11 replies to this topic

[Neilson]

I'm trying to decide what to do with the engine on my project. It has a 998 standard engine at the moment but I can't decide whether to get a 1275 lump and go all out or to try and get the most out of the original.

If I keep the 998, the planned spec is;

266 cam
Twin HS2s
worked head
Megajolt
Lightened fly etc

My question is if I rebore the block to say + 0.060" what is likely to be the power and torque gains?

Edited by Neilson, 12 March 2013 - 05:14 PM.

[mini*mad]

nippy yes
a 1275 with just the cam will be a darn sight faster!
i've got one for sale atm ;)

twin carbs are good but difficult to get set-up right

my gf has
1275, kent 266 cam, single carb with k&n airfilter, maniflow LCB and a facet fuel pump putting out 72bhp AT THE WHEELS
90 or so at the flywheel

Edited by mini*mad, 12 March 2013 - 04:47 PM.

[jonny f]

You can play around with getting the 998 up to the 1275's power but you will most likely spend just as much as it costs to get a 1275 in first place.

Buying a 1275 you know you've started at highest point A-series wise.

[mini*mad]

you can get 60 hp at the fly with those mods
basing it on a 12g940 head (1275 worked head)

Then your looking at;
£200 megajolt
£150 for rebore (MRA do it)
£100 12g940 head
£20 gaskets all round
£25 hi-cap oil pump
£25 hi-cap water pump
£40 2 core radiator
£250 for minispares 998 +60 pistons
£100 uprated clutch for the extra power
£150 lightened flywheel
£75 reground cam
£30 doublevalve springs
£90 for new bearings all round

£500(new/£150 second hand) twin carbs
£30x2 K&N/performance airfilter
£50 electric fuel pump
£150 1.5 roller rockers?

then probably going to want the crank reground and hardened - £50?
mapping the ignition takes roughly 2 hours at £60 p/h = £120
twin carbs are a pain in the arse to set-up right too so if you dont have a hand doing that probably the same again
as your there will end up doing silicone hoses & HT leads, paint the block make it look pretty
that all costs another £100+

and it will keep up with a standard/softly tuned 1275

is it for insurance reasons? some people do this to the early mk1 minis for the cooper s nostalgia and keep the engine number

[jakejakejake1]

An N/A 998 is never going to be an absolute 1275 killer, yes you can upgrade them to beat a standard 1275, but then it won't take much doing to the 1275 to make it faster again.
If you are you to the expense of fully doing over a 998, why not go turbo?
If you aim for that from the beginning it won't cost any/much more to prepare the engine than it would for N/A.
There is a thread on turbominis where a guy turbo'd his standard 998, with standard pistons, and a slightly worked standard head (to drop compression ratio a tad) and managed over 90hp out of it. All for a few hundred quid - cheaper than you could get a 1275 and get it to the same power.

[mini*mad]

yeah could go turbo
have to be confident enough to chop the bulkhead up and weld in a box
or silly money on a mirage manifold (who's website isnt up any more? :S)

saying that i've gone the 1293 turbo route, hence the 1275 up for sale
but i've built it up for around the 150hp mark ;)

[jakejakejake1]

There are (slightly) cheaper options than mirage (who are still making manifolds, despite the website being down), like matty over on turbominis who makes manifolds. But yes you are right the manifolds are the expensive bit, or a bulkhead box as you say, which means that an IVA test will be needed due to shell modifications.
But compared to the price of buying a working 1275 engine you could have your manifolds for the 998.

[mini*mad]

good point, would still have to do the cooling mods and clutch etc. on top
and insurers still run away hearing turbo conversion and i've got full NCB @ 23!

[Neilson]

Fair enough, I probably would be better buying a 1275.

But as the original question, what would people say the estimtaed power increase could be by over boring a 998?

[J_Durnan]

It depends what you want from it. I'm very happy with my 998, but I wouldn't particularly enjoy driving it all day every day.

Mine is probably a similar spec to what you're thinking about (has twin HS2s and the 266 cam, for example) and it puts out 44 horsepower at the wheels. That's more than a 1275 SPi.

It's not slow, if that's what's worrying you. I can keep up with my mate's MPi quite happily.

[J_Durnan]

To add to what I've said, boring the engine won't make a great deal of difference to the power output. In terms of increasing horsepower the biggest bang for buck would be a different cylinder head and cam.

My engine is bored +20 thou (1014cc) but it's all the other mods that have pushed the power up.

[minilee94]

You won't be faced with iva testing

And totally depends how deep your pocket is imo I think tuning up a 998 is a waste of time

If you don't want to spend serious money then get a 1275 cam it ,hiff44 carb ,polished and ported head bigger valves can buy the old cooper big valve heads off eBay and you can go overbore 1293 1310 1330 etc but depends how far you want to go or super charged system