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Old 01-23-2021, 04:10 PM   #21
Synchro909
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Default 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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Old 01-23-2021, 06:09 PM   #22
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Default 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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Old 01-23-2021, 06:18 PM   #23
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Default Re: Dirty Carburetors

Quote:
Originally Posted by Gene F View Post
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?
Try doing that again and open the GAV. I suspect it will get up and go.
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Old 01-23-2021, 06:32 PM   #24
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Default Re: Dirty Carburetors

I did open it some, before I posted that.
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Old 01-23-2021, 06:33 PM   #25
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Default Re: Dirty Carburetors

B carb, by the way
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Old 01-23-2021, 06:38 PM   #26
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does anyone use an in line filter bettween sediment bowl and carb?
I do.....
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Old 01-23-2021, 07:00 PM   #27
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I do.....






It was one of the first things I did. I use a filter in the line inside the car so its less noticeable. Many say that doesn't/won't work, so, just don't tell my car that. Its been running fine like that since 1975 so I don't want it to get any bad habits.
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Old 01-23-2021, 07:47 PM   #28
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Default 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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Old 01-23-2021, 08:03 PM   #29
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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.
I run the Wix 33039 filter in the sediment bowl also.
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Old 01-24-2021, 03:12 PM   #30
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Default 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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Old 01-24-2021, 03:21 PM   #31
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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
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Old 01-24-2021, 03:25 PM   #32
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Default 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?
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Old 01-24-2021, 04:04 PM   #33
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Default 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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Old 01-24-2021, 05:35 PM   #34
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Default 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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