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.
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.
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.