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Marks Rans Courier Project
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Date: 9-7-2008
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Number of Hours: 4.00
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Manual Reference:
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Brief Description: Carb heat units
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The later models of the S7 now come with carb-heat systems. Apparently all of the S7-series of planes prior to the S7S did not have carb heat. There is quite a bit of discussion regarding the need (or lack of need!) for carb heat on the Yahoo Rans S7 forum. The general consensus is that Rans added the carb heat feature as part of the S7C certification process, and left it on the S7S and LS models. Several of the guys I trust have removed the carb heat units indicating that they are un-needed. Several other frequent-flyer types report clearly having had carb-ice issues, and clearly advise in favor of keeping the units. I originally decided to pretty much hold to the stock design in building the plane, so after a lot of consideration I am installing the units per the manual.
The carb heat manifold has a butterfly-type valve inside the manifold body. The butterfly has to be fitted to the inside of the manifold. The first one I started to work on was not even close to fitting. I spent several hours fitting the butterfly to the inside of the manifold. This involved installing the brass bushings (press-fit with Loctite648), installing the butterfly shaft, then carefully marking, filing, sanding, trial-fitting, remarking, filing, sanding and re-installing the butterfly until I acheived a close fit.
The photos below show the manifold body with the fitted butterfly installed.
Note: I decided that the manifold looked a little rough and needed to be polished up. I worked on one of the manifolds using the cloth wheel and polishing compound to no avail. I guess whatever alloy the units are made of isn't suitable for polishing.
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