What makes a 998 really good ?

seandoyle · Post by **seandoyle** » Wed Feb 18, 2015 6:51 pm

Rebuilding my 998 Cooper engine & looking for your advice. I have a Brian Slark 12G940 ported & polished head 29/35 valves with 19cc combustion chambers(TBC).I also have twin 1.5 SU's which I would like to fit.It will have a re bore & crank re grind plus balancing.Any suggestions on cam,pistons wedging/blading & cross drilling. I will use Rob Walker for the work unless advised otherwise.Diff is 3.4 & I will use the car for Hillclimbing/sprints.Any advise will be much appreciated. I'm in the Epsom Surrey area & the fridge is always full of beer .

Post by **Simon776** » Wed Feb 18, 2015 7:28 pm

So I suppose sticking a 1275 in it isn't really the answer you are looking for?

LMM76C · Post by **LMM76C** » Wed Feb 18, 2015 7:33 pm

I inevitably wince when anyone mentions a 3.4 diff for hillclimbs, rallying and non-circuit sprints.
Of course for those in the south east a hillclimb is something recalled only as past history...

mk1coopers · Post by **mk1coopers** » Wed Feb 18, 2015 7:45 pm

LMM76C wrote:I inevitably wince when anyone mentions a 3.4 diff for hillclimbs, rallying and non-circuit sprints.

Yes but some of us just do it for fun and a personal challenge rather than to win championships, plus if you drive the car to events you need something that will let you cruise at a sensible speed without bouncing it off the red-line all the time

Post by **wantafaster1** » Wed Feb 18, 2015 8:02 pm

I'd stick with a well worked 12g295. 3.65 diff if you want to drive it on the road.

Chalkie · Post by **Chalkie** » Wed Feb 18, 2015 9:43 pm

Simon776 wrote:So I suppose sticking a 1275 in it isn't really the answer you are looking for?

1275 are over rated

Lord Croker · Post by **Lord Croker** » Thu Feb 19, 2015 12:53 am

Rob Walker has done some very good work for me, fully recommended

Regards, Rich.

Post by **Spider** » Thu Feb 19, 2015 1:54 am

wantafaster1 wrote:I'd stick with a well worked 12g295. 3.65 diff if you want to drive it on the road.

Yeah, I recon that's good advice, maybe consider a lower diff though, a 3.76 or a 3.9 and push the CR up to 0.01 before pop.

Other than that, fit an 1100 crank and some +0.100 pistons.

Chalkie wrote:
Simon776 wrote:So I suppose sticking a 1275 in it isn't really the answer you are looking for?
1275 are over rated

maybe, but 998s are so under powered.

Dr S · Post by **Dr S** » Thu Feb 19, 2015 7:54 am

You can get a nippy little car with one, mines at + 60, 12g295 with 28 * 32 valves. 10.2 cr Pocketed block, fully worked crank and fly. 997 cam, twin hs2 and cooper free flow. Made about 72bhp on the rollers.

Comfortably quicker than my fathers 1300 spitfire, slow as anything compared to owt modern. But fun to drive and that's the point right?

Chalkie · Post by **Chalkie** » Thu Feb 19, 2015 8:00 am

Spider wrote:
wantafaster1 wrote:I'd stick with a well worked 12g295. 3.65 diff if you want to drive it on the road.
Yeah, I recon that's good advice, maybe consider a lower diff though, a 3.76 or a 3.9 and push the CR up to 0.01 before pop.

Other than that, fit an 1100 crank and some +0.100 pistons.

Chalkie wrote:
Simon776 wrote:So I suppose sticking a 1275 in it isn't really the answer you are looking for?
1275 are over rated
maybe, but 998s are so under powered.

My ones just as quick as my mates 1275

he's stage one mines stage two

mk1 · Post by **mk1** » Thu Feb 19, 2015 8:48 am

I agree re the final drive, 3.4 is FAR to long. a 3.7 would be the best option. I used one for years in my roadgoing / Hillclimbing 1070 couldn't recommend it highly enough.

As far as cam choice is concerned, it's a case of how wild you want to go. My choice for this sort of engine would be a 276 type profile, maybe a 286 if you are feeling brave. I have not done much work on 998's for many years and I am sure that someone will be able to give better info re cams.

seandoyle · Post by **seandoyle** » Thu Feb 19, 2015 9:50 pm

Looks like the 3.4 is destined to life in the shed, & the fridge is still full ! Thanks for the advice so far.

Post by **rich@minispares.com** » Fri Feb 20, 2015 1:15 pm

that 3.4 would kill your car stone dead - it would be terrible for any sort of competition (unless your doing 'the most comfy 100 mile drive on the motorway cup')

my road 1071 runs a 3.7:1 and its perfect

my 1071 gtm runs a 3.4:1 and it has tall 13" wheels, its a great cruiser but was numb at blyton, it hardly saw 4th gear, even on the road it would be better with a 3.6:

my racer runs 4.3:1 and its epic - though I wouldn't want to drive it anywhere!

Post by **pad4** » Sat Feb 21, 2015 8:34 am

rich you run a 4 3.1 on a race car - were run 4 3.2 on the rally car and its out of legs so quickly - even blyton i had to watch the 8k red line all the time - tops out at 106mph i calculated - are you happy running those ratios cause i was thinking of changing mine to get a bit more speed out of each gear

Pad

mini63 · Post by **mini63** » Mon Feb 23, 2015 1:38 am

as i said on MCR forum on this topic i reckon the 998 performs well with mild improvements and attention to detail. The bottom line is plainly getting air in and exhaust out with a minimum of fuss. The head, filtration, cam and exhaust are key.
They are such sweet revver compared with 1275s.
A well sorted 12G295 head, an LCB exhaust and a 270 deg duration cam works well without a huge amount of overlap. About the only thing i should do is a lightened flywheel.
I have run this spec with 998 cooper pistons for ages using 4 sync 'S' ratios and a 3.44 final.

we here down under have vast distances to cover......

Admit though the 3.44 will kill a hillclimb/track car.

494TBBman · Post by **494TBBman** » Mon Feb 23, 2015 10:41 am

mini63 wrote:as i said on MCR forum on this topic i reckon the 998 performs well with mild improvements and attention to detail. The bottom line is plainly getting air in and exhaust out with a minimum of fuss. The head, filtration, cam and exhaust are key.
They are such sweet revver compared with 1275s.
A well sorted 12G295 head, an LCB exhaust and a 270 deg duration cam works well without a huge amount of overlap. About the only thing i should do is a lightened flywheel.
I have run this spec with 998 cooper pistons for ages using 4 sync 'S' ratios and a 3.44 final.

we here down under have vast distances to cover......

Admit though the 3.44 will kill a hillclimb/track car.

About 1976 I did my my 1969 Mini 1000 power unit, rebuilt engine and used AEA630 cam, skimmed 12G295 head, duplex timing gear, Mini automatic 1 1/2" SU with automatic manifold. The gearbox already had a 3.44 diff from standard. Performance and economy was not at all bad. Was good for motorways. Don't know how much power it put out, but it was a great improvement on the standard setup.

Engine is still like that today, but car is not in use.

Chalkie · Post by **Chalkie** » Mon Feb 23, 2015 2:42 pm

Ill be using the 276 cam on my current 998 build alot of good reviews bit lumpy down low but great pull from 1500 rpm if not go for the 266 cam bit lower down but then not as much top end (reading off minispares)

Post by **rich@minispares.com** » Tue Feb 24, 2015 8:18 pm

pad4 wrote:rich you run a 4 3.1 on a race car - were run 4 3.2 on the rally car and its out of legs so quickly - even blyton i had to watch the 8k red line all the time - tops out at 106mph i calculated - are you happy running those ratios cause i was thinking of changing mine to get a bit more speed out of each gear

Pad

You can't blame me if you have such a low red line..........

vulcanbb18 · Post by **vulcanbb18** » Thu Feb 26, 2015 11:17 am

I've recently got an '72 Oz clubby van on the road with a worked 998

Still early days with this engine, but so far very impressed, spec is :

1022cc, 731 cam (5 deg adv), 9.5:1 compression, 295 head ported with (small) 1275 valves, 1.3 roller rockers, HS4 (AAM needle) on minispares manifold & K&N cone filter, lightened std flywheel, goss mech fuel pump, regraphed hitachi dizzy, 4-sync box with 3.65 diff, maniflow freeflow extractors into an RC40.

Engine hasn't even seen 5000 rpm yet (still running in), but at WOT it gets there damn fast! Nice exhaust note too

cheers,

Jacob

Thu Feb 26, 2015 11:25 am

that will go like a cracker!

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