Join Date: Nov 2000
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Re: motorcraft 2100 on 258
As for the lines, you need to determine what source they are currently hooked up to. There are two types of vacuum source, ported and manifold vacuum. Essentially, manifold vacuum is highest at idle, and lowest at open throttle. Ported vacuum is taken from a port above the throttle plates, so it is non-existant at closed throttle (idle) and highest when you just start to open the throttle plates far enough to expose the ports.
As a first step, use a vacuum gauge and determine the source of vacuum these lines are currently hooked up to on the carter bbd. Label them so you can hook them up correctly on the Motorcraft. The Motorcraft carbs I've seen were from 304 AMC's and had ported vacuum from two fittings on the front, so you should be able to restore all functions. The manifold vacuum lines are probably attached to the manifold itself, and can remain in place. Be sure to use a vacuum gauge to verify the source and replacement of any lines that went to the old carb and go on to the new one.
The 2 bbl adapter is called a large two barrel to small two barrel adapter. It does fit the Holley's 2bbls as well on the larger bolt patter. I would suggest using a fuel proof sealant to attach the adapter to your manifold, and replace the slotted screws that come with the adapter with allen head screws.
Good luck with the conversion. If the carb is in good shape, you should be very happy with the results.