1928 Model A

I have a 1928 ford model A that’s been in in the family for a long time. It has run really good since we restored it 3 yrs ago but now I’ve started having a little trouble. When I first take it out on the hwy it will go up to 50 and I don’t push it past there, which has been fine the last few years. but on my last few trips the ride out has been fine and the ride back has been bad, its been backfiring and losing speed, it runs fine at the lower speeds up to about 40, just wont get up to the higher speeds like it should. my auto knowledge is pretty basic, but I would think that its a lack of fuel, should I replace/clean the carborator or is it something else? I live right off the highway, so unfortunately highway driving isn’t something I can avoid.

thank you in advance for your help!

Cool. Really cool.

Let me suggest you do a search of 1928 Model A sites. Fuel deliver systems have changed greatly since 1928 any speciific knowledge might be more helpful.

Also, you may want to stop at a major bookstore. I know there are countless books specifically devoted to the systems of the Model A, and you may find pupchasing a few will help you greatly.

Here’s one: http://www.mafca.com/

thanks to both of you I will that out!

Possibly stuck in open loop operation :).

It sounds as though the mixture may be too lean. It may be that on your return trip the engine is hot and something expands so that air is being sucked in. You may want to check the gasket between the carburetor and the intake manifold. You might even begin by checking to see if the bolts holding the carburetor to the intake manifold are tight. Another possibility is the gasket between the intake manifold and the block.
The only vacuum line that I can think of would be the line going to the wiper motor. You might check to be certain that this line doesn’t have a hole in it that would lean out the mixture.

Have you checked the valve adjustments ?

One other thing is that the condenser in the distributor might be breaking down when it gets warm. Check the ignition points. If the points show pitting, the condenser may be at fault.

Fuel filter clean? Make sure that you don’t have debris in the gas tank that is obstructing gravity flow out. Gas cap must vent air in to let fuel out. What happens when you turn the mixture control rod on the lower right side of the dash to richer or leaner?