12 replies to this topic

[jeo022]

Morning!
Was just after a bit of advice, been searching old posts and found pros and cons for each but just wondered if anyone would recommend one over the other!?
I'm in the process of putting a 1275 maestro block into my mini, just had the crank reground, lightened and balanced along with the con rods and stuck a Kent 266 into it, the heads standard metro 1275 head but intend on getting some work done to this in the future! I currently have a weber 45 knocking about which I was going to use but have been offered a set of twin 11/4 carbs for next to nothing,
Intending to use the mini for road use, but mainly weekends so not an every day driver?!
Some guidance would be greatly appreciated!
Cheers in advance
Joe

[JakeJakeJake]

Deffantly go with the weber, twin 1 & 1/4's won't be big enough, especially if you intend to have some head work in the future.

However webers need to be set up on a rolling road but once set up they are done and need little maintenance compared to twins, you can get away with tuning twins without a rolling road if you know what you are doing but they "fall" out of tune and need adjusting a lot.

That said webers sell for about £180 a set of twins 1 & 1/2's can be found for about £120.

However a hif44 would be a practical choice they are cheaper, easier to set up, les maintenance, no bulhead mods (needed for weber) and more fuel efficient with not much of a loss in power. Its what I currently have on my 1380cc engine but it is a daily driver (don't ask how much fuel I use >.<).

[Timinichelsea]

A Weber is overkill for that engine, even with some head work done, especially if its for the road. Webers are pretty much race/track use only.

As said go for a HIF44, so much better for a road car.

[Cooperman]

I know a lot are going to disagree with me, but I would definately go with the twin 1.25" HS2's. If you look get a good manifold rather than the original BMC-designed one, the HS2's make up a fine induction system. The 266 cam is not too hot and at the rev range of that cam the 1.25" per pair of cylinders will flow fine, especially if you have an improved head and a nicely matched manifold.
Don't underestimate the twin SU's as fitted to the 1275 Cooper 'S'. They were fine in their day and on 1275 engines with a cam giving max power at below 6000 rpm there is nothing wrong with them.
I have HS2's on my Innocenti which has a 510 cam, 10.3:1 CR, 1330 cc and a 3-into-1 ex. manifold and it runs extremely well right up to around 6000 rpm.

[Native beats]

i'd listen to cooperman, ive been fortunate enough to of been in some of his mini builds.

Edited by Native beats, 23 November 2010 - 05:59 PM.

[mini93]

Webbers for me a 40 should be fine if you can get somewhere who can tune it properly

[samsfern]

you can get a set of twin hs4's to flow as well as a webber does if you know what your doing. twin 1 1/2"s would be my choice.

[cooperrodeo]

Twin SUs do not 'fall' out of tune and do not need adjusting a lot.

[Yoda]

I agree with Cooper man on this one, i would go for the twins, if they arein good condition, and as Cooperado says, "they do NOT fall out of tune," they may not set up properly if worn and some people assume that they are out of tune and fiddle with them. then blame the tuning.

If you are going to fit twins and you dont know their condition, get them rebuilt. Although i have Hs2's on my 1380, i feel this is only necessary because i run a 286 cam with a high compression, with your setup the smaller ones should be fine as long as you have a good inlet manifold.

You will find better torque at low revs and a really smooth pickup throughout the range once set up properly. and once set up, leave them alone and dont fiddle. Most probs with twins are worn spindles etc or manifold leak, NOT the carbs going out of tune. and the biggest problem with them is the owner who likes to fiddle.

[Cooperman]

It seems to be a common belief that the bigger the carb(s) the more mixture you will get and hence more power.
Howehver, the limiting factor is the cylinder head where the inlet tract goes through 90 degrees into the valve area. You can have much bigger carb chokes, but you still have that old limitation. Thus with larger carbs all that happens on a car with standard size valves, even witgh good gas flowing, is that the speed of the mixture through the carb is slower than with smaller chokes and thus the fuel has less vacuum to suck it through the jets. To get the inlet speed into the combustion chamber such that big carbs will work best requires a very well-flowed head with big valves and a lot of revs and thus a 'hot' cam such as a 276 or hotter.
As has been said so many times, to improve performance, you don't just bolt on a load of 'goodies', you match components to suit each other. Twin 11/4" HS2's are fine for a mildly-tuned 1275 if set-up properly. The carbs can also be flowed a bit if necessary.
On my 64 Cooper 'S' I have twin H4's and they work fine at the 117 measured bhp. I have had twin HS6's on an earlier 'S' which I used for rallying but they were no better than the H4's in terms of top end power and were not as good in the mid-range. I have built rally Minis with twin-choke Webers, but really never found any measureable improvement using the 286 cam. Maybe with a 296 or 649 at 7000 rpm it might have been different.

[JakeJakeJake]

Seeing as it is a road car so as much power as possible is not key a hif44 would be a better choice than twin hs2's, for the reasons previously stated. If it was for all out power then a hotter cam than the Kent 266 would be used. I am guessing you want a bit more poke without losing driveability and reliability.

At the end of the day it is personal preference twins will give better performance, sound better and look great but be a bit more expenive/more work, to buy, fit, run and maintain.

The weber would most likely be too much for your set up, also would either need a swan kneck manifold (not great for performance) or to cut a hole in the bulkhead.

Also although the twins are cheap, will they be needing a rebuild?

[jeo022]

Cheers for input, bulkhead on this mini has been done by the previous owner so this is no issue if I were to use a weber,
The twins however were only 1 1/4 and judging by the price would probably be in need of a rebuild of some description.
Am sure I have a hif44 knocking about somewhere too! Will dig it out and see what it's like!
Cheers
Joe

[JakeJakeJake]

Rebuilt kits are about £30-£40 and airfilters are about that aswell, you need two for twin carbs though. Not sure how much weber rebuild kits are.