The 4160 only has one metering block and for the secondaries it uses a metering plate. This metering plate only allows a certain amount of fuel and the entire plate has to be changed to change fuel flow.
Holley however makes a conversion kit that replaces the metering plate with a metering block. This allows the use of Jets to control the fuel flow to the secondary barrels. This really turns the 4160 carburetor into a 4150 with vacuum secondaries.
I started off by pulling the secondary vacuum control and the electric choke. Then the throttle base, fuel bowls, metering block and metering plate.
That really does not leave much except the body of the carburetor. The only thing really to remove here is the “squirter” and the needle which has to be removed so you can clean it. The same parts went back into the body since replacements were not part of the rebuild kit.
The squirter is the nozzle used by the accelerator pump to squirt fuel directly into the primaries when the gas petal is pressed. This keeps the engine from bogging when there is high demand for fuel.
Next was to remove the gaskets, power valve, and jets from the primary metering block. Then grab the B-12 Chemtool and clean all the parts. Some of the smaller parts I just soaked in the B12 and then cleaned them with a rag, others I had to spray quite a bit.
This was one dirty carburetor, I have no idea what is in the bottom of this float bowl. But the Chemtool cleaned it right up.
Now that everything was cleaned up it was time to reassemble the carburetor. I started by replacing the power valve and jets into the metering block. I selected the 6.5 power valve as the cam I have in the motor shows that I should have around a 12″ vacuum.
A new metering block came with the conversion kit. The only difference between it and the primary block is the new one does not have a spot for a power valve. It also does not have idle screws since it is all controlled via the vacuum control. It came with the gaskets, jets, and longer screws for the float bowl.
The rebuild kit comes with three diaphragms, one 50cc and two 30cc. Since this carburetor has vacuum secondaries only the primary bowl has an accelerator pump. I used the 30cc diaphragm since that was the one in the stock carburetor.
I then dropped in the new float needles and set the float level. It will have to be set once the fuel flows into carburetor.
The only difference after it is all put together is the length of the carburetor. The new metering block adds about 3/4 of an inch.
Now the only thing I need are new fuel intake fixtures. The ones that came with the carburetor were made for AN -6 hoses. The dual feed fuel line I have has standard 5/8″ outlets. I would rather not have to spend the extra $80 to $90 to get a new feed line.