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01-23-2021, 08:04 AM | #1 |
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Dirty Carburetors
Dirty carburetors tend to be a frequent theme on this site. Many folks post about cleaning them out to get better performance.
I remember in the late 1970s and 1980s, Citgo gas tended to plug up carburetors in my area. (I’d have to use aerosol carb cleaner to cure hesitation in my cars back then fairly frequently. I switched to BP and Exxon, and I stopped having that particular problem so often. If I recall correctly, I think these are called top tier brands and are supposed to keep the carburetor cleaner.) Murphy (at our Walmart gas station) sells ethanol free gas, and I always add Marvel Mystery Oil when I fill up. So far, I’ve had my Model a for about a year and a half, and I don’t seem to have any carburetor issues. I suppose not having an air filter would allow the carb to suck up more dirt. (I know there has been a lot written about the virtues and perils of running or not running an air filter.) Was a dirty carburetor a common issue in the 1930s and 1940s? Have you noticed one brand or type of gas causing more issues than another? What are some ways to keep carburetors from getting dirty in the first place? Sent from my iPhone using Tapatalk |
01-23-2021, 08:26 AM | #2 |
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Re: Dirty Carburetors
I cleaned my carburetor last fall and at the same time cleaned all the jets and replaced the gaskets. The GAV was not up to the mark so I replaced that assembly. The carb was indeed dirty but I do not know when the last time was that it was cleaned either. TO me, cleaning the carb and jets "baselined" the carb for me. I also run my A with the engine pans.
Other member in my club do not run with air filters. I try to purchase Ethanol Free when and where I can get it. Compared to the 30s and 40s most roads are paved now....with the exception of the 600 yard long dirt road I live off of. :-) I am not expecting carb cleanliness to be a big issue. If I have to clean it once a year after driving less than 1000 miles...so be it. A labor of love. But I will report back at some point about how clean my carb remains. Planning, still on doing some driving at the MAFCA NH tour in June. |
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01-23-2021, 08:40 AM | #3 |
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Re: Dirty Carburetors
The key is to make sure you have all the proper filters installed.
Pencil filter in the tank, sediment bowl screen and filter and carb filter. With todays roads a carb air filter is probably not going to make much difference as far as filtering more particles. |
01-23-2021, 08:57 AM | #4 |
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Re: Dirty Carburetors
When you have those carburetors off to play with them, make sure that top flange is flat. Hit it with a large file to make sure.
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01-23-2021, 09:04 AM | #5 |
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Re: Dirty Carburetors
I totally agree with your assessment. Good common sense. Wayne
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01-23-2021, 09:07 AM | #6 |
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Re: Dirty Carburetors
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01-23-2021, 09:23 AM | #7 | |
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Re: Dirty Carburetors
Quote:
That’s an excellent point. I hadn’t consider that. Sent from my iPhone using Tapatalk |
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01-23-2021, 09:29 AM | #8 | |
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Dirty Carburetors
Quote:
I don’t know if there is a pencil filter in my tank or not, but I’ll probably need to replace my fuel shutoff and check on that filter when the weather gets warm. It’s starting to weep just a bit. I presume my glass sediment bowl has a screen. It seems to be collecting a little bit of dirt. There isn’t much in the bowl yet. I’ve heard they are prone to leaking; so, I’ll probably wait a while before I break it open. The previous owner installed a carburetor filter, and the filter does collect dirt. I’ve changed it once. Sent from my iPhone using Tapatalk |
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01-23-2021, 10:39 AM | #9 |
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Re: Dirty Carburetors
does anyone use an in line filter bettween sediment bowl and carb?
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01-23-2021, 11:15 AM | #10 | |
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Re: Dirty Carburetors
Quote:
Before you remove your sediment bowl, get a new cork gasket so you can replace it. Sometimes the gasket comes off partially stuck to the glass and rips, not much good then. Worth a buck to just plan to put a new one on. Put a towel, bowl or something underneath it to catch the fuel as you loosen the bail. And turn off the gas valve at the tank first (DAHIK)! JayJay
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01-23-2021, 11:30 AM | #11 |
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Re: Dirty Carburetors
I tried every bit of advice and was collapsing the "micro filter" inside the sediment bowl. Someone suggested that these motors get angry when over filtered. I tend to agree. To each his own but the best combination for my car has been the pencil filter and a wix brand #33039 inside the sediment bowl. That's it other than the useless (imho) filter inside the carb itself.
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01-23-2021, 11:39 AM | #12 |
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Re: Dirty Carburetors
I spent a lot of time in years past cleaning carburetors, carburetors of all sorts. I don't think its too much of an issue today.
It does seem to be a pretty big topic here though. Once a carburetor is properly cleaned and adjusted they should bullet-proof for along time. As for an 'A' carb, whatever type it is, I run different ones at different times just for the heck of it. An 'A' is an 'A', they don't much care. In mine I run all the old stale gas I have hanging around from the mowers, weedeaters, outboards, chainsaws, etc. It doesn't care. But, I do use non-ethanol in those engines. When I pull in to a station for fuel with the 'A' I use the cheap ethanol stuff, there isn't much that can hurt our carburetors. I'm one that uses an air filter and an in-line fuel filter. |
01-23-2021, 11:45 AM | #13 | |
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Re: Dirty Carburetors
Quote:
Really? I’ll need to check that out when my tank is low again. And, I’ll need to order a cork gasket. I recently ordered a replacement shutoff valve, a pencil filter, and some spare gas lines (in case I need something up when I eventually take it apart in warmer weather), but I didn’t think about the sediment bowl. Sent from my iPhone using Tapatalk |
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01-23-2021, 11:49 AM | #14 |
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Dirty Carburetors
Does a carburetor tend to get dirty (on its own, maybe with corrosion of some sort) if it’s just sitting for a few years? That might help explain the frequent topic—often the posts are related to awakening a Model A from a long “sleep.”
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01-23-2021, 12:06 PM | #15 | |
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Re: Dirty Carburetors
Quote:
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01-23-2021, 12:15 PM | #16 |
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Re: Dirty Carburetors
I bet dirty carbs were commonplace back in the day. With no air filters or bad gas it probably took it's toll. I take mine apart about twice a year and spray carb cleaner thru it, then check all the filters and spray them out including the sediment bowl if needed. Doesn't take much time and seems to help keep things running smoothly.
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01-23-2021, 12:37 PM | #17 | |
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Re: Dirty Carburetors
Quote:
I have had better luck with Snyders vs the wix brand #33039. https://www.snydersantiqueauto.com/P...earchByKeyword |
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01-23-2021, 12:52 PM | #18 | |
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Re: Dirty Carburetors
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I’m curious. Roughly how many Model A miles do you drive in a year? Sent from my iPhone using Tapatalk |
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01-23-2021, 03:49 PM | #19 |
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Re: Dirty Carburetors
I do about 4,000 miles per year.
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01-23-2021, 03:59 PM | #20 |
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Re: Dirty Carburetors
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01-23-2021, 04:10 PM | #21 |
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Re: Dirty Carburetors
I am of the opinion that a lot of our carburettor issues these days can be traced back to the differences in fuel. Petrol (or gas as you guys call it) is a mixture of several hydrocarbons. There is a very wide range of them cracked out of crude oil. Back when these cars and their carburettors were designed, fuel chemists chose a group of hydrocarbons with similar boiling points etc so that hot or cold, any brand, they all performed pretty much the same. As demand for fuel rose, more and more hydrocarbons were included in the mix. Some had higher boiling points, some had lower. Then there are the additives for higher compression engines to maintain a high enough octane rating and "burn clean" additives. The demand these days is so high that fuel as we know, doesn't last long before it spoils and if left to evaporate, it leaves behind an oily residue. The more volatile hydrocarbons contribute to such problems as vapour lock, the lower ones to incomplete vaporisation and subsequent sluggish (lean) running. Fuel in those days more closely resembled aviation fuel of today than what we buy for our cars. Even though a Model A does not need anywhere near the high octane rating of Avgas, if the carburettor on your car is good, you will not believe how much better the car behaves on it. Sure Avgas is expensive but if you understood what I have written above, you will understand why and understand what a burden running a car in those days was for your average working Joe.
Computer controlled engines with variable cam shaft timing, fuel injection etc etc have made today's fuels acceptable in a modern engine but it is not so good in an old one.
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01-23-2021, 06:09 PM | #22 |
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Re: Dirty Carburetors
Was just our in my A and noticed it cruises nicely, but when I push the accelerator down to the floor "it falls on it's face". Let up a tad, and it's fine and pulls again.
I had the gas gage out a few weeks back, and the pencil filter looked fine when I shined a flashlight in there. Likely causes? I think I ran a coat hanger through the fuel line last time I had it off (no more than 1 1/2 year ago). Any likely places to start? I'll likely do the fuel line from the firewall, and the carb inlet screen, since they are the easiest to do. What else in order of likelyhood please? |
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01-23-2021, 06:18 PM | #23 | |
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Re: Dirty Carburetors
Quote:
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01-23-2021, 06:32 PM | #24 |
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Re: Dirty Carburetors
I did open it some, before I posted that.
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01-23-2021, 06:33 PM | #25 |
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Re: Dirty Carburetors
B carb, by the way
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01-23-2021, 06:38 PM | #26 |
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Re: Dirty Carburetors
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01-23-2021, 07:00 PM | #27 |
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Re: Dirty Carburetors
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01-23-2021, 07:47 PM | #28 |
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Re: Dirty Carburetors
I run an inline filter also have since 1993. The one I use was used for VW bugs.
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01-23-2021, 08:03 PM | #29 |
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Re: Dirty Carburetors
I run the Wix 33039 filter in the sediment bowl also.
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01-24-2021, 03:12 PM | #30 |
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Re: Dirty Carburetors
Good afternoon...Some of us in the desert simply put a good sized magnet in the glass bowl and let it pick up the rust as it comes through. It is easy to see when the magnet is full of 'stuff' and you need to open the fuel filter and wipe off the magent and clean the bowl...works well...doesn't cost much...Ernie in Arizona
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01-24-2021, 03:21 PM | #31 |
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Re: Dirty Carburetors
Well this morning I dropped the bowl section off the B carb. Blew it out and all. I did hear a little "pop" when I ran a small wire through one of the jets. Coat hanger through the fule line. Dropped firewall sediment bowl screen, and it was crystal clear, as I expected. Compressed air through carb, and fuel line. It is better, but still not 100% even when opening GAV abt 2 turns.
The float is just a tad high. meaning that the toe of it is just barely upward with relation to the mating flange on the carb. I was taught if your gonna go one way or the other go a bit high. Otherwise when ya drive around the corner the car will stall. I guess the only other thing I can think of is 1) change the pencil filter in the tank anyways.... 2) I |
01-24-2021, 03:25 PM | #32 |
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Re: Dirty Carburetors
2) Is it possible the carb was assembled the last time with he wrong jets? 3) put my Zenith back on the B manifold, and see if the problem goes away.
I have the big valves, Brumfield head, and the IB-330 cam, so if I don't solve this I kinda feel like I am leaving some potential on the table. I have an overdrive, but when I go up a hill I want that torque. Any ideas? |
01-24-2021, 04:04 PM | #33 |
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Re: Dirty Carburetors
The first thing you have to check is the end of your fuel line where it goes into the carb. If there is too much of the tube extending past the ferrule, the tube can be blocked when the tube end hits the horizontal filter in the carb. Happens a lot. Circumcise the tube a bit.
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01-24-2021, 05:35 PM | #34 |
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Re: Dirty Carburetors
I checked that, thinking there is a screen in there. None, cause I pulled that fitting and looked in there with a light. No screen in there. However, that's a good point. Easy to do, so I'll pull that off and check. If it's long beyond ferrell I'll cut it off a bit. Easy to do. Nice tip. Thanks. Lotta times its something simple...
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