Proper jet size for a 1920 carb?

[timk225]

I acquired a '73 Duster recently, typical 225 1 bbl automatic car. The story I got was that this car sat for a good 20 years, so before I even try to start it, I am doing a lot of maintenance. I already changed the oil and filter, pulled the spark plugs (a set of Splitfires), and put around 3 ounces of Marvel Mystery Oil into each cylinder. Then spun the engine with the new battery for around 20 seconds until the oil pressure gauge came up around 60. Did that a few times over a couple days.

I've got more to do, like changing the vacuum lines, and taking off some of the crazy add-ons the previous owner put in the car.

But for the carburetor, a 1920 Holley, I think it is a #R7031, I took it all apart for a rebuild, and it definitely needed it. Lots of hard gunk, accelerator pump was locked solid. Took a knife, screwdrivers, and a whole can of carb cleaner to get it cleaned up pretty well. I shot a lot of cleaner through every hole I could find.

For the main jet in the carburetor, I cleaned it up and looked at it, it has the number 612 stamped on the side. Does that sound right? Is it a stock size jet?

 

[townsend]

Chrysler used 6 different Holley 1 barrel carbs in 1973.
The R-7031 is a Holley replacement for all 6 of the original part numbers.
Let's say you went into a store that sold Holley carbs in 1978 and gave them any one of the 6 numbers stamped on the original carburetor. The Holley replacement would have been R-7031 for all of them. Most likely that is the original jet.