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engine options
https://www.ausmini.com/forums/viewtopic.php?f=5&t=61351		 Page 1 of 2
Author:  mushroom [ Fri Feb 26, 2010 11:40 am ]
Post subject:  engine options
i am about to start to build an engine for my clubbie and i have a couple of options.
1- 998 block with a 1098 crank and 60 thou pistons, mild cam, 1.5 rockers, bigger valves and a supercharger.
2- 1275 with flat tops, mild cam and head work
3- same as option 1 but with 998 crank.
I have heard that 1098 cranks are weak, is this true? Can they be strenthened i am leaning towards 1 and 3 and i figured that a 1098 +60thou would be around 1200 and rev higher than a 1275. Any advice, constructive critasism or opinions from people who own or have driven a similar setup would be appreciated, cheers
Author:  mini is my ride [ Fri Feb 26, 2010 11:53 am ]
Post subject: 
Hi

I looked at what you are looking at just recently

I took many things into thought

1. 1275's can rev much higher
for example I know that a 1098 done up (as far as I was aware)
cant rev past 6000 revs if that, thats in normal form

2. The amount of work that you do to a 1098 can be done to a 1275
and get somewhat better results

3. some people believe that 1275's are unreliable but it depends on what
you do to it

4. A 998 block with a 1098 crank is better than a 998 with a 998 crank

These are my views I mean I have a 1098 block which I was going to
work on but than got a 1275 which I hope in many years time to fit a
supercharger

Also fitting a better flowing head on any of the A series motor's will
get you good results in Vizard's book he talks about the options
you have when it comes to A series motor's
Author:  mushroom [ Fri Feb 26, 2010 12:10 pm ]
Post subject: 
cheers, the main reason i am leaning towards a small block is i have 2 998 complete motors and a 1098 motor minus g/box and i only have 1 1275 bare block with crank caps, 2 cranks and a set of flattops.
Author:  mini is my ride [ Fri Feb 26, 2010 12:38 pm ]
Post subject: 
The choice is yours I understand
I have three complete 1098 motors
a running 998
and I went and brought a 1275
:roll:

so yeah

it depends on the cost too like for you it might be alot cheaper
and easier to do a 998 and if you break it it don't matter
as they are not that popular and you can pick a cheap one up
Author:  drmini in aust [ Fri Feb 26, 2010 1:44 pm ]
Post subject: 
1098s make a fine torquey road motor, even well modified.
Just keep revs below 7000max and 6500 continuous. Yeah they will go to 8000+ but not for long, I found this out the hard way.

998s rev better, but have to- to get anywhere. Compared to a stock 1098 they are behind the 8 ball- 10HP down. :lol:
But a 998 bored out +.100" is nearly 1098 anyway. Good power and torque when modded, and still near unbreakable.... :P

I like 1275s , but if you rev them hard you can break them, like a 1098.
Keep them below 7500, or 7000 if you want it to last.
Author:  blue_deluxe [ Fri Feb 26, 2010 2:19 pm ]
Post subject: 
What would a 998 rev to?
Im thinking of building a super high revving bimmer twinky on a 998.
Would 10 000 rpm be too far?
Or are the dollars to do it way to big.
Id run a 4.2 final drive and it could have some top speed if i could put up with noise.
Author:  drmini in aust [ Fri Feb 26, 2010 2:26 pm ]
Post subject: 
998 bottom end won't stand 10,000. 9,000 maybe, but not for long.
A 970 S might see 10,000(for a bit), but they are rocking horse droppings out here.

At over 7500rpm continuous, the wear rates in the A series engine (and probability of a big BANG) go up astronomically.
So waste of time in a road car.
Author:  blue_deluxe [ Fri Feb 26, 2010 2:43 pm ]
Post subject: 
I see, oh well, just have to build a 5 bearing crank and block together, right after i win the lottery...
Author:  blue_deluxe [ Fri Feb 26, 2010 2:46 pm ]
Post subject: 
I see, oh well, just have to build a 5 bearing crank and block together, right after i win the lottery
Author:  madmorrie [ Fri Feb 26, 2010 7:00 pm ]
Post subject: 
I went the whole hog on an 1098 (well it was 1150 I think). Did pretty much everything in the vizard book. It sounded awesome and went OK too, but in my opinion if you are going to go to all the trouble, use the 1275. If I did it again I'd definitely go that way. The cost to rebuild is gonna be much the same, and the result should be better for the same effort.

Madmorrie
Author:  TheMiniMan [ Sat Feb 27, 2010 12:05 am ]
Post subject: 
BMW motor-bike cyl head, twin caM , 16V, FUEL INJECTED , Turbo charged, 25ps boost 1360cc , rocket ship donk is the only way to go

:-)

seriously

Yeah!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Author:  mini is my ride [ Sat Feb 27, 2010 7:54 am ]
Post subject: 
sorry mini man but I might add it depends on
whether mushroom wants a kinda original mini
engine or your awesome engine

it depends on costs too :roll:

alright I am always one to spoil the fun :( sorry

what engine would you put your kit on mini man

998, 1098 or 1275?
Author:  mattsmadmini [ Sat Feb 27, 2010 9:41 am ]
Post subject: 
bigger is better... .but he has put it on a small bore.... which i reckon with 60hp would go like ducks guts! :twisted:
Author:  adamstuart [ Sat Feb 27, 2010 2:43 pm ]
Post subject: 
What kind of effort and cost would one have to put into a 1275 to get 1400cc out of it?

From basically scratch, unless something can be pillaged from my 998 (highly unlikely)
Author:  drmini in aust [ Sat Feb 27, 2010 3:07 pm ]
Post subject: 
adamstuart wrote:
What kind of effort and cost would one have to put into a 1275 to get 1400cc out of it?

From basically scratch, unless something can be pillaged from my 998 (highly unlikely)


You can just bore it to 1400 (74mm) but really, you are just giving block life away. I'd stick with 1330 or 1360.
$150 for a good bore and hone job, and ~$300 for pistons.
$140 for a crank regrind (or $240 if you want a big journal one stroked too). Add another $200 or so for 4x S rods if you stroke it.
$100 max for bearings and thrusts.
$60 for an oil pump.
$130 or so for a cam grind.
$100 for cam followers.

As for the head, it depends. New valves and springs and guides will cost about $250. Add head reco work, and porting if required.
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