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Car Forum / MINI / August 2004Worth fitting a 998cc with twin 1 1/4" SUs?
I have the opportunity to acquire a good set of 1 1/4" SUs and am considering using them on my 1990 998cc, 73k on the clock. Could some of the chaps amongst you with relevant experience of such set ups do me the honour of giving some pointers on the other recommended modifications to a 998 to make the use of twin SUs a worthwhile addition. Many thanks in advance Sean Hamerton, Brighton > I have the opportunity to acquire a good set of 1 1/4" SUs and am > considering using them on my 1990 998cc, 73k on the clock. [quoted text clipped - 7 lines] > > Sean Hamerton, Brighton Most people will probably tell you that twin SU's usually aren't worth it from a performance point of view. The main reasons being that a single SU will usually flow better; the twins usually cost more, they certainly cost more to service, you also have to buy 2 airfilters; they are also more difficult to set-up and tune and your insurance company will probably up your premium. There is only one real advantage, and that is the fact that you have twin SUs, and as everyone will tell you, they are one of the coolest things on the planet. I'm not sure what your current carb is, it's probably a 1.5" SU, but could be the older HS or the newer HIF. If it has a seperate float chamber it's an HS and would benefit to being upgraded to a HIF which flows better. I'm not sure how these 2 both compare to the twins in terms of airflow to the twins but if they are not better, there will not be that much difference. If you go with the twins you will need the correct inlet manifold and you will need a new exhaust manifold (the old one won't fit). The exhaust manifold depends on what else you are planning to do to the engine, usually a LCB is recommended for most stuff. You will also need to have the carbs set up with the correct needle and spring. You should get a freeflow exhaust too. If you do all that you will see a performance increase, althogh it will be more down to the manifolds and filters rather than the carbs. If the twins do flow better than a single 1.5 (and I don't think they do but someone might correct be on that) you would probably need to upgrade the head to actually see any performance increase from them. Modified heads are expensive but will be unleaded and all ready to bolt on, old heads of 998 coopers and the like are cheaper but will probably be leaded and will require a clean up/rebuild. Unless you want the twins for kudos value (and who could blame you?), I personally would make sure the carb is a 1.5" HIF. Get an airfilter, inlet and exhaust manifolds, and freeflow exhaust system. You can buy all of that (cept the carb) in the form of a Stage 1 kit which are about ?150. It comes with the right needle (roughly, still should have it rolling roaded really) and they say it gives you about 20% extra power. Hope that helps Dave > > I have the opportunity to acquire a good set of 1 1/4" SUs and am > > considering using them on my 1990 998cc, 73k on the clock. [quoted text clipped - 14 lines] > are also more difficult to set-up and tune and your insurance company > will probably up your premium. I had twin 1 1/4"s on my 997 Cooper (this was back in 1984 to 86!), both the original ones with the 997 engine and another set on the overbored 998 lump (with alloy head! :-D ) I replaced it with. They are absolute b*st*rds to set up - although I managed to balance them myself with one of those cheap pipe things that you listen to, I couldn't get the jets/mixtures right and had to get it done professionally. > There is only one real advantage, and that is the fact that you have > twin SUs, and as everyone will tell you, they are one of the coolest [quoted text clipped - 22 lines] > heads of 998 coopers and the like are cheaper but will probably be > leaded and will require a clean up/rebuild. With a good manifold twins *will* flow better as the flow will almost be direct/straight into the head inlet ports - which has got to be better than 90 degree bends on some cheap single HS4 manifolds I've seen! > Unless you want the twins for kudos value (and who could blame you?), I > personally would make sure the carb is a 1.5" HIF. Get an airfilter, > inlet and exhaust manifolds, and freeflow exhaust system. You can buy > all of that (cept the carb) in the form of a Stage 1 kit which are about > ?150. It comes with the right needle (roughly, still should have it > rolling roaded really) and they say it gives you about 20% extra power. 20%? Only 20%? My home built/tuned 998 with twin SUs would see off my brothers Mk3 Cooper 'S'! >> Unless you want the twins for kudos value (and who could blame you?), >> I personally would make sure the carb is a 1.5" HIF. Get an [quoted text clipped - 6 lines] > 20%? Only 20%? My home built/tuned 998 with twin SUs would see off > my brothers Mk3 Cooper 'S'! Sorry, the 20% is what most stage one manufacturers quote as the power increase over standard. If they do flow better as you say, the difference will not be massive unless he has higher than a stage 1 really cos the carb is not the weak link in the chain so to speak. As you say though your car with bored block and a nice head should be faster if the flow better cos yours needs the extra air. I guess it depends on the OPs intentions for the rest fo the car. If he can get a pair for a decent price then it can't do any harm and it leaves him open to beef up the engine in other departments without worrying about the carb for a while. On the other hand, its not worth bolting a set of twins on a standard engine, for the money and effort he won't much improvement. Unfortuneatly I never have enough to spend on nice stuff so I prefer to start at the bottom with stage one, sort out the weakest part and claim your cheap and easy power gains before moving on to the other stuff. <snip> Twin 1 1/4" SUs in clean and faultless condition bought on ebay with brand new K&N pancakes, heat shield and manifold for ?61. To tell the truth, my intention was to see if it was worth playing with them on the 998 until I get hold of a nice 1275 to rebuild and drop in there, which would have these carbs upon completion (they came off a Clubman 1275GT). The plan is to gut the 'bay, get rid of that bollocks soundproofing crap foam and make everything look pretty with lovely shiny dashpots and filters crammed in there. Thanks chaps > The plan is to gut the 'bay, get rid of that bollocks soundproofing > crap foam and make everything look pretty with lovely shiny dashpots > and filters crammed in there. > > Thanks chaps Go for it then, nothing looks quite as good as twin SUs in a nice engine bay, if you ask me. > <snip> > [quoted text clipped - 5 lines] > which would have these carbs upon completion (they came off a Clubman > 1275GT). Well they wouldn't have been original on a 1275GT - they had a single 1 1/2" HS4. > The plan is to gut the 'bay, get rid of that bollocks soundproofing crap > foam and make everything look pretty with lovely shiny dashpots and filters > crammed in there. Be warned that a pair of SUs with pancake filters *can* make a lot of noise! Hope you've got some good ICE or earplugs.... <snip> > Be warned that a pair of SUs with pancake filters *can* make a lot of noise! So I've heard, but as you can probably guess, by choosing to drive a Mini, a bit of induction noise isn't likely to bother me... Sean > <snip> > [quoted text clipped - 3 lines] > So I've heard, but as you can probably guess, by choosing to drive a Mini, a > bit of induction noise isn't likely to bother me... I used to have ears like that 'when I was a lad'..... ;-) > > <snip> > > [quoted text clipped - 6 lines] > > I used to have ears like that 'when I was a lad'..... ;-) If I want speed, comfort and quietness I drive my dad's leatherclad Laguna II 2.0T If I want to DRIVE I take the Mini well in my opinion the twin 1 1/4 are ok BUT you need to let the motor flow lcb 1 3/4 inch exhaust any bigger you start to lose back pressure then you lose power ...... clean the chambers a bit clean up the dags and crap in side the ports inlet and out let ..... gunsen's don't know if ya got em over there but it is a thing for ballancing the carbs ....... needle's well that would be something either to get set up on a rolling rd or talk to a few tuner's and see what they recomend ......... i did this on my first mini a 75 clubby with a 998 init once we set the carbs up properly made abit of difference especially mid and top end .... hey do you guys have the nissan pulsar over there 88 92 mod's ?? makka > > > <snip> > > > [quoted text clipped - 12 lines] > > If I want to DRIVE I take the Mini <snip> Yes, I've been reading Calver's Corner on www.minispares.com and I've got a very good idea exactly what to go for now. Sean |
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