Carb Question

[tbdean]

Another question fom the IE5.5-less Eric Bauer:

_ I've seen quite a few DCOE Webers carbs for sale and although they can sometimes share the same diameter (ie 40mm, 45mm, etc), there's a second number that rarely matches. ie in the name: 40mm DCOE 18 for example what does the 18 stand for?

_ Here I am looking at some detailed pics of the Fairlady 432 with its S20 engine and triple Webers. Now of course we know that the S20 cylinder head is a cross-flow where our stock L24 ones obviously aren't. What I was wondering about is why on the S20 the carburetors are bolted directly to the cylinder head? None of the triple carb setups for US 240/260/280 that I have seen ever come without a manifold (be it Cannon or otherwise). So what's the story there? Is it simply because the S20 has a crossflow head that they can get away with ultra short runners (ie carb attached to head) or is there another reason I don't understand?

Doesn't it make sense that the longer the intake runner the higher the velocity of the air/fuel mixture entering the combustion chamber and thus the more punch??

Someone enlighten me please.

-e

[2ManyZs]

Well, I can answer the first part of the question right from my Weber book.

The prefix numbers always indicate the size of the throttle plate.

The letters refer to the general type of carb (downdraft, double throat, sidedraft, although the I in IDA means inverted and they aren't inverted just downdraft).

The suffix (last) set of numbers are the variation of the type or family of carbs.

The book also states the Weber carburetor nomenclature is chaos!! Just as an example the book states there are 10 different variations of the 45 DCOE9.

I am just guessing but I would think the reason for the cross-flow head having the carbs mounted like that would be because of the length of the intake runners inside the head. To tell the truth I never really thought about it, so it's quite possible I don't know what I'm talking about.