If the RH exhaust pipe heat riser butterfly valve is removed, the carburetor base still gets indirect heat from the the center cylinders via the center cylinders exhaust valve heat ports and the heat passage under the carburetor in the intake manifold. . With the RH exhaust pipe heat riser valve is removed, it takes the carburetor base slightly longer to warm up and the choke slightly longer to fully open. The choke has a rich (winter) or lean (summer) adjustment which can adjust for the delay. The rich or lean adjustment raises or lowers the pre-load on the bi-metal spring in the carburetor choke mechanism.
After I filled the heat passages in the heads with molten aluminum, the bi-metal spring in the carburetor choke mechanism received no heat at all. The main reason I filled the passages with aluminum was to prevent the exhaust heat from burning the paint off the intake manifold. That is dumb mistake for a car that is sometimes driven on the street in winter. Blocking the heat passages in the heads is used on race cars at the strip in order to cool the carburetor base and the fuel for a denser mixture but it is ineffective for a car that is driven on the street after the engine reaches operating temperature. A cool air carburetor intake is a better idea and is sometimes worth 2 tenths in the quarter mile.
Last edited by MouseFink; 01-14-2013 at 05:53 PM.