13 replies to this topic

[adamg1380]

Hi all,

I'm after a bit of advice or opinion about split Webers - I've had a search on here but mainly found people asking about sticking them on road cars. I'm currently gathering bits to turn my dual-purpose road / sprint car into a dedicated sprint, hillclimb and track day car, the time has come to go beyond road-drivable spec.

I've been offered a Longman split Weber 45 DCOE set up, including manifold and linkage. I was originally planning on a single (twin choke) 45 DCOE, but the splits are being offered at a good price and came off a known working engine, which ran the head I'll be using and probably the same cam.

So, price aside what are the pros and cons of a split setup vs the single? If the price is right, any reasons not to go for it? I'm assuming setup is no harder apart from the balancing? I'm especially interested in what anyone who's run both setups has to say.

Overall spec of the new engine will be 1380 A series, good bottom end, 286 or maybe 296 cam, MED head with 37/30 cut away valves, high lift rockers and the rest to suit. It's now a competion car only, no road use except the few miles to the MOT station (I'm in a road-going class) or a quick shake (literally!) down and brake cleanup.

Cheers,

Adam

[Paul Wiginton]

I and others I know have had better results from single 45s.

I know theory is good having a straighter run into the head giving better fuel distribution, but in reality the single is better. This is backed up by Pete Baldwin and Nick Swift and Southern Carburettors

Paul

[Sherlock]

If the price is right, go for it, kept in good nick, split Webers are an investment & I'm sure you can get them to work for you in the meantime, there is a lot of discussion about splits or a normal 45 DCOE, I know people who swear by both. I've always been led to believe that one of the advantages of splits was that you get double the float chamber capacity, improving fuel flow & reducing surge, but that did come from the Rallying fraternity where requirements are slightly different & which may explain why the works team used splits in the latter years of the Rally Cooper 'S's

[adamg1380]

Hmm, I'm still not quite decided, but I may go for these, for two reasons:

- They're off an engine that's virtually identical to mine, so should be set up ready to go.
- I think I can get a goo d price
- The guy fitting and setting them up knows what he's doing (and said the same as sherlock, go for them if the price is right)

Ok, I know, that's 3 reasons... what is this, the spanish inquisition?

Any more for any more?

Cheers,

Adam

[Wil_h]

It all comes down to cost and ease of fitment. It seems that there is no advantage to using the split webbers generally, just disadvantage (no more power and more weight and complication).

However, in your case if they are good value and are just a bolt-on mod then I'd go for it. Plus people will get excited when you open the bonnet!!!

Edited by Wil_h, 24 September 2009 - 10:04 AM.

[adamg1380]

It all comes down to cost and ease of fitment. It seems that there is no advantage to using the split webbers generally, just disadvantage (no more power and more weight and complication).

However, in your case if they are good value and are just a bolt-on mod then I'd go for it. Plus people will get excited when you open the bonnet!!!

by the way, I did consider the 1000cc turbo route, I was thinking of a 1275 stroked to 1000cc to get a squarer bore and so that it could use a 1275 based head without any block work. Lack of experience, workshope and equipment has meant sticking to the "standard" 1380 route, maybe one day...

Cheers,

Adam

[Wil_h]

I have lots of 998 turbo ideas, mainly centering around getting rid of the carb and having injection. Short stroke, big bore makes heas choice easier, especially when thinking about more than 5 ports.

Good luck with your project, if you want a friendly championship tha goes to all the 'big' hills then go look at the HSA. www.hillclinbandsprint.co.uk

[Sprocket]

A pair of webers are wasted on a mini

Edit:

What i really meant to say is, A pair of Webers are wasted on a five port engine

[Sherlock]

I've been looking through my archives & I've found the official Abingdon word on split Webers, on the 90 bhp works rally 1275 S they gave an extra 7 bhp & improved torque, compared to twin 1.5" SU's. The reason for them being split was to allow them to be fitted to the group 2 SU type inlet manifold, a single 45 DCOE would have put the car in group 6 because of the change of manifold & technically only having 1 carburettor. So, by splitting the Webers, they could get group 6 performance with a group 2 car. I still say grab them if the price is good, particularly as they are a Longman set up.

[Wil_h]

Very interesting. as with so many modifications with race cars, they are done to get around tight regulations, rather than being the ultimate in performance. But because it's ona race car, it must be the best!!

An example being that some believe 10" wheels to be the best because that's what Migs use, but tyre size is regulated.

[Sherlock]

Not wishing to be too controversial, but I thought virtually everyone believes that 10" wheels are best, not just because Miglias use them, but because the roadholding is so much better.

[adamg1380]

Not wishing to be too controversial, but I thought virtually everyone believes that 10" wheels are best, not just because Miglias use them, but because the roadholding is so much better.

getting a bit off topic now but.. do you mean for road or race?

This seems to work pretty well on 13s: http://www.billricha.../wp/?page_id=10

I've spoken to a few people who've said that once you get rid of the body roll (race cones + anti-roll bars both ends) then larger wheels work fine.

Mine's currently on 12s to clear the brakes, which is possibly the worst of both worlds - not as much tyre choice as either 10s for road class (no 008s) or 13s for sticky stuff. Luckily I think (not sure yet) that my class will movign to MSA list 1B for next year, which means I can use 048s. I might leave it on 12s while I get the engine & box sorted if that happens.

[adamg1380]

A pair of webers are wasted on a mini

Edit:

What i really meant to say is, A pair of Webers are wasted on a five port engine

Well, a full pair would be, but really it's a pair of half-Webers - which could be seen as a terrible waste as you chop off chunks of each carb!

I'm sort of liking the idea a bit now, in a "it's a classic setup" way.

[Sherlock]

Not wishing to be too controversial, but I thought virtually everyone believes that 10" wheels are best, not just because Miglias use them, but because the roadholding is so much better.

getting a bit off topic now but.. do you mean for road or race?

This seems to work pretty well on 13s: http://www.billricha.../wp/?page_id=10

I've spoken to a few people who've said that once you get rid of the body roll (race cones + anti-roll bars both ends) then larger wheels work fine.

Mine's currently on 12s to clear the brakes, which is possibly the worst of both worlds - not as much tyre choice as either 10s for road class (no 008s) or 13s for sticky stuff. Luckily I think (not sure yet) that my class will movign to MSA list 1B for next year, which means I can use 048s. I might leave it on 12s while I get the engine & box sorted if that happens.

I did mean for road or rally use, obviously with enough resources you can set up a racer & virtually design the suspension around whatever wheels you want to use. I fully appreciate the limitations caused by 8.4" brakes. Getting back O/T, my mate Len used to race a Miglia with Longman engine & split webers, he was very happy with them, almost as happy as he was with the 2 championships he won!