16 replies to this topic

[zebidee]

I'm trying to decide whether its worth changing to twins or not, and though there are a thousand threads on similar questions i just can't find out what i want! I've currently got a stage 1 1275 with stage 2 head, twin valve springs and an uprated cam, fueled by a single HS4. Firstly, what sort of difference do you really get out of twin carbs, is it worth it? Secondly, what sort of difference is there between twin HS2's and twin HS4's? And finally, do i have to chop up my bulkhead to fit any of them?
Cheers folks
Seb

[jaydee]

isnt hs4 too restrictive for a tuned 1275?
i'd go for twin hs2, or a single hs6
Twins give a better response to throttle and perform smoother than single carb, but personally i wont take used twin carbs, if one is worn will be a pain to set'em correctly (usually people are selling twins as they have troubles with the settings..)
Single carb is much easier to fit and set up.

[BoboGib]

On yours i'd go for twin HS4's, As long as its on a mini manifold you will not have to do any bulkhead modifications.

As mentioned twins give a better and smoother throttle respone but generally do not add any power.

A lot of people will tell you they are hard to set up, which is not all that true, unless as stated, one of them is worn more than the other. Setting them up is all about practice and having the right tools.

I have twin hs2's on my 998 and would never go back to a single carb unless I had to. After seing a power graph of mine after a RR session and one of Minilis' While hers had 1 bhp more with a single HS4, mine had a smoother power curve and held the maximum power over a wider rev range.

[Sleepy Stu]

HIF44 FTW

[AndrewJ530]

If you plan on modifying your engine anymore i'd probably be tempted to get twin hs4's/hif 38's but if you plan on keeping that spec now i think you would get away with a set of twin hs2's.

Basically it makes your engine pull smoother from lower down the rev range. I would only have a single if i had to (like BoboGib).

Again i'll back up BoboGib here, only if one carb is significantly more worn than the other it will be hard to set up. Plus any decent rolling road could easily set up twins.

[robh]

Seb
Twin HS4 are plenty, to use twin HS4 you need to be getting to a stage 3 head and a wild cam.
To fit twin HS4 get the standard mini manifold, no modifications needed. Go for pancake (K & N best) filters not the cone type they will hit the bulkhead.
Before setting up your carbs make sure the ignition timing is spot on and fit new plugs.
Setting up is not hard, some experienced people do it all by ear, I prefer a gunson colourtune to get the mixture right, and a gunson flow meter to balance the carbs.
Yes, it does involve fiddling about with little screws and a bit of patience, and you will spend a good hour revving your engine just listening and tweaking it.
And you have to go for a test drive, involving accelerating through third hard to check that the adjustments are good.

Enjoy..........................

[zebidee]

Thanks for all the info everyone! As for setting them up, i was going to purchase some used HS4's, strip them and then rebuild them, so this should make it far easier shouldn't it? Robh, if i was to run cone filters would the bulkhead need to be cut to fit, or could i use shorter spacers between the carbs and inlet manifold (did this on my single to get a bit of extra clearance). I only ask because i always thought that cone filters were more effective than pancakes??
Cheers
Seb

[davejf]

Hi,
I can't comment on the single v twins, because i've only ever had twins. Again, if they aren't worn and and set up correctly then there shouldn't be too many problems. I've got cones and they fit fine, no cutting needed. I would suggest Twin HS4 for the engine spec. before mine was rebuilt it had twin HS2's spec was 1310, MG metro cam and mildly worked head. at high rpm it was pinking. New spec is 1293, 286 cam with the same head and HS4's have solved the problem.

Dave

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[Dan]

i always thought that cone filters were more effective

Lots pf people think that. In a Mini it's not so simple, the bulkhead is so close to the carbs that it affects the flow into the filters quite a lot. Pancake filters actually seem to be a little more efficient than cones in a Mini. Get offset pancakes.

twin hs4's/hif 38's

HIF38s were never produced with a left hand body, so there is no such thing as a real pair of HIF38s. If you want a pair of smaller HIFs you will either have to find a pair of rare HIF4s or bodge together something of your own.

[zebidee]

Very tidy engine dave , this change of carbs began with me just giving my engine a lick of paint, its been filthy for far too long, funny how these things snowball!! Ok, well sold on twin HS4's now .Never seen 'offset pancakes', what are they like and where would one get some??
Seb

[jaydee]

Never seen 'offset pancakes', what are they like and where would one get some??
Seb

this is an offset pancake for hs4 carbs:
http://www.minispare.....PANCAKE FIL...

this is the corrispettive k&n filter (??)

http://www.minispare...=...FILTER 1.5

[Pooky]

Get twins with Pancake filters just for the looks and the noise!

[AndrewJ530]

Lots pf people think that. In a Mini it's not so simple, the bulkhead is so close to the carbs that it affects the flow into the filters quite a lot. Pancake filters actually seem to be a little more efficient than cones in a Mini. Get offset pancakes.

I'd would have thought that because the cones are bigger they can draw more air in. If you look at davejf's pic, even though they are closer to the bulkhead and stuff around it, there is more space above and around one of the sides of the filters. Just my opinion.

[Dan]

Offset filters just have the connection point offset to the bottom of the filter (in a Mini, I'd imagine other cars need them offset in different directions). It just means the filter clears the bulkhead properly as it lifts the filter higher.

[zebidee]

Ok, cheers! Just to add another complication, what about Webers, would one be a bit overkill ??