Acceleration problems

[History]

I rebuilt the carburetor and believe I did that correctly as it ran well then. I did have to clean the plugs as they were covered in black soot and it ran awesome. That was a year or so ago and it’s sat since then. I’ve never driven it any distance on the road, just around my shop area. I just redid the brakes and brake/clutch shaft and jumped on the road and it will not accelerate smoothly. It acts as though it’s starving for fuel (backfiring during acceleration)but I don’t believe that’s the problem as I borrowed a known (good) carburetor and it ran the same. My fuel flow looks great to me so let’s assume it’s adequate. I checked the timing and it seems correct, cleaned plugs again, set points 20 thousandth. What would you guys recommend to look at and what order? I appreciate any help you can give.

[lrf]

You said the car sat for awhile, there's a good possibility that the points are oxidized so clean the points by pulling a clean strip of paper between the closed points. You don't need to use sandpaper, the old timers use to use a match book cover drawn through the closed points. Hope this helps. Keep driving your "A".

[Synchro909]

"That was a year or so ago and it’s sat since then."
Did you replace the fuel? 12 month old fuel doesn't run as well as fresh stuff does. The engine loses its sparkle.

[Bob Bidonde]

I suspect 2 things: 1) Poor grounding of the ignition to the battery; 2) Try replacing the condenser.

[History]

New fuel with no corn it before or after. Will check ground and make sure points are cleaned. Thanks guys

[bruceincam]

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I'm just passing on my experience with an identical problem. My problem ended up at the coil. Once I replaced the coil, no more backfiring on acceleration.

[Gary WA]

Check for manifold leaks..

[Rob Doe]

X2 on #7, at carb to manifold, intake manifold to block, at the vacuum wiper line, and at the throttle plate shaft. Check the thru bolt holding the carb together is snug.

Where is your GAV set? 1/4 turn ccw from fully closed? Did you try opening it a small amount multiple times?

Are you driving the car when this happens or are you manually manipulating the throttle in the drive and it misses and backfires at higher rpms?

[old ugly]

i know you said you tried a different carb, to one you know is good. and you said the fuel flow is good.
to really check the fuel flow to the carb run a line from the carb line into a bucket, then turn the gas on and let it run for a while. sometime the initial flow will look good but then it will slow down. if it slows then there is a partial plug in the line or the tank is not vented. if it runs continues then move on to from the carb.

[Patrick L.]

One thing not mentioned is the fuel line ferrule. Make sure the line doesn't protrude past the ferrule too far which can restrict the flow.


Where is the spark lever set when this happens ? Once started the lever should be down 1/2 to 2/3.

[jack backer]

‘If you think it’s a fuel problem then it’s an electrical issue, if you think it’s electrical it’s fuel’


old mechanic proverb

[History]

I just got a chance to look at it again and here are the findings,,,,cleaned points but they looked good, changed coil wire, exhaust manifold gasket is blown on front cylinder (maybe from backfiring) and when I hold the choke closed at a certain point it seems to run much better (sitting in garage with me inside car). Where/ what is recommended intake/exhaust gasket and to buy??

I will check the flow again as suggested and let it run enough to see how long a gallon takes to run out.

Spark lever half way down

[Rob Doe]

I'd fix the manifold gasket. If the exhaust is leaking the intake may be also. Do one thing at a time so you know what fixed it. I torque the intake and exhaust manifolds on my car at 25 foot pounds and come back after a few miles to make sure it is still tight. After a couple checks I go every 500 or so before checking again.

[nkaminar]

I have had the best luck with the original gasket, see https://www.snydersantiqueauto.com/p...htm?pid=979402

Torque the nuts to 55 ft-lbs and use the conical washers. Make sure the manifold is flat by setting the exhaust and intake manifolds bolted together on a flat surface. If they are not flat you can sand them using 80 grit sand paper that is glued to a flat surface. Check the torque after one drive and then again after a few hundred miles.

Check the fuel flow by removing the smaller bolt under the carburetor. Use a bucket to catch the fuel. Do this outdoors with a fire extinguisher handy. By checking the fuel flow there you take into account all the fittings, lines, filters, and float valve. If you get low flow at that location you can isolate each component one at a time to find the fault.

You can use the clear distributor cap to view the sparks while the engine is running. They should all be blue and uniform.

[Patrick L.]

If it runs better with the choke partially closed then its probably running too lean. So there is an intake/carb gasket leak somewhere or an improper low speed idle mixture adjustment.

The suggestion of opening the GAV in increments is a good one. Not all carburetors are created equal. They all tend to have their own preferred setting from closed to a turn open.

[jetmek]

Check your float level

[ronn]

you can also shoot some carb cleaner in the carb, while its running.......

[History]

I believe my flow to the carb is adequate, I tested it by using a quart measuring cup. Had my son to turn it on and I watched and timed it. To run one quart it took 1 minute and 10 seconds, so a gallon would be over 4 1/2 minutes. I believe that is more than adequate so we can rule out a restriction in fuel supply to carb. The line just sticks past the Ferrell into the carb so I think it’s ok as well.I’ve ordered new manifold gaskets and will replace them soon. There could be leaks there now on intake but it’s hard to tell. I think the float level is good because of the other carb doing basically the same thing.

[ronn]

wasnt speaking on fuel restriction- more on cleaning out jets, float etc.


taking any gum out of carb and free flow

[History]

Took 3 minutes 20 seconds to run a quart through the carburetor. I don’t know what rate should be but it seemed more than sufficient to me. Carb doesn’t appear to be gummed to me as the known good carb runs the same.