more reliable for this. If you want more cubes than that, I'd stroke it.

BTW, 1275A+ blocks are not really the best- they tend to be porous and many were sleeved at the factory. Morris 1100S or Mini 1275LS ones are better for big bore jobs. :wink:


yeah might go the 1330 bore and get it stroked out to something HUGE...how big can you go given my requirements, before your pistons drop out the bottom of the cylinder? :P

are 1100S/1275LS blocks hard to find?
Author:  drmini in aust [ Wed Nov 09, 2005 5:44 am ]
Post subject: 
inazuma_x wrote:
yeah might go the 1330 bore and get it stroked out to something HUGE...how big can you go given my requirements, before your pistons drop out the bottom of the cylinder? :P

are 1100S/1275LS blocks hard to find?


While it's `possible' to get out to 90mm stroke with a special MEGA$$$ crank, most `strokers' here make do with a large journal 1275 crank, crankpins offset ground to take Cooper S rods (which have 1/8" smaller big end journals).
My spare 12G1505 crank finished up at 84.3mm stroke and the journals are now std/std. If you are prepared to use undersized bearings, a little more stroke is possible.

Not done the sums for a 1310 bore, but with a `1360' bore job (73mm) mine will be 1412cc. 8)
Author:  inazuma_x [ Wed Nov 09, 2005 8:04 am ]
Post subject: 
drmini in aust wrote:
inazuma_x wrote:
yeah might go the 1330 bore and get it stroked out to something HUGE...how big can you go given my requirements, before your pistons drop out the bottom of the cylinder? :P

are 1100S/1275LS blocks hard to find?


While it's `possible' to get out to 90mm stroke with a special MEGA$$$ crank, most `strokers' here make do with a large journal 1275 crank, crankpins offset ground to take Cooper S rods (which have 1/8" smaller big end journals).
My spare 12G1505 crank finished up at 84.3mm stroke and the journals are now std/std. If you are prepared to use undersized bearings, a little more stroke is possible.

Not done the sums for a 1310 bore, but with a `1360' bore job (73mm) mine will be 1412cc. 8)


cool :)

now...speaking in terms of reliability and eventual power output...i am aiming for ATLEAST 100kw atf (~100hp @ wheels) but would be quite happy with more :) forced induction is the only way to go...but i am also looking into a twincam head (either from KAD, or one of madmatt's bimmer head conversions)...what sort of stress will these things place on the engine we are planning here? will it be breaking every few weeks?
Author:  jbeenz [ Wed Nov 09, 2005 8:44 am ]
Post subject: 
while this is on the topic of how far to bore, what size do you go to when you press liners in, i thought it was 74mm, if so, could some of these "shagged" 1380 blocks be relined and brought back to standard? sure the overbore possabilities are a little limited second time arround, but theres nothing wrong with 1293 or 1310?
Author:  TheMiniMan [ Wed Nov 09, 2005 3:08 pm ]
Post subject: 
In the "good old days" the outer diameter size of the new sleaves were 73mm (or .095thou over) & therefore any bore bigger than that would not be able top be sleaved "UNLESS" special sleaves were made to suit in a larger diam.

all this is possible these days tho & there`s some pretty wacky (good) gear around now days, we had some special (Honda) sleaves made up to suit one engine we did & they had special flanges on top & special this & that & were of some "special" material etc etc etc ,,,lots of specials there hey? :-) But,,,very very costly ...& in my books just aint worth doin (YET)!!!!!!!!!!!!!!!! when good cond 2nd hand 1275 blocks become harder & harder to find, then that`ll be the time for "Mr Bulk Sleaving" to make some up. :-)

anyways,,,the thing to do would be as the good Doc says & keep it as small as you can (within reason) & the best that we`ve found over the years is the 1412cc combination,,,still small enough in the bore to keep bore flex at a minimum, yet way big enough for decent grunt to be produced with the aid of a stroker crank,,,may dad designed some pistons to suit this exact combination & they have prooven to be bullet proof over the last 20 odd + years.

The stroker cranks commonly used are then (again as the good Doc suggests) a large journal ground down offset to small journal size & then narrow some "S" rods to suit & Bob`s your Aunty :-)

we`ve been building those exact engines since 1969 for both road & race, easy-peasy

we`ve built many many an engine at bigger than 73.5mm bore in "offset" guise & some break through some don`t,,,not worth the muck around if you only have one block to play with,,,& yeah, i wouldn`t recomend the A+ blocks at all, YUK!!! but hey,,,you takes your chances some times,,,heck my own roady donks (2 off) went out to 74.7mm :-) YEAH!!!!! add the 86mm crank what do you have???yeah YUMMY!!! :-),,,but,,,not really suited for forced induction that well,,,

& Andrew,,,it`s not really a matter of just boring it really big & stroking it really long as there`s other issues,,,avaliability of the correct piston for one,,,the need to skim/machine down the dist drive shaft in some cases is another,,,piston deck heights , gudeon pin sizes & thicknesses & strengths & piston ring suitablility,,,etc etc etc

homework is needed to be done before you just make up your own engine size

we`re currently building a road going turbo charged, 1460cc (bored & stroked) suzuki pistoned engine for young Stew, he`s the one with the Arden crossflow , 6speed dog box, 1600cc powered sports sedan mini shown at the Qld Mini Muster show page in Mini world magazine recently & his new roady turbo engine has had to have the block deck shaved down dramtically to bring the comp ratio back up to reasonable point even with the forced induction, simply cause he got the low deck pistons cheap, go figure,,,:-) we all try to build a donk around what we want as an end result & he goes trying to build one cause he got some pistons & rings cheap, we had some homwork to do there i can tell you

It`s often best to go with a "Known Quantity" rather than trying to make something up from nothing with no experience ,,,& all i can say there is that we`ve allready done the homework on the 1412cc donks,,,we`ve allready done the R&D over the last 30 + years with piston design ...& they`ve been tested for all that time too,,,now that`s a dam good "Known Quantily" in my books

but then,,,i am a little bit biased towards those motors :-) if you havn`t noticed :-)


But ,,,all that said,,,there`s plenty of combos that work quite well,,,don`t have to do what i say, just do you homework first.

I just hate seeing/hearing of waste,,, waste is wasted goodness. :-)
Author:  inazuma_x [ Wed Nov 09, 2005 3:16 pm ]
Post subject: 
TheMiniMan wrote:
It`s often best to go with a "Known Quantity" rather than trying to make something up from nothing with no experience ,,,& all i can say there is that we`ve allready done the homework on the 1412cc donks,,,we`ve allready done the R&D over the last 30 + years with piston design ...& they`ve been tested for all that time too,,,now that`s a dam good "Known Quantily" in my books


i'll take one to go please! :)
Author:  TheMiniMan [ Wed Nov 09, 2005 3:29 pm ]
Post subject: 
You want fries with that???

:-)
Author:  inazuma_x [ Wed Nov 09, 2005 3:31 pm ]
Post subject: 
TheMiniMan wrote:
You want fries with that???

:-)


and a diet coke...deep fried :)
Author:  TheMiniMan [ Wed Nov 09, 2005 3:49 pm ]
Post subject: 
regular or upsized?
Author:  inazuma_x [ Wed Nov 09, 2005 5:02 pm ]
Post subject: 
TheMiniMan wrote:
regular or upsized?


what a silly question...do i look like a regular guy? upsized ofcourse ;)
Page 1 of 1 All times are UTC + 10 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/