Differences between Holley Model S 2 Screw Carbs? What do they mean?

[Benji]

evening all.

Seems I have 2 Holley Model S 2 screw carbs. At first I thought they were identical, but now I see some differences. In the bowl, choke and throttle levers, and the 2 screw cover plate. The bowls have a different shape. The cover is thicker on one than the other, and there are differences in the castings of the throttle and choke levers.

I went to Rhoddas book and there are two Model S carbs in his book, one with a round bottom bowl, and one with a flat bottom. He only mentions that the flat bottom may be a replacement? Seems I have the same two carbs in his book.

But what do the differences mean? Is one earlier than the other?

[Benji]

Last few pics

[RajoRacer]

I believe the 2 screw was on a '12 & the 3 screw soon after.

[Dan Hatch]

Are both sets of arms brass? One looks to be iron. If so which is cheaper? Cheaper = later. Remember Ford was not looking to make car better, they wanted cheaper. Just like today.
You need to get Bruce’s book and look up carbs. I think he has a little more detail.

[RajoRacer]

My apologies - I didn't follow the entire thread - only my first cup of Joe !

[TXGOAT2]

Brass became expensive due to heavy use of brass in WWI munitions.

[Benji]

Everything is brass, and besides, these are 1913 year carbs, so predate Americas involvement in World War One by almost 4 years.

I checked Bruce's book to no avail, and went through the others along with Rodda.. So Im completely at a loss as to why there are these differences in the carbs.

Looking closer at Roddas pictures, it seems my carbs have the same differences in the arms (of course bowl) that his has. I cant tell if the 2 screw plate is thicker or thinner than the other.

Pic 14 has the flat bottom bowl, pic 13 is the rounded bottom.

[Wayne Sheldon]

I "think" your flat bottom bowl has been replaced. Carter carburetors of the 1920s some General motors cars including Chevrolet, as well as several other manufacturers used the Carter carburetors in several sizes. They had a squarish bowl that looked just like that! I have used their floats and bowls a few times resurrecting odd early carburetors.

Other differences were likely production runs and casting variations.

One of your choke levers looks like a later Holley G maybe?

[Benji]

Ya know, I've been wondering about that choke lever being a replacement. And I was surmising the same thing you are, as being from a Holley G. I just hadn't checked today and wasn't going to say much until I did. But, I think it's a possibility since that carb has a new needle and looks reworked.

I "think" your flat bottom bowl has been replaced. Carter carburetors of the 1920s some General motors cars including Chevrolet, as well as several other manufacturers used the Carter carburetors in several sizes. They had a squarish bowl that looked just like that! I have used their floats and bowls a few times resurrecting odd early carburetors.

Other differences were likely production runs and casting variations.

One of your chole levers looks like a later Holley G maybe?

[Corey Walker]

There were 2 styles of choke arms used on the S, one resembling the G arm but without the reinforcement rib cast into the bottom. That rib could have been present on some because they changed stuff all the time but you can see if somebody shortened a G shaft if the staple holes are not centered.
On some the boss for the mixing chamber cover screw extends to the fuel inlet, others it doesn’t. Note one of these has the original bowl and the other the later flat bottom replacement bowl.