6 replies to this topic

[Sputnik]

Hi all,

I have just removed my 40 weber to replace it with a 45. I have measured the inside diameter of the manifold and on the carb side it is 44.5 mm and then tapers down to 36mm on the head side.

Will this manifold work for a 45 weber, or do you have to buy a 45 specific manifold ? I see that minispares advertise theirs as 45's

The head is modified as I use the car for racing and the inlet ports on the head is more than 36mm in diameter.

Advice would be appreciated, as I do not want to purchase a 45 weber manifold, Import it and then the diameters might be the same.

[KernowCooper]

44.5mm will be bigger than a 45 DCOE as a 45weber will not take a full 45mm choke and I dont see a problem with your fitment

From memory without getting the books out I seem to remember a 40 will take 24-36mm chokes and a 45 28-40mm chokes. I know some have had a 40 bored out to take 38mm chokes but the above are the normal sizes from memory

Edited by KernowCooper, 19 January 2013 - 09:32 PM.

[bmcecosse]

You don't want any 'steps' in the flow. You should simply blend the manifold end to match the size there - and also blend the carb end to match the carb exit. Although a 45 DCOE takes smaller chokes - the throttle plate will still be 45 mm - so make the manifold match that. It won't take too long to do a good job!

[Sputnik]

Hi, it seems that one of my reply's disappeared :-(

Thanks for the feedback. It was my intension to match the sizes on the manifold and carb and head as much as possible respectively.

At least I do not have to purchase another manifold. The dum question now is : should the manifold taper to a smaller size inlet at the head. Should it not be better for the carb, manifold and head to be at 45mm right through ??

[The Principal]

Maniflow supply different sized inlet manifolds for webers suitable for worked heads or standard with or without servo take-off's

http://www.maniflow....54&product=1105

[KernowCooper]

Hi, it seems that one of my reply's disappeared :-(

Thanks for the feedback. It was my intension to match the sizes on the manifold and carb and head as much as possible respectively.

At least I do not have to purchase another manifold. The dum question now is : should the manifold taper to a smaller size inlet at the head. Should it not be better for the carb, manifold and head to be at 45mm right through ??

Yes as said above by bmcecosse above match the Carb 45mm plate to the inlet which you have said is 44.5mm so a small amount of work to open it to 45mm and take out and steps and your sorted.

As for it not being 45mm right through question in a ideal world with 45mm ports and 45mm valves, but a 45DCOE will have smaller chokes i.e 40mm max so its smaller on the intake to the choke anyway than the Carb mounting plate and your modified manifold entry. 45 mm all the way into a minis combustion chamber I'd imagine would give poor gas speed and terrible low speed running much like putting a 50DCOE on a Mini Cooper 998.

Edited by KernowCooper, 20 January 2013 - 02:18 PM.

[Sputnik]

Hi dalligaf,

I use the car for racing only and in South Africa, no chance of such temperatures as yet !

Thanks for the feedback in any case. I have also realized how dum my question was with respect to the 45mm right trought, as the valves are only 36mm !!