This page is to shed some light on the Tillotson HD carb I am attempting to use on my CorvAir engine.
Shown above is the manifold, carburetor, and heated air intake damper installed on the engine.
Pictures above show the relatively rare (HD11A) factory "pump delete" setup used with external fuel pump and the "pump detete" modification of a pumper carb. Note the old fuel inlet is now the "safety drain" to route any fuel leakage from the top of the engine. I am looking into using this for a cockpit controlled mixture device (leaning) as well.
This shot shows the modified and original bottom plate from a pump equipped Tillotson HD carb.
There are two basic configurations of Tillotson HD carb, what I call the "bombsite" and "emulsion" type.
Note the small "bombsite" booster venturi in the picture on the left, and the "emulsion tube" on the right.
The adjustable main jet is the one with the "T" handle - the other is the idle jet (towards center of 2 pictures)
The "emulsion tube" carb is similar to the Walbro carb shown below.
Note the adjustable main jet needle in the top of the carb.
These carbs are officially known as "regulator" carbs, and are also known as "diaphragm" carbs.
Picture on the left shows the diaphragm. Picture on the left is the regulator mechanism under the diaphragm. Note the needle and seat ass'ly at the bottom and the regulator lever and pivot. The "pump detete" option requires the passage to the right of bottom to be plugged (brass plug shown in the little "ear".