Holley 4150 Carb Rebuild - Super Chevy Magazine

Holley 4150 Carb Rebuild Choke Rod Slips

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 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...

After calling the Holley tech line and giving the guy the serial number of the carb (stamp

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 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...

...kit and upgraded float bowls. Holley offers two levels of rebuild kits; one is a basic

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 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...
...you everything the basic kit comes with, along with a bunch of tuning parts to adjust f
...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…
...bowls and all the gaskets needed for the swap. The choke stuff included the shaft, plat
...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.
...over $180 and a new 650cfm is $350 so we saved about $170. We decided to spend $87 on a

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.
The fuel bowls will be the first thing to come off; they are held on with a 5/16 head bolt
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.
Look what we found hiding beneath the blue gasket-remnants of the original gasket material
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.
With the bowls off, we moved on to the base plate, which is held on with Phillips head scr

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.
Moving back to the top of the carb main body, the accelerator pump discharge nozzles are r
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.
Because our carb is missing the choke assembly, we can move on to tearing down the bowls a
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.
Most damage that is done to a carb happens while you are removing the old gaskets. We used

After we got all the gasket material cleaned off, we noticed this little imperfection on the main body that was caused by someone aggressively prying off the metering block. ...
After we got all the gasket material cleaned off, we noticed this little imperfection on t
...This is why we recommend lightly tapping on the bowls to break the seal. To cure this imperfection we took a fine file and carefully ran it across the main body until the nick was gone.
...This is why we recommend lightly tapping on the bowls to break the seal. To cure this i
After all the filing and gasket scraping was complete, we cleaned all the parts down with some carb and choke cleaner and a few brushes. This will remove any varnish or crud inside the passages, which will hinder performance.
After all the filing and gasket scraping was complete, we cleaned all the parts down with

Since we matched up the gasket beforehand, it was easy to just drop in the new base gasket and install the screws. It's a good idea to add a small dab of thread locker to these screws so they have no chance of backing out and dropping down the intake.
Since we matched up the gasket beforehand, it was easy to just drop in the new base gasket
With the base plate on, the unit was flipped over to reassemble the discharge nozzles. The needle must be dropped in the nozzle passage point down before the squirters and new gaskets from the kit can be tightened up.
With the base plate on, the unit was flipped over to reassemble the discharge nozzles. The
We set the main body aside and proceeded to the metering plates and fuel bowls. Before you remove the idle mixture screws, crank them in and count the turns it takes to bottom them out. Ours took two full turns; if you forget the baseline is 1.5 turns out. Make sure to dig out the little cork ring that will usually stay in the metering block. A little more cleaner in the idle screw hole and then compressed air to blow out the passage will be good enough.
We set the main body aside and proceeded to the metering plates and fuel bowls. Before you

The new power valve goes in just like the old one came out. Holding it upside down will help keep the gasket positioned correctly. We also reinstalled the jets right before this picture. Whatever you do, don't forget to put those back in.
The new power valve goes in just like the old one came out. Holding it upside down will he
The new cork ring should be installed into the metering plate first then thread in the screw until it bottoms out and then back it out to match the initial setting, two turns in our case.
The new cork ring should be installed into the metering plate first then thread in the scr
We're just about ready to install the upgraded fuel bowls, but some of the old parts need to be transferred over first. Starting with the accelerator pump, the new rubber umbrella from the kit is pulled through the hole. Once the umbrella was in, the pump went back together just like you see it on the table: spring, diaphragm, and then the housing. Make sure to cut off most of the excess of the umbrella so it doesn't contact the float. This was one of the problems our carb had before. The umbrella was holding the float up and kept the needle from opening all the way, basically starving this bowl.
We're just about ready to install the upgraded fuel bowls, but some of the old parts need

With the pump out of the way, we removed the two flathead screws holding the float in place and transferred it to the new float bowl with the same hardware.
With the pump out of the way, we removed the two flathead screws holding the float in plac
Then we installed the new needle and seat assembly from the kit and set it to the proper level with this gauge. If you don't have a gauge, just invert the fuel bowl and turn the adjusting nut until the float surface lies parallel to the fuel bowl casting surface underneath. That should get you close enough to start the car and adjust it properly.
Then we installed the new needle and seat assembly from the kit and set it to the proper l
The metering blocks have locating pins on them to help keep the gasket in place as you install the metering block. With the metering plate on, we install the bowl with the new gasket and tightened the bolts down. One thing that might pose a problem is the throttle linkage that pushes on the accelerator pump arm. Make sure you flip the linkage up on top of the arm before you slide in the bolts.
The metering blocks have locating pins on them to help keep the gasket in place as you ins

The first step in resurrecting the choke assembly is the main shaft. It is inserted though the choke tower, with the tab pointed to the back of the carb.
The first step in resurrecting the choke assembly is the main shaft. It is inserted though
The new plate has a few dimples in it that will lock it into place inside the slit cut in the shaft. A few light taps with a hammer will snap it into position.
The new plate has a few dimples in it that will lock it into place inside the slit cut in
Per the provided instructions, we installed the fast idle lever. The lever consists of two little pieces and a spring. While they will only go together one way, its still kind of a puzzle so really look at the diagram provided with the instructions.
Per the provided instructions, we installed the fast idle lever. The lever consists of two

The choke rod slips through a hole in the main body and connects to the choke lever. Make sure to orientate the rod so the bends point out away from the main body.
The choke rod slips through a hole in the main body and connects to the choke lever. Make
There are two counter-bored holes in the main body that might be drilled through. An easy way to check is blowing a little air in the hole. This carb had sealed holes, but if air had exited from the bottom of the carburetor the hole would need to be plugged with a little lead ball provided in the kit.
There are two counter-bored holes in the main body that might be drilled through. An easy
To make things a little easier, we hooked up the choke rod and installed the little retaining clip before securing the choke housing to the main body with the provided screws. Now is the time for a quick check to see if the choke will operate without binding. We rotated the metal tab protruding from the choke housing and sure enough the choke plate opened and closed.
To make things a little easier, we hooked up the choke rod and installed the little retain

Under the black choke cap is where most of the action will take place. The bi-metal spring will engage the choke when no electricity is flowing through it (cold). When you hit the key, 12-volts starts heating the spring and opening the choke plate. It's important to note that when installing the choke cap, be sure the bi-metal pick-up lever (in the housing) fits into the loop on the bi-metal spring. We checked this by turning the choke cap in both directions. The choke plate opened when rotated clockwise and closed when rotated counter clockwise.
Under the black choke cap is where most of the action will take place. The bi-metal spring
To finish off the choke, we secured the retaining ring in place with the provided screws, slipped on the wiring, and hooked up the vacuum hose. The ground wire hooked right to the main body and the red wire will need to be connected to a keyed and fused 12-volt source. The vacuum hose needs to draw from manifold vacuum to keep the bi-metal spring from overheating.
To finish off the choke, we secured the retaining ring in place with the provided screws,
Since we didn't have a fuel line kit for the carb, we picked up a new Earl's unit from Holley. It's from the Ano-Tuff line and features a tough black finish with a -8 AN fitting on the end. After slipping on the little gaskets the line can be threaded directly into the fuel bowls. Now we have a freshly rebuilt carb that has modern touches like an electric choke for better cold weather start up and glass sites for safe fuel level adjustments all for less than buying a new carb.
Since we didn't have a fuel line kit for the carb, we picked up a new Earl's unit from Hol