Holley came out with the first modular carburetor, the 4150, back in '57. Today, Holley still makes the 4150-heck it even makes hopped-up versions for everything from drag racing to rock crawling. With times getting tough, a brand-new shiny carb may be out of reach for some enthusiasts, but a decent used carb may not. There always seems to be a guy at the swap meet or a friend of a friend that has one ready to be fixed up.
Case in point: We traded a buddy a set of valve covers for this Holley. He said when it was on his 350 it sputtered a bit off idle and during a heavy foot load of pedal it seemed to run out of gas. A bad filter or something clogging the fuel line was our first thought, until we got the sucker apart. Someone had rebuilt the carb previously and did a mediocre job to say the least.
After calling the Holley tech...
After calling the Holley tech line and giving the guy the serial number of the carb (stamped on the choke tower), he gave me all the part numbers needed for the rebuild kit, electric choke...
There was a ton of old gasket material that wasn't cleaned off between the metering blocks and the main body, most likely creating air leaks. They also forgot to trim off the tip on the rubber umbrella check valve in the fuel bowl, which prevented the float from going all the way down when the fuel got low. The needle and seat assembly could fill the bowls, but not fast enough under heavy acceleration because they couldn't open all the way. This little oversight kept the carb from functioning to its full potential and, in turn, made his car a pig to drive.
Another issue with the carb and a major trend that most Holleys have fallen victim to is the removal of the choke system. Some even had the choke tower machined off completely. Most were ditched as guys tried to squeak out every ounce of power they could for lower quarter-mile times. While gains can be found hacking away chunks of the main body, for many it isn't worth losing the choke unless you're building a drag race-only vehicle. The carb we got was missing all the rods, levers and even the choke blade, but luckily the choke tower was still in place.
...kit and upgraded float...
...kit and upgraded float bowls. Holley offers two levels of rebuild kits; one is a basic rebuild kit that has everything needed for a simple rebuild. The second is a Trick Kit that gives...
Before doing anything we inspected the throttle shafts to see if there was any amount of play in them, which there wasn't, so this one qualifies for a quickie refurb. If you can grab the throttle and wiggle it up and down you will need to buy a new base plate or send it to a professional shop to have bushings put in.
We ordered a rebuild kit, electric choke kit, an upgraded set of glass sight fuel bowls, and all the replacement choke parts from Holley. We also picked up a few cans of carb cleaner and a can of gasket remover from the local parts store to speed up the rebuild process. There are a lot of things to learn about carburetors and how to tune them, which we will go over in another story at a later date; this one will outline the simple steps to bring a carb back from the dead.
 ...you everything the basic...  ...you everything the basic kit comes with, along with a bunch of tuning parts to adjust for different motor and cam selections. The float bowl upgrade contained new center hung float... |  ...bowls and all the gaskets...  ...bowls and all the gaskets needed for the swap. The choke stuff included the shaft, plate, and the electric choke conversion kit. The entire parts list cost us just… |  ...over $180 and a new 650cfm...  ...over $180 and a new 650cfm is $350 so we saved about $170. We decided to spend $87 on a black Ano-Tuff fuel line kit from Earl's to feed the float bowls. |
 The fuel bowls will be the...  The fuel bowls will be the first thing to come off; they are held on with a 5/16 head bolt. The bowls can stick, but fight the urge to pry them off with a screwdriver. A couple of medium-to-light taps with the handle of a screwdriver should be enough to pop them free. As you can see, this carb has the blue gaskets in place already. This is what told us it had been rebuilt. |  Look what we found hiding...  Look what we found hiding beneath the blue gasket-remnants of the original gasket material. This is not acceptable. Holley makes good gaskets, but to think they will give you a perfect seal over this crud is just ludicrous. |  With the bowls off, we moved...  With the bowls off, we moved on to the base plate, which is held on with Phillips head screws. Once you have them out, separate the main body from the base plate and inspect the base around the mounting ears. It's pretty common for these to crack from being over-tightened; luckily, ours was in perfect shape. The basic rebuild kit comes with a few different base gaskets so before you destroy the old one removing it, find the right one and set the others out of the way. This will cut down on confusion and prevent you from inadvertently installing the wrong one. |
 Moving back to the top of...  Moving back to the top of the carb main body, the accelerator pump discharge nozzles are removed with a Phillips. The nozzles should be the same size for the primary and secondary circuits; ours were the factory-installed 28s. Hiding underneath each nozzle is a little needle that can be shaken out by flipping the body over, but be careful. Lose one of these and you are dead in the water until you can get a new one or find the one you lost. The needle prevents fuel from being sucked out of the nozzle when air passes by the venturi. |  Because our carb is missing...  Because our carb is missing the choke assembly, we can move on to tearing down the bowls and metering blocks. If you have a choke assembly, remove the little clip from the linkage rod and remove the three screws holding the assembly on. There is only one power valve on the non-Dominator-style carbs like this one. It is in the primary metering block and requires a 1-inch wrench to get it out. Pull the jets out of the metering blocks and give them a good soaking with the carb cleaner. Keep track of what jets were in what metering block, but if you forget the smaller numbered jets go in the primary metering block. Also compare the old power valve with the new one making sure they have the same numbers stamped on them. Ours had a six and a five stamped on it, letting us know these will open at 6.5 inches-Hg. The rule of thumb is to have a power valve that is marked with half the amount of the engines vacuum at idle and 6.5 is good for most stock small-blocks. |  Most damage that is done to...  Most damage that is done to a carb happens while you are removing the old gaskets. We used gasket remover from Permatex that eats the material and makes it very soft and easy to remove. After a few minutes the old gasket will soften up and easily come off with a plastic scraper. Try not to use a metal scraper as it can scratch the metering blocks and possibly hinder sealing. |