Spare 998 plans
Turbo Mini Forums

So I have a 998 in my garage that I have taken out of my project, the car is going 1293 turbo so the engine is going spare.

The 998 in my daily driver is starting to wear a bit, leaking like a bitch and costing me loads in oil and driveway cleaner, gear box crunches in 2nd when cold and it's generally just in need of a freshen up.

The spare 998 I have is pretty bloody solid and I thought I can build it up for a little power gain and then do an engine swap over a weekend.

I've been offered a set of twin 1.25" SU carbs for £125 (which I know will need to be set up on a rolling road) but anything else that is cheap(ish) that I can do for little bit of driveable fun?

Pocket the block and plonk on a 940 casting head.

Change the cam.. this is what causes he 998 to run out of torque, power and everything else including the will to live at 4500rpm.

I thought about different heads and cams but how much would pocketing and a head cost?
I want this to be cheap, ideally no more than a few hundred quid.
And what cam would you recommend? a Kent 266 for performance with driveability?
Would you say a new cam would be one of the more "important" parts for tuning the 998 or is there anything else that can release a bit of the power.

Cheers for the response Sam.

Have a look at the you tube link in Robert's signature. There is a video of him pocketing a block. doesn't look difficult.

na mg metro cam works well in a 998

You're right actually, doesn't look too difficult at all.
I just don't have to tools and, if I was to go down the 12G940 head and pocketed block route, I don't know whether it would be worthwhile buying said tools or just paying to get it done.

On the look out for an MG Metro Cam, cheers Haz

Edited by DaveVader on 21st Nov, 2010.

12G202 + some head work and a skim + a cam (260ish) and a stage 1.

With those, I believe your banana output should fairly exceed a 1275 low comp and might come close to the output of a late Cooper carb.

(I hope so 'cos it's what I am gonna build until I finally buy a house and start to weld my turbo manifold)

Rusty by nature

get one of these,

http://cgi.ebay.co.uk/NEW-CHALLENGE-1200W-...=item3a5cee24c3

then make some shelves after...

just stick some nitrous on it?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

hmm, I fucking love bananas!

Got an LCB on the daily at the moment so that will be staying.
Looking at Kent cams on minisport as they will be within my price range and then will have a chat with a guy I know about skimming etc.

If I don't get a different head, I'll just skim the one I have.

Ninja edit:

Everyone likes a good shelf.
Although having a router could actually come in handy. Is that one any good or is it a case of, get what you pay for?

Edited by DaveVader on 21st Nov, 2010.

So far I have decided...

Swiftune SW5 Cam with double valve springs.
Twin 1.25" SU Carbs.
12G940 Head with pocketed block.

Anything else I should change or uprate? I mean it's not an intensive build so would presume I don't need things like a centre main strap, better clutch or gearbox.
What about rocker assembly? Valves? Pistons? Rings? I think I've got duplex timing gear but will check on the strip down.

I'll be replacing bearings and gaskets and such things.

I've set a budget in my head of £500 (not including tools) so would like to stick to it so if you do suggest anything then make sure it is a necessity or cheap.

Before I went turbo my 998 had an mg 12g940 Swiftune sw5 cam cooper freeflow manifold Maniflow exhaust electronic dizzy and standard 1 1/2 su and airbox with a k&n reacement filter. 73 bhp on the rollin road but the rest of the Motor was tip top aswell fully rebuilt. Fully ballanced with centre main strap and arp rod bolts for extra security. I wouldn't bother with the twin su carbs stick with the single and put the extra money into building in reliability

That mini is determined to Kill me!!!!

Twin SU's already bought due to their bargainous price. I'm sure things like centre main strap and ARP bolts can be bought for myself as... say... an xmas present, meaning my budget is still in tact. lol
I have just added it up and it has come to, with centre main strap and ARP bolts, £441.68. Not bad. But then there's machining work etc. :\

It's nice to see someone has done a pretty similar build, did you use yours as a daily? What was it like in traffic? And when you opened her up?

The twin SU as a bargain is always a good way to get money on it selling it back ...

I am not too keen on a 12G940 on a 998.
I didn't built one, never been in one but one thing I know is you can't go back on machining.
So once your block is pocketed you can never fit a small bore head on it.

What is more the price of good 12G940 is going up, not too good for a budget build.

Finally, I believe that big valves need longer cam to be used to their full extend so maybe a SW5 is not the perfect match for this set-up.
But maybe I am wrong seeing bigmini's setup and results

Rusty by nature

ugh, this is so difficult to select the right bits.

just stick a hif44 on it, better in every sense bar looks

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

I was told that if you have pockets machined into the block you can still use a standard head.
Do you really need a center main strap?

yep you can put the 998cc head back on a pocketed block. They use the 998 head gasket as the template and the pockets dont go outside the gasket line. just slightly lower compression unless you skim the head a bit more. For turbo aplications i would strap the centre main it dosent really cost that much to do but do get it dome properly not just a geezer with a mill they do need to be surface ground and the crank jounal bore rechacked

My small bore turbo project http://www.turbominis.co.uk/forums/index.php?p=vt&tid=473901

A centre main strap is needed more on a high reving NA motor then a high torque turbo motor. So not really essential.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Question about strap.

On 1275 you use Metro Turbo main bearing wich gives more strenght to the bottom end.
But on SBU, you just have to do with the standart setup unless you fit a strap.
I have not read anything about the mains letting go on turboed 998 but did you H brother did it to your hill climb ?

Rusty by nature

The hillclimber does have a strap, but it is 150bananas. Even so it is not the bottom end that takes the hammering on a turbo is it is not as necessary as you might intuitively think.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Bottom end, I just thought BL's worked on it when working on the Metro turbo so it might be required.

But maybe the 998 main bearing cap is beefier ?

Rusty by nature

Have a read of the metro turbo myths thread. The metty turbo bottom end is nothing special.

There is nothing special about the 998 cap either.

Very basically the turbo motor makes more torque by burning more air/fuel. This means the gas expands for longer and is still pushing the crank when it is 90deg past TDC. This is why turbos make more torque and don't put much extra stress the bottom end. As stated it is revs that kill cranks not turbos.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

I was just talking about mains ...

I red in Vizard they were specific and gave more strenght to the bottom end ...

Rusty by nature

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=4724

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.