Wow! the British guy really seems like the DD 32/26 and doesn't think much of the DCOE. However, if I have got what he says correct, he's the only one who says that well set up CD 150's are as good as the Webers (sometimes better??). Off the topic, Rootes Racer pointed out that I misinterpreted what he said and I confess - it was Eleven and not him that talked about the the DD flow path. My mistake. The concensus seems to be that either Weber set up will give improvement and so the question becomes is the extra money for the DCOE's and the fiddling to get them to fit worth it. Anyone's opinion and/or experience on that point is welcome.
Actually the guy started off touting the benefits of the 28/36 DCD, an even meeker variant.
When you talk about all these DGV, DCD and DFV variants, the numbers on the front (throttle plate diameter) only tell part of the story, the other and often more relevant is the effective diameter of the "cast in" ventruri (henceforth I will call a "choke").
The 38/32 and 28/36 units are for small displacement, high mileage cars and have very small chokes for strong jet signal.
Small chokes also mean high flow restriction, which is best described as anti-horsepower.
The main reason the guys carb philosophy is seriously flawed is in describing
the CFM flows of the carbs. DCOEs have variable CFMs in that the choke diameter determines the restrictivity of the carb. No 2 bbl DGV carb with
even 32/36 throttles and their inbuilt 24 and 27mm chokes can outflow a 40mm DCOE with "smallish" 27mm chokes.
If we say the 32/36 has 215CFM flow potential (we'll ignore that we dont know the pressure drop spec), a single 40mm DCOE with 27mm chokes will flow around 250CFM all things the same.
Since that one DCOE is feeding TWO cylinders at about 125CFM each, the net flow potential for all 4 cylinders is 500CFM.
A 2bbl carb flowing into a single plenum 4 cyl engine becomes multiplexed flow. All 4 induction pulses flow through the sum of both barrel flow paths.
This makes the jetting signal stronger for the CFM it produces, but at the expense of flow resistivity. The flow through a DCOE equipped engine becomes single carburettor per cylinder (provided there is no plenum) and the flow is simplex where the single flow pulse for that cylinder creates the depression for that cyls main jet. The resultant sum flow of all cylinders in CFM per inch of pressure drop becomes larger ( a sign of flow efficiency).
We could talk about the added advantage of having a single runner straight in the head flowpath, but I think that goes without saying.
As for the CD150s, they were a good carb for the time. The theory of operation was sound.
New and unworn units had good fuel linearity due to the app specific tapered
needles.
Throttle response was better than most conventional carbs since the sudden throttle opening resulted in a large depression and excellent main jet signal.
The downside for the CD150 is that it has a rather high pressure drop as a
function of flow and again you are multiplexing multiple induction pulses through a common metering element.
As for experience with DCOEs, I have had them on my car for over 15 years.
I actually have 3 different sets, 1 pair of spanish weber 40DCOE151s, a pair of Japanese solex/mikuni PHH40s and a pair of japanese OER PHH44s.
The best carbs by far are the OERs, they offer a level of quality that weber NEVER had, used weber main and idle jets and other critical tuning parts.
They also feature externally adjustable float level adjustment and the best
emulsion system of any carburettor I have ever worked with.
I should warn you that going weber DCOE is not simple, cheap or easy.
No two engines seem to jet up the same even with similar internals, and unless you are very, very experienced or pay someone who is, you can spend years trying to get rid of that last little annoying calibration compromise.
DCOEs are the most tunable carb option for almost any application, the degrees of tuning freedom means you will spend a lot of $$$ on jets, chokes and other hard parts.
To tune them you will need a good flowmeter. I also recommend a wideband O2 sensor with a display of some sort.
If any of this sounds like it is out of your league, it probably is.
Many folks have gotten the webers bug and went down the path only to reverse course in favor of simpler albeit lesser performance carburetion.
If you are independently wealthy, particularly stubborn or absolutely uncompromising, then DCOE webers may enrich your life.
