[Tom Vaught]

Holley Model 4150 carbs vs Model 4160 Carbs and their Fuel Bowls.

Part 1

People get confused on the differences between a 4150 carb and a 4160 carb (assuming that the 4150 carb means "Double Pumper" and 4160 carb means "Vacuum Secondary" carb).

Holley has built (for many years) BOTH carb types. A 4150 style carb can be a "Double Pumper" carb but also can be an early 3310 780 cfm Vacuum Secondary carb with a Secondary Metering Block.

If the carb has TWO Metering Blocks then it is a 4150 style carb.

If the carb has ONE Metering Block and ONE Metering Plate (on the Secondary Side of the carb) then it is a 4160 style carb.

Part 2
Most 4150 style carbs also came with what people call today "Race Bowls". The correct term is "Cathedral" Bowls (see attached pic below).
But Holley Engineers call the "Race Bowl" a "Center Hung Float" Bowl. That is more correct.
You can also have a "Center Hung Float" Bowl that looks like a fuel bowl with a long nose on it.
That Fuel Bowl is many times called a "Cathedral"/ "Le Mans" Fuel Bowl as they were used on some race cars in the 60s with Holley carbs.

One Way to keep track:
If the float hinges in the center of the bowl it is a "Cathedral" Bowl.
If the Float hinges on the side of the bowl it is called a "Side Hung" Fuel Bowl.

On the older carburetors (be it Cathedral or Side Hung Bowl), the fuel level hole (with the brass screw sealing it up) was lower on the Secondary Fuel Bowl because the carb sat on the intake at a slight angle. Front of carb slightly higher vs the rear of the carb because the manifold mounting surface was slightly different. Most know that the back of the engine is lower vs the front of the engine.
Same deal for the intake manifold. So the fuel level port in the bowl was different too.

Double Pumper Carbs tend to have the Cathedral bowls with both ports close to being the same.
You need to actually look to see which one has the lower hole (and some do). That Fuel Bowl goes on the back of the carb.

Dominator Bowls with Fuel Inlet threads on both sides of the Cathedral Bowl have a fuel fitting on one side and a fuel fitting PLUG on the other side. So you can get messed up on the fuel level setting. The fuel "Sight" Hole is the same.

I personally set the float (With the bowl upside down) so that the Top of the float (now on the bottom) is barely covering a portion of the Float Hanger Screws. Never had an issue with floats and fuel level being off.

Dominator Bowl Fuel Fittings are designed for 3/8" steel fuel lines. Older Fuel Fittings were 5/16" steel fuel lines. Both will interchange in the fuel bowl and on a street car (not a Race Car) the 5/16" fittings work fine. Race Car 3/8" fittings and lines are better.

Historically Accelerator Pumps on the Fuel Bowls were originally 30cc (per 10 strokes).
Double Pumpers years later got a 30cc pump on the front bowl and a 50cc pump on the rear bowl.
Dominators get a 50cc pump on both ends.
Sometimes on a street/Tight Converter car swapping pumps and hardware helps with the 60 ft times.

For many years Fuel Bowls used Brass Floats. They were installed in both Race Bowls and in Side Hung Bowls.
They worked very well and rarely had a leakage issue.

Later a Phenolic Float was sometimes added the the rear bowl vs a brass float. So it can be correct to have both types of Floats.

Finally, If you have a Blow Thru Boosted carb, the extra pressure in the fuel bowl can crush the Brass fuel float. So guys put the Phenolic Float on both ends of the carb and the crushed float issues disappeared.

All that being said, the Phenolic Float floats could have other issues with some of the gasoline/alcohol blends out there,
so Phenolic Floats are not perfect solutions either.

So that wraps up my post for the day. (Sorry the second image today does not want to get any bigger when you try to select it).

Tom V.