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Old 11-04-2014, 11:23 AM   #1
Terry,NJ
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Default Two things I don't get! (Carbs and Ign)

Well, I put the "new" engine into the coupe and it runs worse than the old one! How so? you might ask. The mod B carb. and (I suspect) the ignition.
While the engine feels strong when it surges it will often break up after a few seconds. It feels like it's running out of gas and frequently barks a backfire like it's running lean, yet I can't seem to affect it much by trying to enrich the mixture with the GAV rod. The carb has been taken apart and throughly cleaned a number of times with no difference or any problems being discovered. Same with the fuel lines, filter bowl, and gas tank. It is one of the later mod. B carbs.
The engine starts very well and idles a little fast. The problems are when I accelerate it. In the driveway with no load it accelerates good, but on the road, with a load, it breaks up. It also has a random miss in it. The engine has new rings, timing gears, valves and valve springs, spark plugs. Is it my distributor, condenser, points? The points and condenser are the modern type.
Terry
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Old 11-04-2014, 12:10 PM   #2
AL in NY
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Default Re: Two things I don't get! (Carbs and Ign)

Did you remove ALL passage plugs and clean those passages? GAV has to be removed and passage cleaned under that also. Did you flow test the jets?
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Old 11-04-2014, 12:27 PM   #3
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Default Re: Two things I don't get! (Carbs and Ign)

you need to determine if its spark or fuel.
use an inline spark tester to check for erratic and or weak spark when running under load

Last edited by Mitch//pa; 11-04-2014 at 01:26 PM.
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Old 11-04-2014, 12:35 PM   #4
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Default Re: Two things I don't get! (Carbs and Ign)

to ck for a lean mixture,
richen the fuel mixture while running under load you can bypass the carb by spraying carb cleaner with a straw into the vacuum wiper hose when problem occurs
if the motor picks up then you have a lean fuel condition,ie, carb,, supply,etc

Last edited by Mitch//pa; 11-04-2014 at 01:11 PM.
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Old 11-04-2014, 12:55 PM   #5
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Default Re: Two things I don't get! (Carbs and Ign)

Float set too low?
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Old 11-04-2014, 01:18 PM   #6
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Default Re: Two things I don't get! (Carbs and Ign)

lean
try a diff carb
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Old 11-04-2014, 01:22 PM   #7
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Default Re: Two things I don't get! (Carbs and Ign)

Does this carb have the spring on the float and are you using a pump or gravity feed?
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Old 11-04-2014, 02:18 PM   #8
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Default Re: Two things I don't get! (Carbs and Ign)

Point gap has closed up.
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Old 11-04-2014, 02:23 PM   #9
Terry,NJ
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Default Re: Two things I don't get! (Carbs and Ign)

Answers; Al, No I blew them out with 100lbs of compressed air from both ends. They were all clear.

Mitch, I don't have an inline spark tester. I have never seen one. I am thinking of pulling the carb apart again and paying particular attention to the GAV valve/jet

Ray,I thought that might be the case a year ago so I raised it a small amount to no avail. It's now level with the top of the carb.

T-bird, I've been think of that since I have the old A carb. Maybe I'll try that this afternoon.

Bettlesr, It did have the large flat bronze spring on the float, but I removed it last year.

Fiddly, I checked that about three weeks ago when I started having problems with the old engine. Trouble is, everything looks oK, Fat blue spark, good gas flow etc. but she don't run too good, strong surges then it breaks up, and the constant intermittent miss.
Terry

Last edited by Terry,NJ; 11-04-2014 at 02:38 PM.
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Old 11-04-2014, 02:29 PM   #10
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Default Re: Two things I don't get! (Carbs and Ign)

A friend of mine just had a similar problem. Car idled OK but stepping on the gas resulted in sputtering and the engine just quit. Turned out to be the wire in the distributor going from the lower plate to the upper plate was frayed. He has modern points and condensor but traditional lower plate and wire going to the upper plate.

I always think that 80% of perceived fuel problems in the Model A are electrical problems.
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Old 11-04-2014, 03:21 PM   #11
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Default Re: Two things I don't get! (Carbs and Ign)

It could very well be ethanol gas, mine did about the same way because of the gas. Its probably been sitting a while while you were overhauling the engine. Ethanol gas goes bad pretty quick no matter what additives have been added. Once one starts acting up because of bad gas, just draining and installing fresh gas doesn't always fix it right off .
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Old 11-04-2014, 03:47 PM   #12
Mitch//pa
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Default Re: Two things I don't get! (Carbs and Ign)

try post # 4

this is a spark tester
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