Ok im pretty much a novice when it comes to working on slants, so I might need a little extra information here. My engine recently got rebuilt. Before the rebuild I was getting 10mpg and my tail pipe was shooting out this black carbon crap and smoking brown and blue smoke when I would nail the throttle. So now the engine is rebuilt and im still only getting 12mpg with the carbon and smoking (just not smoking nearly as bad). The mechanic's at the place that rebuilt my engine told me that the carb is running extremely rich and is at 10% C/O. They said it needs to be down to 2% but it can't be done just by adjusting the screws. They also told me that I need smaller jets. So before having to take it back to them and paying even more, I figured I would mess with it myself so I can learn how to work on this darn thing and maybe save some money.

So now I have a carb kit and a guy who is decent with carb's that is gonna help me rebuild it next week. I was just wondering if anyone had any tips that the instructions don't mention when it comes to rebuilding the Holley 1920? Also what size jets should I get? Im much more concerned with fuel economy rather than performance. Any tips would be appreciated. Thanks.

The year of the carb "kind of" determines the jet size, the old 60's carbs came with everything from 55's to 57's.....56/57 should be fine, 55 is a bit lean in every instance, 58 is the max size for the 1920.

You should get it opened up and see what jet you have, if it's a 56 and they said it's too rich, either they don't know what they are doing or your carb has another problem...


-D.idiot

I agree. If that Holley is the original carb (I have a 1920 on my '70 Duster w/225), then those jets should be spot on, unless someone has changed them over the years. Sounds to me more like your float is old, and taking on fuel (heavy). It's an easy carb to work on. Take 'er apart and see what's up!

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DynoDave
1970 Plymouth Duster
1972 Dodge Charger Rallye
1977 Chrysler Cordoba
WPC # 12304

Its one of those remanufactured jobs from Kragen

I didnt know they were garbage when I bought it a couple years ago.

Low cost carb "remanufacturers" are known to drill-out the factory jet(s) and set the carb way rich, this covers-up other problems the unit may have.
Bottomline, you can't trust the number stamped on the jet, it may have been drilled-out.
DD

So with this carb, would it be a good idea to go ahead and buy 56's anyway?

I would run a #58. In my experience, it seems the best for fuel economey (around 22mpg in my 3600+lb Satellite) and still be able to get good power (not run out of breath over 60).

So I rebuilt it today. Opened up the thing the float sets in and noticed I had a ball bearing just rolling around there. So I looked around and found a spring just sticking out of that piece where theres the two holes with the springs held in by the ball bearing and ring piece to go on top. The right one apparently came off at some point. Im guessing thats the reason why I was getting 10mpg? I took the jet out and it said it was a 52. Is that pretty bad? You guys were saying 56-58 while I was running rich with a 52. Should I replace the jet anyway or was I running rich because of the spring deal that came apart?

Yep, you've found the problem (or, at least you have found part of the problem.)

've posted before about a Holley 1920 I once had on my '65 that exhibited strange behavior: The engine ran very well and had fine power, but was suspiciously easy to start and drive from cold (zero choke required, just hop in, turn the key and drive off without any stalling or gasping...even with the choke disconnected!) and the car was getting under 10 mpg. Turned out the brass seat ring that retains the power valve check ball, had fallen out of the metering block. Result was that the power valve was always WIDE open. I put the metering valve back together and restaked the seat ring, and things went back to normal (20mpg, choke and careful cold driving required). That metering block inside the Holley 1920 has all kinds of tiny passages and check balls that can make problems without any outward signs...

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

You have a later 1920 with a 2 stage power enrichment valve. (power valve) Holley calls this the "economiser valve" in the 1 bbl carbs.

A missing ball at this fuel feed control point would make the carb run rich.
Once repaired, I doubt that the engine will have any power or even come off idle with a #52 main jet. (unless that jet has been drilled-out to a larger size)

Make the repair, complete the rebuild with a "know size" main jet and test the carb's performance. Adjust as needed.
DD

Dan, that sounds a bit like my car. Doesn't take much time, if any time, to warm up in the mornings. I'll check the mileage this week to see if things are a little more normal. Although im still getting more black smoke out of the tail pipe than I want.

Thanks Doc, I'll put a new jet in when I get some time this week. After hearing about all this, im pretty weary about the jet actually being drilled out because its not running bad like you described it would with a 52 jet.

There could be other "leak points" in or around the metering block, that could explain why it has such a small main jet, compensation for fuel entering in into the system somewhere else.
DD