CR: I agree that the purpose of the vaccuum control on carbs that have such is
to progressively open the second barrel as rpm and hence CFM through the carb
is increased. What I meant to say, was that this will cause fuel to move
through the main jets of the secondary barrel sooner to better respond to a
continous, progressive throttle opening, especially in the bottom mid range
when the primary barrel isnt enough anymore and the second barrel starts to
come into play. The DGV doesnt have such a device. Its been so long I dont
even remember every thing that was done, but I also attempted to change the
stroke of the accelerator pump to provide that extra shot of fuel earlier.
That wasnt enough. The car ran fine in balls-out, wide open mode, but was
frustrating in normal driving. It stumbled, or more correctly, hestitated
momentarily, at part throttle openings. It no fun driving an on-off switch. In
the end the modified linkage helped the most, which in effect was to do
mechanically what the vaccuum control does on other carbs . As I said, I think
I would have been better off with the stock SUs. Every engine responds
differently and IMHO the layout of the ports on the MG head work best with two
balanced SU carbs. Cheers, Andy Blackley
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