10 replies to this topic

[BUCKERSMINI]

Hi I have just been given a CT swan neck manifold. I already have a weber 40 dcoe for my next engine project. It's going to be a fast road spec would fitting a swan neck restrict performance in anyway?
Thanks again

[Cooperman]

The swan-neck manifold is a very poor design.

If you don't want to cut the bulkhead and fit the 'Weber box', you will be better off with twin HS4 SU's on a decent inlet manifold.

For a 'not quite so slow' road Mini that would be ideal.

A Weber is really only a good advantage on a race MIni where a few tenths of a second per lap are needed.

[timmy850]

Here is a (potentially misleading) article with some dyno numbers comparing a 40mm Weber on a normal manifold to a Swan Neck one (as dyno figures are uncorrected).

http://www.minimania...ld_Combos_Weber

 

 

 

 

 

The Swan Neck is a manifold that a lot of people like to run down, but for the small bore road engines, making up to 90hp, it works very well. It has excellent throttle response, because of the small volume and high air speed, and is a very good manifold for road car use, with the 40mm Weber and 34mm chokes. However, it is not really suited to the 45mm Weber.

 

Edited by timmy850, 27 June 2016 - 11:55 PM.

[Spider]

I would also agree that if you are hell bent on running a Weber, the Swan Neck is not nearly as bad as it's made out to be. It may only loose out in the upper end of the engine's toque band, but most other places, it would be on an equal footing or better.

 

Webers don't seem to atomise the fuel as well as an SU at lower air flows and for a street car, this aspect should be given due consideration. I've always found that street Minis that run Webers, cylinders 1 and 4 run rich and 2 & 3 correct or lean. This I put down to the poor atomisation that these carbs give at lower (read: Street) air flows.

 

Timmy, this chart has been kicking around the internet for a few years now;-

 

Here is an article with some dyno numbers comparing a 40mm Weber on a normal manifold to a Swan Neck one. 

http://www.minimania...ld_Combos_Weber

 

 

 

 

 

The Swan Neck is a manifold that a lot of people like to run down, but for the small bore road engines, making up to 90hp, it works very well. It has excellent throttle response, because of the small volume and high air speed, and is a very good manifold for road car use, with the 40mm Weber and 34mm chokes. However, it is not really suited to the 45mm Weber.

 

 

 

But is VERY misleading and quite meaningless.

 

The parameters of the test (?) engine are not included with it and if in fact the head in particular was set up to take advantage of any one of those manifolds that could also disadvantage the others.

 

But more so, the figures are not corrected and the factors not included so corrections can be applied, so it's really a work of fiction, I guess to push someone's wheelbarrow.

 

Did someone post here just recently (to the effect) 'I read it on the internet, so it's gotta be true' ?

Edited by Moke Spider, 27 June 2016 - 09:56 PM.

[timmy850]

I figure some actual dyno charts are better than not having them at all? Yes, it might not be the best, most accurate set of data.

 

It is helpful to show that maybe all swan neck manifolds aren't crap, and might be worth using. If you have them in your stock, and want to run a Weber, and don't want to hack up the firewall to get it to fit it is a reasonable option (but not the only option). It would be much cheaper than leaving them aside & buying a good nick set of twin HS4's. (Or cheaper than buying a new short Weber manifold).

 

There are three parts to that series and have lots on info, including the head. Of course just because you've tried different combinations on the same engine doesn't mean you've necessarily spent time trying to get them all spot on. 

http://www.minimania...ll_Bore__Part_1

http://www.minimania...__Cylinder_Head

http://www.minimania...ld_Combos_Weber

Edited by timmy850, 28 June 2016 - 12:01 AM.

[Dusky]

I wouldn't use the swanneck manifold for some reasons.

First and best reason is that there are other, better flowing manifolds, wich can be fitted without cutting your bulkhead . :)
The maniflow 3 inch one is an example, as is the old cannon alloy inlet. I had the cannon inlet 

 

2 reasons not go get a weber on a road mini :
How will you plump the crankcase ventilation?
How will you plum the dizzy vacuum advance?

Especially the first, crankcase ventilation, is an important thing. Leaking crankcase fumes make you smell really bad. Not something you want when you use the mini to go to your girlfriend ;)

[monkey]

Can't you drill at tap the manifold for dizzy advance and crankcase ventilation?

I'm sure on the su both are after the butterfly and jet so don't see any difference between that and tapping the manifold?

Never done it, just my thoughts.

I disagree about the girlfriend though, if she don't like the smell of mini she ain't worth keeping!

(Don't tell the wife I said that - she thinks the mini stinks)

[Spider]

You can drill the Manifold for Crankcase Ventilation, but will only ever be a PCV type, not really as good as the CCV that the later SUs have.

 

The best place for the Vac take off for the vac Advance is in line with the butterfly so there's no advance added at Idle. No wonder some of them run on. The HS series and and earlier carbs were like this and I actually re-drill the HIF types and reposition the Vac take off on them.

[nicklouse]

Blah blah blah.

Yep run most carbs over done time on a road car,


For me any road A series would have a well sorted manifold and a single SU. Would not bother with twins would not bother with a DCD would not bother with a 40 of 45 Weber or Delorto.

But that is said by someone who is happily running a 48 IDA on a race car.

[Spider]

I figure some actual dyno charts are better than not having them at all? Yes, it might not be the best, most accurate set of data, but

 

Sorry, I'll clarify my early post and add to that that even between manifold types listed there, the results between each column cannot and should not be compared to each other. Even if the testing was done in the same day, on the same dyno, conditions during the day change that will change the numbers, so, between each other, they are fictional and not comparable. It is very misleading.

 

By allowing for corrections, the figures could easily change by as much as 20% even in the one day.

 

It's worse than not having any numbers, it's misleading.

 

Nick - I ran out of likes for the day (why is there a limit?), but consider your post ^ 'liked'.

Edited by Moke Spider, 27 June 2016 - 10:26 PM.

[Dusky]

Can't you drill at tap the manifold for dizzy advance and crankcase ventilation?

I'm sure on the su both are after the butterfly and jet so don't see any difference between that and tapping the manifold?

Never done it, just my thoughts.

I disagree about the girlfriend though, if she don't like the smell of mini she ain't worth keeping!

(Don't tell the wife I said that - she thinks the mini stinks)

Manifold has a constant vacuum, not quite the same as Just after the butterfly

There 's a thread about this on the mg forum

Ha, she paints my engine Block and times the cam for me so I have to keep her
Inhaling very toxic fumes wasnt on my 'todo ' list anyway