mk1-forum.net

Some one asked to see a close up of these so here they are
Not showing off honest

Didn't know that the works cars used split webers. when was this?

Timo wanted to use Webbers in 67 so had them weld extensions directly on to the carbs, this way it was still classed as one part, and could be bolted directly to the 576 manifold, also meant no bulkhead mods were required.

They look great Nick. Have you done them ?

whistler wrote: ↑Mon Mar 01, 2021 4:51 pm Didn't know that the works cars used split webers. when was this?

After the 1967 disappointment they nearly caused another fiasco for the Minis:
https://books.google.de/books?id=ZwUUDg ... er&f=false

spoon.450 wrote: ↑Mon Mar 01, 2021 6:41 pm They look great Nick. Have you done them ?

Build by Rod at Southam

A couple of sets of original one,s that have had a life

Nick W wrote: ↑Mon Mar 01, 2021 6:58 pm

spoon.450 wrote: ↑Mon Mar 01, 2021 6:41 pm They look great Nick. Have you done them ?

Build by Rod at Southam

Lovely work.

Can anyone explain why BMC competition Department used split Weber’s?
Why not just use one weber DCOE carb, if one say 40 will not pass enough air, use a 45 or even a 48DCOE? Were the two chokes spaced too far apart? If there was space problems what about an IDA (downdraft) Weber
Or for that matter why not stick with SUs, standard was a 1 1/2”, could go to twin 1 3/4” or even 2” SUs
I look forward to someone advising why they did this.

Homologation.
Appendix J for Group 2 required the standard inlet manifold, both before and after the changes for 1.1.66. (That then changed later in the 70s, making the inlet free). It also required no bodywork modifications, illegal under Group 2 which a single 45 on its long manifold did.
It also required that carbs had to fit it without an "intermediate device". Splits with an attachment welded on were claimed (successfully) by BMC Comps to be "prototype" carbs, leading to the 68 Monte scandal. The FIA regs had intended that only commercially available carbs could be used but didn't specify that adequately. Splits were seen by Timo Makinen on a Finnish rally and brought to Abingdon by him.
They did try 1and3/4 inch SUs.
The single 45 was used in Group 6, where virtually anything was allowed but no ERC rallies ran a Group 6 category before 1967. The FIA got heavy handed in 68 and the RAC Rally was stopped from running a Group 6 category in the main rally and had to run a separate parallel rally for Gp5/6.

Thanks for the Peter Browning link - great read.
Do we know what webers the splits were based on?
DCOE13's or 9's, or something totally different.

My investigations concerning "13" and "9" have shown that there is virtually no difference to them. The stroke of the accelerator pump is identical with 18 mm and the progression holes are absolutely at the same spot on both of them. Apart from this, on a comp engine you really do not need the progression phase. Enough petrol is squirted into the inlet channel by the stroke of the accelerator pump when you come out of a corner. The progression makes only sense with nearly closed throttle, then the petrol gets through the progression holes into the channels. As soon as you open the throttle the acc pump takes over.

Check out Mr Vizard's book on Mini Mods and you will see some of the details behind using split Webers and improved fuel distribution
Splits allow each choke of one Weber to be aligned with two cylinder head inlets on A series. Also a good photo of the Longman set up with the sliced Weber.

A well set up works spec 1275 s engine with a 649 cam will pull cleanly from 1000rpm with split webers .
Not something that H4,s will do

I will agree that splits pull from 1000 rpm with 649, had SU H4s before, on the shelf gathering dust and not going back on

What manifolds are available for the splits?
I am after something that does not need firewall mods, preferably in alloy.
Not concerned about air filters, but short stacks would be nice.
Current ones are a bit long for my application.