First issue 1950s 4150 Holley carbs

In the late 1950s the Holley 4000 series or “Teapot” needed a redesign.

Holley came out with the 4150 series.

The earliest ones I have seen are from May or June of 1956. These were the first of the modular style Holleys that we know so well.

As seen, we have the basics of the modern Holley 4150 style we know and love.

Primary and secondary bowls, two metering blocks, a baseplate, and accessories.

Like any first issue there are a ton of small details that make these distinct compared to later models. This article is meant to go over some of these. Many of these details are really neat, others, well you can see why they were changed later as they are clunky or a bad design.

Typically these carbs come in a few sizes.

390cfm, 425cfm, and 600cfm.

Shown in this post is a List 1273

Lets start with the baseplate:

As shown the throttle shafts, spring and pump cam are specific. The spring is distinct, the accelerator pump cam is steel.

The pump cam slides over the entire shaft as does the spring. The pump cam screw is specific but it isn’t terribly difficult to find a replacement if needed.

The pump post has a roll pin, so if you need to remove the post you have to also remove the roll pin.

Notice the spring and idle speed screw and how that is mounted differently.

Unlike modern secondary shafts, this one only takes three teflon ribbons.

This baseplate takes two different plates. 103 plates for the primary mount in a normal manner.

The secondary plates are 96s, they install in a different orientation compared to what you may be used to seeing.

With these smaller carbs you will often see both the primary and secondary transfer slot showing. This is normal.

This particular carb came with the incorrect pump lever. Not a big deal, but I will show the differences.

The correct one is oriented differently as shown above.

Either way, you really need to be careful about how the level lines up on the cam as there isn’t always a lot of room with the metal cams. The lever falling off the cam can jam the throttle.

Distinct hardware is often used.

Moving onto the Bowls:

Again these are far different than their modern replacements.

First of note is they take highly specific needles and seats, as well as floats.

I sell rebuild kits for these carbs, my needle and seats are the same as the originals.

The assembly is three pieces:

The first versions of these did not have posts for the bowl gasket to attach to, this makes it fairly difficult to line up.

The earliest of these had a really small post to retain the bowl gasket, typically these are broken. You will also notice the metering block has a spot for this.

Accelerator pump check is pretty nice, it is removable from the bowl.

I typically remove it during a restoration and reseal it during install.

Primary vent lever is actuated by the pump lever.

It is retained in the bowl by a spring and 1/8in e clip.

The carb I was working on had the incorrect pump cover. Any new styles will work fine, this is what the original looked like:

One annoying issue with these bowls is they do not have much reinforcement around the bowl screws, as such the bowls themselves often warp.

Trying to knock them back out with a punch helps. Once decently pressed back you can use a fine file to help flatten the bowl so it seals well.

To prevent warpage issues, make sure to use original style soft bowl screw gaskets. Nylon gaskets will absolutely warp these are there is no give to them. Once these are warped it become difficult to seal at the bowl screws as the screw gasket doesn’t have a flat surface to seal to.

Shown below is the inside of the bowl lacking good reinforcement.

Floats shown below:

The floats have two tabs. One is to set how high the float can go, the other sets how far it can drop.

A nice touch on many of these is that many of the drilled holes have small brass tubes installed that help line up things.

The accelerator pump system does not use a needle, it uses a small ball and weight.

You should not use a needle as there is no proper seat like later models have.

These carbs often have very odd and specific calibrations. You really and truly need a data sheet to make sure these are correct.

In the case shown here, you have really small secondary jets, but large secondary pvcr and an early opening secondary power valve.

You will also notice this carb has a massive idle feed at .035, this is partially restricted with a super small seat for the mixture needle at .045

I personally find these are brilliantly engineered for the original engine, that said they often do not adapt well, making changes often makes them massively worse.

A few other distinct parts that were missing from the carb I have shown:

The needles have a really nice aluminum vent baffle to prevent fuel slosh:

Originally the fast idle cam was steel, this had a more modern plastic cam.

The original seal for the choke rod is two small pieces of brass sheet and felt in between them.

Anyway, best of luck with these, hope this blog helped out in some way.

Thanks for reading this,

Drew