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first of all panky, the std twin su manifold is VERY poor design it flows about 94 c.f.m, you would be better off replacing it with an oselli torquemaster single 1 1/2 manifold 123 c.f.m , or even std mg metro 1 3/4 145 c.f.m. it wont breath well at all and wont compliment your cam.
however, if you really want to use it then as you probably know s.u,s are tuned on the needle and spring only. a good starting point for your spec would be AF needles and red springs.the springs should have a paint colour marking. the needles are readily available from burton fuel systems. best to get it on the dyno when its done to get it dialled in exactly, should be about 90-100 bhp.how is it coming on ?


"you were only supposed to blow the bloody doors off"
 
Thanks Tim, I don't want to go to extremes with this car and if I can get the twins working well with that glorious induction roar I will be a happy man (dreams of 60's Coopers batting down country lanes) :) I did contact Burlen Fuel Systems who said 'they couldn't possibly advise on tuning modifications' but now you've given me a starting point I'll order some needles and springs. Is 100 bhp possible with the twin 1 1/4's? that is more than I expected anyway (and about 50% better than standard engine), or would that be with the Oselli manifold mod. What needle and spring would you suggest for the original 1 3/4" carb ? (I've got to try it, it would be rude not to :)) It's coming on slowly but surely, only manage to work on the car for a couple of hours at the week end but I'm getting there.
I think my next venture into Mini building might involve an Eaton supercharger :p But not on this one I would like to keep it at least recognisable to the original car.
 
you might struggle to get 100 bhp on the 1 1/4 carbs. i really need to go home and check my needle chart for the bigger carb spec. also need to know if its hs or hif type su (fixed or sprung needles). eaton supercharger is a dirty word :D. i have 2 lurking, one keeps crawling towards the riley ;););).
keep up the good work [8D]

"you were only supposed to blow the bloody doors off"
 
Hi Tim, I've checked what is in the twins and they are FX needles but I can't tell what colour springs. The original 1 3/4" is fitted with a BDP which came with a stage one kit I fitted years ago. I also have the original BFY needle, I've swapped and changed a few times so I may have got them mixed up. The BDP and BFY are sprung needles. Burlen have the AF needles and red springs so once I get an idea for the bigger carb I'll send off for the lot :p

I know these are only a starting point, what others do you think I should look out for to fine tune. There are several lots on ebay at the mo :p
 
hi panky, best thing you could do is get the s.u needle chart book from burlen, its cheap. i still need to go home for mine. i should collect as many different needles you can if they are cheap, i have a box full collected over the years. off the top of my head, bda,bbc,bdt,bba,bdq sound familiar.
i personally would go with the single 1 3/4. i have in the past found a needle thats close and then dressed the relevant area with a needle file.
do you know about the s.u mod to the throttle bore to increase airflow [?]
i will post a pic of the manifold mod as well.:)

"you were only supposed to blow the bloody doors off"
 
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"you were only supposed to blow the bloody doors off"
 
Thanks Tim. Yes I've seen some carb mods somewhere, I thought it was in Vizards How to MYM but I've just checked and I was wrong again :(. I spotted some nicely done ones on ebay a while ago, I was tempted but I think I'll have a go myself and compare it to the twins. Thanks for the diagrams I'll definitely have a go at the manifold to get the best out of the TCs :D
Many thanks for the advice.
 
i have done quite a few s.u,s now and some amals for bikes like this and the difference is amazing [^], they suck soooooo much harder :p did a rover v8 and had to put dual green (the hardest) springs in to keep the slides down [:0]. one thing to remember if you knife edge the flutterby is leave the bit over the transition hole ;)

"you were only supposed to blow the bloody doors off"
 
Nothing worse than uncovering your transition hole [:0], even more disastrous than forgetting to squeeze your bulbous end [}:)]
 
Are you glad to see me or is that a just a grease gun in your pocket ( well it was funny last time :I[:eek:)]:I)
 
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