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    • #57001

      Ok, Here’s a mystery to ponder, I’m out of ideas.

      I’m trying to get a recently rebuild original Autolite 2100 on my 260 Mk1 to idle down. Currently the engine won’t come down from around 1700-1800 rpm with the throttles shut tight. The engine runs perfectly otherwise. Here is what I checked;

      Cold idle cam is off, so it’s not on the fast idle.

      Throttles are completely closed, holding the carb up to the light and looking through the butterflies shows only the tinest sliver of light around the rim of the throttles. The throttle shaft is bushed and has no leaks.

      Engine is in time.

      Good gaskets under the carb and spacer plate to manifold.

      Disconnected the booster vacuum hose and PVC hose to isolate. Also disconnected and plugged to test the distributor vacuum line.

      While running, sprayed carb cleaner on all the junctions, manifold runners, etc. Engine did not change tone, nor was any cleaner pulled in.

      Float level is dead on.

      No evidence of fuel leakage looking into the carb throat will running.

      I can stop the engine by closing the choke plate completely.

      The carb flange to the spacer is flat when checked with a straight edge.

      After running, if I remove the carb I find the gasket a little wetter than I expect. Especially under the powervalve side. I replaced the power valve and gaskets to make sure. The gasket is correct for the power valve.

      Clearly I have some vacuum or fuel leak I have not isolated.

      Anyone have any ideas? Next step is to take it the local carb shop and have them run it on the their carb bench/analyzer to see what it says.

    • #62129

      Wow! Seems everyone is stumped?

      The solution, after reading the shop manual was obvious. The powervalve cover was warped and letting (a lot) of air leak in. A new cover, burnished on a piece of flat glass completely solved the issue.

      The manual has a great, but archaic way of testing the powervalve system.

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