Twin SUs or Weber 45 DCOE?

[W1NG3D]

I'm currently running a single HS4 1.5" SU carb on my 1293 engine, and am considering upgrading it either to a twin 1.5" carb setup, or a Weber 45 DCOE. However I'm just wondering what the benefits and drawbacks are of both of these potential setups, and which one would be the more effective upgrade.

The engine is from an Austin/Morris 1300 but has been fully rebuilt, bored out +20 to 1293, and fitted with a cam ground to ST948 specs. I've also recently had a Stage 1 kit fitted (but not the needle yet). It has a good power band and pulls the car along nicely, but I wouldn't mind getting a bit more out of the engine and making it more responsive. Basically I'm trying to decide which carb setup would be better to invest in; I already have some 1.5" SUs from an MGB, which with the right parts, a rebuild kit + a new manifold I could adapt to fit the mini. For a similar cost, I can also get a hold of a complete kit for fitting a Weber, including a short manifold which doesn't necessitate any bulkhead modifications. Of course I'd then have to source the carb itself, but I'm in no hurry to upgrade.

I'm not terribly concerned with keeping the car looking original under the bonnet, as I've already strayed away from the factory specs by "Cooperising" what was originally an 850cc mini. That said, I do think the twin SUs really look the part in a mini engine bay, but I don't mind sacrificing a pretty engine bay if it means the weber will offer better performance.

Any opinions and advice on which setup would be better is much appreciated.

[Spider]

Both SUs and Webers are very good carbs, but like many things, horses for courses. For a street car (which does sound like yours), SUs every time.

The SU being variable choke is better than the Weber across the board, except when they get to their upper ends of air flow, where the Weber is usually better.

With the twin 1-1/2's would go well on your engine and on paper are a suitable size, if it were me I'd actually probably go for twin 1-1/4's (if I was to go for twins), though I do have an engine of similar spec to yours and I run a single HIF44 on that. In the lower and mid range - where i tend to 'live' most of the time, it makes the car more drivavble (easier to live with) and uses next to no fuel, but it does loose out a little on the top end of what the engine is capable of, but I only use that end of things every so often. Shortly after I first built this car, I did run with twin 1-1/2's and while it was 'fun' I am enjoying the HIF44 far more.

I'm not entire sure what the Manifold Angle of an MGB is (someone here will know), however you may also need to change the float bowl angle to suit installation on a Mini, if you are to run with those Carbs.

[W1NG3D]

Both SUs and Webers are very good carbs, but like many things, horses for courses. For a street car (which does sound like yours), SUs every time.

The SU being variable choke is better than the Weber across the board, except when they get to their upper ends of air flow, where the Weber is usually better.

With the twin 1-1/2's would go well on your engine and on paper are a suitable size, if it were me I'd actually probably go for twin 1-1/4's (if I was to go for twins), though I do have an engine of similar spec to yours and I run a single HIF44 on that. In the lower and mid range - where i tend to 'live' most of the time, it makes the car more drivavble (easier to live with) and uses next to no fuel, but it does loose out a little on the top end of what the engine is capable of, but I only use that end of things every so often. Shortly after I first built this car, I did run with twin 1-1/2's and while it was 'fun' I am enjoying the HIF44 far more.

I'm not entire sure what the Manifold Angle of an MGB is (someone here will know), however you may also need to change the float bowl angle to suit installation on a Mini, if you are to run with those Carbs.

My car is definitely a street car, and it is my daily driver, so drivability is pretty essential. And going by what you've said, it sounds like the SUs are more likely to offer that over the Weber.

MGB's twin carbs are the wrong angle (I think they might be 10 degrees), so I will definitely need to change the float bowl angle to suit a mini manifold, and I'm happy to do that since I'd have to fully refurb the cars before fitting them anyway. They came off a 1967 MGB GT which was absolutely 100% original (right down to the magnetic Kangol lap belts), so having never been restored I'd imagine the carbs are a bit tired.

[Sean1380]

TBH and in agreement with the comment above.

For a street car, the HIF44 on a Mini Spares Alloy inlet rocks, it may not be as pretty as a set of twins, but the HIF is fuel efficient and they produce the power.

My 1380 with Mini Spares EVO cam, high compression and big valve head gave me 7 litres per 100 kays on a 1,200 round trip from Durban to Johannesburg a few years ago, and we were sitting at or above the legal speed limit most of the way.

In perspective, my Renualt Clio3 1.4 gave me 7.9/100 on my recent trip from the coast (Durban) up the the Highveld (Jo'burg)

[Sean1380]

just been to ...

http://www.calculateme.com/cGasMileage/ ... perial.htm

and that works out to over 40 miles per gallon for my 1380 with the HIF44

[Spider]

just been to ...

http://www.calculateme.com/cGasMileage/ ... perial.htm

and that works out to over 40 miles per gallon for my 1380 with the HIF44

I'm too lazy to do the sums, but I can get, without trying, over 750 km from a fill (~50 litres) in the car that has the HIF44, mind you, put the boot in and,,,,,,,,,,

[Spider]

Just one other thing I'll add regarding the Weber: Every Mini I've been in that had one sounded faster than it really was, Perhaps an unfair comment and just my own general observation. As I've said, Webers are a good Carb and I've had some experience with them both Street and Track.

My car is definitely a street car, and it is my daily driver, so drivability is pretty essential. And going by what you've said, it sounds like the SUs are more likely to offer that over the Weber.

To be fair, let's see what some of the other guys say.

[W1NG3D]

just been to ...

http://www.calculateme.com/cGasMileage/ ... perial.htm

and that works out to over 40 miles per gallon for my 1380 with the HIF44

That's a pretty impressive economy figure for a performance engine, I must say! Just another reason why minis are such great cars. Even after upgrading the engine, I'll still be getting better economy out of this 50 year old car than I did with my 1995 Toyota Celica SSII, and as long as it's better than that car I'll be happy

[Cheeser]

Yes generally agree with the above comments to go with SU, either single hif44 or twin hs4s.
Main thought is that a good manifold and filters are important together with proper set up on a rolling road with someone who knows how to tune SUs with suitable needles.

[rich@minispares.com]

Just one other thing I'll add regarding the Weber: Every Mini I've been in that had one sounded faster than it really was, Perhaps an unfair comment and just my own general observation. As I've said, Webers are a good Carb and I've had some experience with them both Street and Track.
.

I think that sums them up!

I would go for twin su's over a sidedraft weber every time on a road car, for ease of fitment, tuning, economy, cost etc.

webers have their place if your doing competition or looking for very specific and endlessly tuneable 'lumps' of power/torque - but for every day use a su will win hands down


it is horses for courses though, and some people will argue the polar opposite!

[Vegard]

A 45DCOE is of NO use with that camshaft.
I'd fit twin Hs2s. Prettier and more responsive than a Hif44/HS6. Who cares about fuel consumption on the Mini?

[In the shed]

Weber does sound a bit OTT for that cam.

Fit a more hairy cam!

Nothing up with race engines on the road, as long as you're not doing rush hour city traffic stuff!

[Dr S]

Webers do just look right, my vee dub camper runs a pair of 40's on high raise manifolds opening the bonnet is a pleasure

The mini will get one for it's 1050 at some point. Albeit probably a 40 not a 45..

[evonaut]

nothing wrong with seeing these when you open the bonnet!

[Dr S]

Touché!

[mikep]

I am probably a bit out of date but years ago (old fart I know) the consensus used to be that webers were not as good as SU without bulkhead modification. Reason was that the SU sit more or less inline so a short manifold was little disadvantage whereas the Weber had to run a short curved manifold which didn't flow as well. Maybe things have changed now but I can't see it will make much difference either way.

[Vegard]

Twin HS4s are equally stupid on that spec.

[coop12g295]

And split 45s look sexy and in line

[carbon]

Twin HS4s are equally stupid on that spec.

I'm with Vegard on this one. A pair of twin HS4s would be better matched with a longer profile cam with more valve lift, as the real benefits only kick in at high rpm.

The OP's engine spec is a good tractable fast road unit.

I would recommend sticking with a single HS4, fully vizardised inside, with K&N filter (pref not cone) and good stub stack (not rubbish cheap one from ebay). And spend the money on a good flowing inlet manifold similar to Oselli Torquemaster, getting flow from good shape not large ports.

With this set-up you won't be giving away many horses as compared to twin HS4s or Weber.

[W1NG3D]

Thanks for all the input guys. I'm leaning towards twin SUs at the moment, but I appreciate the feedback in regards to the benefits of a single carb setup.
Just another question though - I'm also considering fitting high lift rockers, either 1.3 or 1.5 ratio, so would this upgrade make better use of the twin SUs? I'm not too clued up on these rockers but from what I've gathered, it offers a similar performance boost to fitting a livelier cam?