Acceleration problems

[nkaminar]

16 miles per gallon and 45 mph = 3/16 quart per minute or 5/8 quart in 3 minutes and 20 seconds. If you are accelerating or going up a grade the car will require more fuel. The fuel flow seems a little slow to me. Or maybe not.

On to the ignition.

Did someone stick a potato in your exhaust pipe?

[Rob Doe]

Originally Posted by History

when I hold the choke closed at a certain point it seems to run much better (sitting in garage with me inside car).

If this is repeatable, as stated above, this is an indication of a lean condition. Since you tried a known good carb, FROM A CAR THAT IS CURRENTLY RUNNING GOOD, and got the same lean symptoms:

Perhaps remove the fuel line at the carb again and attach a 1/4 " fuel hose and blow back through the line with the fuel valve open to temporarily clear the line??? Do you have a pencil filter in the top of the fuel valve?

[Rob Doe]

Originally Posted by History

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.

While waiting on the manifold gaskets, you could try to verify that there is an intake leak using a can of WD40 with the red straw, or an unlit propane torch. Take proper precautions.

[Charlie Stephens]

Check to be sure the throttle is opening completely against the stop. Be sure to post what you eventually find.

Charlie Stephens

[Marshall V. Daut]

Aha! Charlie finally hit a point that I have been waiting for someone to mention. Often when owners discuss lack of power from their Model A's, they don't realize that although their carburetors have been cleaned and rebuilt and the fuel flow checked, there is still a good reason the engine doesn't seem to reach high speeds. When guys swap from a Zenith to a Tillotson (or Marvel), they don't notice that the travel of the throttle arm is the not the same. It's impossible to sit inside the passenger's compartment with your foot on the accelerator and check whether the carb's throttle is pegged against its stop. And you can't check that from inside the engine compartment by pulling on the arm. That will give a false result because of the leverage your hand imparts that is lacking with your foot to the floor. This needs to be checked by two people: one holding the accelerator button to the floor inside the car and the other one checking whether the butterfly arm pegs wide open. Often times when a Zenith is at full throttle when the foot feed is floored, a Tillotson that replaced it might only open to 3/4 throttle, and visa-versa. I have yet to see many accelerator linkages (where the rod connects to the carb) that haven't been "adjusted" in their 90+ year lifetimes. Most of the arms have bends in them from past owners tweaking their throttle linkages to achieve full throttle.
On Model A's I have bought and repaired over the years, or for customers/friends, more often than not a different carb had been installed by the new owner or a past one, but the throttle linkage arm had not been commensurately adjusted (bent) to accommodate for full throttle. The first thing I check when someone complains about his lack of top end is the butterfly arm travel. I almost always end up bending it to achieve full travel. The owners are shocked by how much faster and peppier their engine is once full throttle has been attained. Well, Duh!!! ANY engine will feel underpowered with only 3/4 throttle! The Model A engine is more than capable of reaching 55mph, but unless it can also reach full throttle, it won't get there and owners will be disappointed in their car's performance. I suspect owners who complain that they can't get their Model A to go faster than 40-45mph may have a misadjusted accelerator linkage, assuming the speedometer error is within acceptable tolerances.
Check out the throttle arm travel with a friend and see if that helps you attain higher speeds with more power. Also check that the upper floorboard isn't prohibiting the accelerator linkage from full travel. Oftentimes poorly-made floorboards or ones with too much sound-proofing will stop the accelerator linkage from going down all the way. Make sure the arm beneath the accelerator button is not chafing against the hole in the upper floorboard. If so, bend the arm beneath the button to clear any interference around the hole.
Marshall

[History]

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I checked float level again and it is right at 5/8” from the bottom of the top half of carb. (Pictured). I decided to check things out in the bottom while I had it off and there was some crud on the gav needle tip so I cleaned all again AND it runs correctly now. I did blow back through the fuel line as I do have a pencil filter on it, it didn’t push fuel back toward me so cap is venting. I don’t understand why the good carb didn’t run well. Maybe I’ll put it back on now and see if it runs well also. I’ve had waaaayy to much going on so I’m a little scatter brained on top of being born scatter brained. I had already blown through the fuel line so I don’t believe it was that. I really appreciate all of your responses and they all could have been the culprit but I’m thinking at this point it was the crud.

[shew01]

Wow. I’m glad you found the issue.


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[nkaminar]

Progress. Good work. The spray carburetor cleaner can sometimes work wonders.