Symptoms of a fuel mixture that is too rich?

This is the transom after an hours worth of work.....



That amount of buildup seems to be excessive to me. I'm wondering if the fuel is too rich?

What should I start checking?

Yes, a grey/black film on the back can indicate a rich mixture. When my throttle body injection was failing, the back of my '94 was a nasty black mess. The mixture was very rich at idle.

From the "Carb Detective"

Problem: Engine is running rich throughout the rpm band.

Solution #1: You may have the improper size (cfm) carburetor for your application. The carb’s cfm is directly related to your engine’s cubic inches and maximum rpm. Use a Carburetor Calculator to confirm the proper carburetor size for your application.

Solution #2: Although your carb’s floats are pre-adjusted from the factory, they often come out of adjustment during shipping. Check the float level and adjust to the manufacturer’s specifications. If the floats are too high, the carburetor will run rich.

Solution #3: If you’re running an aftermarket fuel pump, make sure the fuel pressure isn’t set too high. As rule of thumb, set your fuel pressure to these ranges based on the carburetor brand: 5-7 psi for Holley, Quick Fuel, AED, Willy’s, or Summit Racing; or 4-5 psi for Edelbrock or Jet.

Solution #4: If you have a carburetor with an electric choke, check and adjust the choke flap to make sure it is opening completely. If it is not opening all the way, there will be an airflow restriction that may cause your engine to run rich.

Solution #5: Evaluate your air cleaner. Dirty air cleaners will restrict airflow and cause a rich condition. The same goes for small air cleaners—install a larger, less restrictive air cleaner if necessary.

Solution #6: If none of the above solutions fix the problems, you’ll need to check for other mechanical issues outside of the carburetor, including worn valve guides, improper spark plugs heat range, or bad valve seals.

Problem: Engine is running rich only at idle.

Solution #1: Try adjusting the mixture screws using a vacuum manifold vacuum gauge.

Solution #2: If you’re running a larger camshaft, engine vacuum will get very low and make the power valve open too early. Swap out the power valve to the correct one for the amount of engine vacuum being produced.

JQ