Zenith carburetor adjustment

[scott12180]

My 1932 Packard 902 has a large Zenith carbuetor which a previous owner installed.    (The photo shows an identical spare.) I do not have a Detroit Lubriucator.

 

Could someone  tell me or point me to a website which goes into how I should properly adjust this carburetor?  Also I'd like to know which model carb this is.  Nothing written on it save for a circular brass tag with some numbers.

 

Am I correct that this  carburetor has an adjustable main jet?  Is that the brass screw-in thing on the lower right side?

 

Thanks --- Scott

32 Packard 902 Victoria Coupe

[Spinneyhill]

The brass tag is the key. Those numbers tell you what model it is. Look at http://thecarburetorshop.com/

 

[ArticiferTom]

http://www.carburetor-blog.com/manuals/marine_63m_manual.pdf Try this site .

[scott12180]

Wow, thanks very much.

I think that's it --- a Zenith Marine carburetor. I'll read it through tomorrow.

--Scott

[PFitz]

If that is your carb, check the power jet circuit. If it's clogged, or the vacuum piston isn't sealing enough, or the spring is weak enough  so that circuit will not respond well enough, that would make it run lean on hills.

 

A way to check is drive up that hill it pinged on again. As the engine starts to ping, slowly pull the hand choke out. At some point with part choke, if the pining stops and the engine seems to gain a bit more power then it was running too lean and you need to find out why the power enrichment circuit isn't compensating. 

 

Don't pull the choke out too quickly, or too far, because that will cause the reverse condition - the engine to be over choked and go too rich.

 

Paul  

[Owen_Dyneto]

I presume you already know that, while not inexpensive, you can purchase a correct reproduction Detroit Lubricator carburetor for your 902 Packard.

[edinmass]

I would NOT run that on a car. Most marine carburetors don't have accelerator pumps from that vintage. If you run it lean you can burn valves, melt pistons, and crack heads and blocks. New and used carburetors are available, they are not cheap, but worth every dime. The car should be tuned on a five gas analyzer if you are not going to run a factory carb. There are hundreds of experts, but almost none have a lot or pre war car experience in changing out carburetors. Be careful and don't make an expensive mistake by running an incorrect carb. Carbking will chime in, and take his advice. Ed

[ArticiferTom]

I do not think you have that exact marine carb .  that is similar and may be used to tune yours . also if you back in to the web site it has other listing . Get model number from brass tag maybe 63,67 263, 267 or some other ,then do search . they mostly are same if updraft . With instructions on web . Also Tractor parts supply has lots of universal rebuild kit with gasket for these oldies ,which where used on many of tractors .

[edinmass]

2 hours ago, edinmass said:

I would NOT run that on a car. Most marine carburetors don't have accelerator pumps from that vintage. If you run it lean you can burn valves, melt pistons, and crack heads and blocks. New and used carburetors are available, they are not cheap, but worth every dime. The car should be tuned on a five gas analyzer if you are not going to run a factory carb. There are hundreds of experts, but almost none have a lot or pre war car experience in changing out carburetors. Be careful and don't make an expensive mistake by running an incorrect carb. Carbking will chime in, and take his advice. Ed

 

I wouldn't run that carb at all, for any reason. Ask the members here if I know what I am talking about. Your asking for problems, that can get vary expensive. Ed

[scott12180]

The carburetor on the car is Zenith 10870B.   The spare shown in the photo is 11583D.   I can't find a chart explaining exactly what these are, but a Google search suggests that they both are Marine.

 

Some road testing today where, suspecting the carb is running rich, I closed the main jet screw half turn at a time to assess running.  It seemed to get better and better but then I noticed that the main jet was fully closed ! The car still ran great, which puzzles me (how can it run with the main jet closed???) , but on a short steep hill, it lost a lot of power presumably being too lean.   So is Paul "PFitz" correct that I should run it rich on the flat so it is compromised to be OK on the hills? It was one and one half turns open.   

BTW, if you do have a marine carb, there likely is no power enrichment circuit like a car needs. The lack of such a circuit will make it lean out on hills.  This was a problem with the marine/stationary engine carbs that were showing up as replacements for the potmetal carbs of the late 1920's.  They run ok at idle and on level roads, but with no way to properly enrich the mixture proportional to engine load, such as hill climbing, they go too lean. So, typically, the owner's opened up the main jet to "compromise" for hills and then the carb is running too rich when not under load.    Sound familiar ?  --PFitz

 

I still don't understand how the carburetor can run well with the main jet fully closed.

 

Iagree with Ed that I'd prefer to run a proper Detroit Lubricator but the reproduction ones are $3500, if they are even available.  That's a bitter pill to swallow right now.  Any suggestions for alternative sources?  Or other automotive carburetors I could try out?

[PFitz]

Running with the main jet closed is a classic example that another circuit in the carb is leaking fuel into the main discharge jet, or there is an internal crack between fuel circuits.   Similar situation with when the idle air screw has no affect on idle - there's a leak somewhere.  

 

Updrafts have submerged jets that some of which are often spring-loaded valves. When they age they tend to leak, thus becoming another main jet. Plus, most often those spring-loaded jets are brass. Alcohol in the gas contributes to surface erosion making them leak even if they are cleaned.  All-too-often, people who are not familiar with how updraft carb function will throw a "gasket kit" into the carb and think that will take care of it all.  

 

And just to be clear, I never proposed running the main jet "too rich".  I'm all for getting the proper size, and type, carb for that size engine.     I said compromising with the main jet to make up for a lack of a proper power enrichment circuit is what others have been doing in the past. Many who's late 1920's car had a potmetal carb that was falling apart,  and they bought a cast iron marine/stationary carb at a swap meet thinking that would solve their crumbling potmetal carb problem. 

 

 $3500.00 ?   What's it cost to rebuild your engine ? Because using the wrong carb can eventually cost you an engine rebuild. 

 

Paul 

Edited August 9, 2017 by PFitz (see edit history)

[edinmass]

Scott, that Carb is messed up. PFitz is correct on why it won't adjust. Your gambling with that engine running it. It's not worth taking a chance. I may know where there is a good factory carb, I'll ask about it today and get back to you. It's already running lean from what you are posting. Too many people just jam on any carb because it's about the same size or will bolt up easy. I have seen more than a handful melt down from running lean. Be patient, and get the right carb. Ed

[PFitz]

Looking through the marine carb listings at Jon's website, that Zenith 10870 is listed for Gray Marine A100 engines 1947 - 51.

It's listing starting almost 3/4 of the way down this page.   http://www.thecarburetorshop.com/MarinekitsG.htm

 

No listing there at Jon's of the 11583. But, another website listing of Zenith 11583 said it's Chrysler 1953-55. If it is, being an updraft that late it's possibly a marine cabin cruiser engine to give more engine hatch clearance ???? 

 

Paul

Edited August 9, 2017 by PFitz (see edit history)