Re: 45 DCOEs vs. 40 DCOEs on built 2 Liter

[Les Singh <Les.Singh@domain.elided>]

If you're tweaking the engine towards performance you will probably go with
larger venturis, 37 mm minimum, up to 40 mm max. Fact: there is no way you
can go this large with 40 mm carbs, so apart from anything else you won't
want to limit your options. I know there are formulae that give 37 mm as
the optimum venturi size but the grunt at top end from 40 mm venturis on
45DCOEs is something that you won't want to forgo.As a matter of interest,
the GTA 1300 Jr runs 40 mm venturis, so that blows the "too large"
criticisms out the window when we're talking performance.
 
I have run 40 mm DHLAs and DCOEs, and 45 mm DHLAs and DCOEs on my car with
various cams. I have all of these carbs sitting around and swap them from
time to time to make comparisons - takes about 30 mins for the swap.  At
the moment, in the interests of economy and daily driving, 40DCOEs are on
there with small venturis and,  they work very well on the road, but the
big top end horsepower just isn't there.

Les in Wellington, New Zealand
Green GTV

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