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Discussion in 'Vintage (thru 365 GTC4)' started by Lowell, Apr 6, 2018.
Again, what diaphragm? Where is it? What does it do?
Over and now out forever.
The diaphragm in the later Webers serves as the accelerator pump. Though, in the eralier Webers, like Lowell's, I'm pretty sure the job is done by a brass piston.
Apologies. My mistake.
I shift by the sound; I think if Lowell’s engine (and his car is beautifully maintained, btw) sounds good, it probably is good. These cars are remarkably robust in my limited experience. I wouldn’t and don’t hesitate to drive near the redline in mine.
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Late 330 GT S2s had Weber 40 DFI/2 carbs, not the DCZ/6 as in Lowell's car. I wonder if the DFI/2 used the diaphragm? The Weber 40 DFI 5 and 6 do. Service kit for DFI 2, 5 and 6 below.
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My above post should read Some late 330 GT S2s had Weber 40 DFI/2 carbs. I don't know if all the later ones had 40 DFI/2s. Damn 10 minute edit limit.
DFI 2 carbs use the diaphragm. It can definitely dry out and the early versions were subject to deterioration from ethanol.
An accelerator pump should not affect the safety of the engine at full revs.
BMW: Your statement is not correct. On many Weber carburetors, the accelerator pump jets also function as high speed fuel enrichment feeds.
There are a number of early S1 330 GTs identified on Kerry's site as having 40 DFI (not DFI/2) carbs which I believe may also have the diaphragm?
My bad. My experience is with Del'orto motorcycle carbs which simply add a charge for acceleration. I made an assumption.
Steve: The DFI model used on the Tipo 209 motor was a DFI 2. I assume some owners failed to include the suffix in describing their carburetors. As to when the DFI replaced the DCZ, that gets murky. I would say that roughly chassis number 8400 starts the DFI units on 330 engines (but the changeover was not "crisp" with DCZ's still appearing from time to time). I would suspect earlier cars that now have DFI carbs have had the original DCZ units replaced at some time in the past. The DFI was a more "modern" carburetor and was also less expensive for Weber to produce. It does not have replaceable chokes, and the diaphragm accelerator pumps provide a "quicker" squirt than the piston design.
My 330GT S/N 8855 has (I am pretty sure) 40 DCZ/6 carbs.
Bob Wallace rebuilt my 330 GT engine in the late 70s. (#9693) . I have 161000 KM on it now, and keep it tuned and valves adjusted, oil changed etc, and drive it regularly. I have hit over 6000 RPM and it makes great noise but never went past that.... why take the risk!. I am pretty sure the engines of GT and GTC are basically the same engine internally. I have 40 DFI2 carbs, and pretty sure they are original to car as the main long term owner kept records even when he changed spark plugs, for example, before or after a long trip, or after racing at the Virginia City Hill Climb and coming in 2nd. And yes 6600 RPM is the correct Max