Hi all,

Hoping to take delivery of a 998 soon. The roundie I am planning on it going in will need a resto but I was wanting to mod the 998... Other than blower or turbo what else can be done? Can the 998 be bored out? If so to what size? Ultimately the roundie will me a modified mini and far from original spec.

I have a nice 1275 in my cooper s bur want a modified mini as its brother.

Hence the next project.

But I was hoping to get some innovation from the ausmini mini lovers.

Cheers,

Zulu

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Zulu...

1967 mini Cooper S

Easiest and simplist

get an 1100 crank and a 12G295 head (mini cooper head) and chuck in it.

OR

you can bore it out and put imp pistons in it and bolt a 1275 head to it (this is what mini_rusty did)

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^ that.

A 998 and a 1098 can both be OB .100 a 295 head or well worked 202, RE83 or 13 plenty of up and go good for 50hp atw

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Here am I sitting in my tin can far above the Moon
Planet Earth is blue and there's nothing I can do...



“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

What about a 7 or 8 port alloy head...the biggest problem with the A series head is it's restrictive port design, an upgraded head will free up a whole heap of power. Both the 998 and 1098 can be bored out to .0100 or 0.120thou oversize, Graham Russell makes the big pistons or you can get .020 to .080thou from must mini suppliers.
You could also ditch the dizzy and go for a crank angle sensor and coil pack ignition system.

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Respect mine and I'll respect yours.

Most 7 or 8 port heads are designed for a 1275. If they flow much better than a 940 head does (surprise, some don't) they are probably too big for a 998 or 1098 roady.
If you are hellbent on running a 7 or 8 port A series head, I'd slide a 1275 under it first.

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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.

stuff making it an 1100.
I did a 998 with 040 rebuild, 30/70 cam, 1.75 inch su, minispares manilfold, extractors and sports exhaust, mild work on the head.
It was a screamer. Revs and it pulled like a school boy.
This thing lasted forever and copped a beating.

Doc can you tell me which 7 or 8 port head doesn't flow as well as a 940?

Sorry Ty,
I was thinking of the original Pearce 5 port, my keyboard fingers got carried away. I should have said alloy heads... not 7 and 8 port.

PM sent.

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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.

Is it worth it for 50bhp? Turbo it or buy a 1275 I'd say. Then your starting above where you'd be finishing with a small bore.

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Potato

What else do you want to do to it? Do you have a power figure in mind? Or an application? A large head will flow well but kill airspeed, not ideal for around town, same as a large cam. A turbo is not a bad route when the big N/A bill hits your wallet, and can be more efficient on fuel.

Fit a BMW twin cam, similar engine size flows much better and is crossflow to boot. Again, expensive. Boring it out will increase oil consumption (or so I am lead to believe, the imp pistoned minis supposedly did) and probably increase blow by, contaminating the oil your gearbox lives in.

Having an idea of what you want to achieve will encourage useful discussion rather than 100 different ideas with as many different applications.

All fair points. The last made me realise how specific I need to be... This won't be a daily driver. It will be weekender for fun and shows. Needs to be driveable for longer trips at high speeds. I want reliability and performance. But it needs to sound like car porn. I don't want to do a conversion as I like A series. My 1275 is great but was thinking more 1380. Perhaps the 998 is no good. Perhaps I need to sell all 3 that in getting and go for a 1275. I don't have a bottomless pit of cash though so we can't get crazy here. Is it a case of get the best I can out of the 998? Or forget about the 998 alltogether?

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Zulu...

1967 mini Cooper S

Everyone has tuned 1275s. There's sooo many of them.

I love a tuned 998, and the parts are cheap, including blocks and cranks!

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Unless you never go up hills I'd forget the 998 and start with a 1275, bore it to 1330 or 1360 but not bother stroking it.
Stroking costs more $$$ because:
Offset grinding crank adds $100
Wedging crank for better balance adds $~400
S rods need to be bought and narrowed to fit the crank, otherwise get new aftermarket rods.
Pistons need to be decked and their dish machined out a bit.

It all adds up, and at the end of the day it won't rev as hard (safely) as a stock stroke one will.

BTW I run one of each, see my sig line below.

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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.

If your going to build the whole drive train up (if you don't know what condition the diff and gearbox are in for sure you probably should get then checked over/rebuilt) you'll need to allow for that expense, say $1000 for a shop to do it.
Then you can budget for the build, (can other help with these prices);
Allow $200 for pistons and rings.
Over bore I think is $400.
New bearings, oil and water pumps.
Full gasket and seal kit/s.
I think that will do a std std engine build (including the over sized pistons).
Then you can start looking at what else you want and can afford. A cam could be $300, buying a 295 head or machining a 202 head plus new valves and springs if up sizing or spend 2-3k on a 7 or 8 port (fitted and basic tune).
Or you could go the boosted route instead or aswell as the head mods and add another few thousand for that lot.

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Respect mine and I'll respect yours.

IMO you have 3 options, big power boosted, high tec 7or 8 port, or a old skool mild to high tuned N/A 998 donk.

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Respect mine and I'll respect yours.