Can you explain
the dual metering blocks & center hung bowls, Is that a good thing or bad?
I am not a tec, and would like to know more about what you are talking about
If you have the time.
Holley makes two series of carbs that look very similar;
* 4160 which has a metering block on the primary and a metering plate on the secondary. Most of these also have side hung floats and a single fuel feed but some have the center hung floats such as the #3310 750cfm. I believe all 4160's are vacuum secondary carbs
* 4150 which has metering blocks on the primary and secondary. Most all of these have center hung floats with the dual feed for the fuel. They can be either vacuum secondary or mechanical secondary.
The 4160 came into being to create a less costly carb. The metering plate on the secondary side is cheaper than a metering block at the expense of not being as easily adjustable, there are no screw in jets, the whole plate has to be swapped and there are not as many choices. The aftermarket has metering plates that accept screw in jets to solve the problem.
The center hung float came into being to better control the flew level in the bowls on road race cars. Lateral G's can hold a side hung float open allowing the carb to flood. This set up is more costly and that is why the 4160's typically don't have them.
Holley sells kits that will allow you to swap side hung floats to center hung, and swap from a secondary metering plate to a metering block.
Holley sells 4150 series race oriented carbs that get rid of the choke provisions and add in replaceable air bleeds for more adjustability. The top of the line carbs replace cast metering blocks and base plates with billet aluminum that are more precisely made with even more adjustability with the added durability of billet over cast.
For a slant 6 that is primarily for street use there is no real reason pay for the extra bells and whistle. A standard 4160 series 390cfm carb with a secondary metering plate and side hung floats is more than adequate. The $8 quick change vacuum secondary cover is a worthwhile addition to make swapping springs on the car a breeze.
