I have a completely striped 998 engine and I want to rebuild it as a supercharged 998. I won't be running too high of a boost, I think 5-8psi would be around the most (but as we all know it might get increased over time ). I want the engine to last a long time.
Basically what should I upgrade during the engine rebuild? I was thinking a better cam to suit the blower, I already have slightly larger valves (not sure what size they are exactly, I can measure them) and double valve springs in a 998 head. I'm not 100 % sure but I think my compression is around 9 somewhere maybe even high 8's.
Should I try and lower the compression ratio by opening the head out and if I do have to re-bore it should I just get std pistons in the next size up or low comp ones if I can find them? (if I go a size up in the bore and keep everything else the same will that lower the comp ratio?)
Also I will lighten and balance everything aswell.

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Respect mine and I'll respect yours.

Get the crank and con rods crack tested, and if you want high revvs get things balanced. Lightening doesn't increase power, it just makes it easier for the engine to get spinning faster.

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Dean Hutton's first car was a Mini.

If you increase the swept volume with same head the comp ratio increases.. What set-up are you going to use blow or suck thru carby. On the Honda CBR forum the are some nice pics of a CBR1200 super-charged blowing thru a set of quad CR slide throttle carbys. The carbs are set into a box and sealed apart from air inlet from blower. They are now running at 30psi instead of 14.7psi [atmospheric pressure]

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

You should not need to lower the compression. But as David says if you increase the capacity without increasing the combustion chamber the compression will increase. So aiming for low 8's is a good idea for future possible boost levels. Around 9:1 compression should be fine with around 7psi, as long as the ignition isn't too advanced. Possible standard style low comp pistons would be good. Or talk to say GR about what he thinks as he seems to be the man for small bore pistons, or so I'm lead to believe.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

what supercharger do you want to run?
and what do you use the car for 99% of the time?

you wont need to drop the compression unless you want to increase the boost at a later time,

i would however rebore and fit new pistons and rings. normal pistons should be fine, but use good quality ones, i have RE pistons in mine.

if you want to lower the compression, take meat out of the head and pistons, increasing bore size will increase compression because you have more air and fuel to squeeze into the same size combustion chamber.

cam choice is pretty important, you can really make a pig of it with the wrong one. there are cams suited to turbos and these are the ones to look at if you want to race it or fang it on weekends.
otherwise a standard roady cam does the job.

you will want to upgrade your clutch, i have an orange dot in mine.

ARP rod bolts

drill the head for more studs, use ARP head studs or the like.

new oil pump, centre oil pickup

for reliability fit an oil cooler and a minispares 2 core radiator.

use a turbo head gasket

obviously you can spend a lot more if you want wedging and lightening..

its not really worth it unless you want big revs

mine has so much grunt i dont have to take it above 6000rpm and thats probably where you wanna be if you want it to last a long time.

with a huffer i find im able to drive with traffic shifting at very low revs and after 6 the power seems to drop off a little any way

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Enjoy Chris

My car makes max power a bit under 5 grand according to the rolling road dyno. But seems to work best if I shift around 5500rpm so that revs are right in the next gear.

In fact the car is nicest accelerating at about 1/2 throttle up to 3/4 throttle shifting under 4 grand. Makes for a smooth and reasonably quiet run while still being pretty quick.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

One thing you should look at upgrading (depending on what you've already got of course) is brakes , discs as a minimum , better pads if you already have discs .

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yeah good point! the whole car needs to be up to the increased power.

If you are using a 998\1100 head then you won’t really be able to put the extra studs in as there is no support there in a small bore head so your studs will be in the water gallery and crush the top of the head.

No such thing as a turbo gasket for a small bore but a good normal one (not copper) will be fine. Your CR rating I would be putting between 8.5 to around 9 but no higher or lower, it will be a pig with less than 8.5 unless you are running lots of boost(+15PSI maybe more), 9 is still safe with 8PSI ish, more if intercooled

ARP rod bolts are a good idea if you can find and afford them but not essential, just use cup head bolts.
I would be trying hard not to take any meat from the pistons as you want the crown as thick as possible and should be no problems taking enough out the head. Lightening your flywheel really doesn’t cost much but rods and crank will add you.

I’ve just gone throw the same problem of how far to go, as I’m building my new blow throw intercooled 998. After I get back from Melbourne next week I will post up my specs in my thread which may give you some ideas.

Hope this helps thanks Nathan.

The SC will either be a AMR 300 (300 cc of air per rev) I already have one but I'm having troubles with it, or I might get a SC12 (maybe an SC14) depending on what I decide to get as I'm still looking at them. The carby will probably be suck through as it's easier and cheaper.
The driving will probably be a weekend warrior driven regularly around town (fast ). I'm not after really high revs around 5000, 6000 if I accidentally hold a gear for too long or miss a cog as I'm nailing it .
The info so far is rather good, thanks everyone.

What I got so far is do a good quality rebuild, crack test rods and crank, open the head up a bit in the ports and in the combustion chambers, get a mild turbo cam that will suit the rest of the mods and do a bit of balancing and lightening.

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Respect mine and I'll respect yours.

Don't bother using a AMR 300 SC they are too small and have to be spun way too fast to get any boost then it still doésn't make any real power.

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4efte powered Clubman
supercharged 998 race car

Did you try one

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Respect mine and I'll respect yours.

Simple math.. the rpm it has to be spun to make the amount of boost you want is waayy to high and all the benefits of the boost gets negated by the amount of heat from the sc being put into the intake charge.

AMR500 on the other hand would be possible, but still, at the upper limits of the amount of air it can efficiently push...

I'm not going to disagree with you it's just ironic you have this quoted under your sig "boundaries are only formed by a limited imagination"

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Respect mine and I'll respect yours.