First, is it necessary to block idle circuits in one carb for a dual 94 setup, second, what is the best way to do it? Thanks in advance.
You are dealing with 2 different circuits in the carb's curve...actual idle fuel comes through the lowest hole below throttle plate, off-idle right above idle plate. This one actually runs the cat til enough air is going through to make venturis operate. Both are fed through the idle jet; fuel from here is further metered by the needle valve at idle, but the jet controls total flow for the off idle. Normal procedure secondary carbs would be a blank gasket between lower and main parts of carb or holes in base casting blocked at same level, killing both circuits. On a car with fairly low rpm tip in of secondaries, there might be a tuning point here by plugging only idle (turn in screw) and leaving off-idle open...just a thought. With two carbs engaged at idle, controlling the very small airflow well enough becomes an issue. A typical procedure might be: Remove carb uppers, bolt throttle bodies to manifold. On 94's, life becomes easier if front screw for this is replaced with hex or allen type... Get all 4 throttles fully closeable, actually do that before bolting to manifold... shut throttles, scrutinize edges of blades with good flashlight. Loosen screws holding plates slightly and jiggle and motivate as needed to get light-tight seal, retighten. Install bases and linkage so linkage links with all 4 closed...then you have a chance of getting all 4 adjusted to the very small opening needed for proper idle and can get on with adjusting mix. By the way, changing flathead manifold is very easy...if engine is newly built, assemble with stock manifold and one carb till engine is running properly and ignition is fully flogged. Then you only have to mess with the new variables as you install duals on an engine with known idle and running behavior.
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