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I think of a carb being just like a spray gun. The flow of air from the engine going through the carb venturi creates a low pressure which pulls the fuel through the jets and mixes it into the air stream, just a like a paint spray gun. More air flow means lower pressure which means more fuel. So the fuel varies up and down directly with the amount of air going into the engine.
This is all well and good till you start climbing a hill. As you start pulling the hill the engine slows down. This means less air flow which means less fuel, just when you need more. And as you press the pedal down, that opens up the butterflies which lowers the vacuum in the engine even more. This is why they added the power valve. As the vacuum drops the power valve opens a aux fuel passage to the engine and lets more fuel pass through, feeding the engine more fuel even though there is less airflow.
I agree it doesn't show your carb tag of E4TE-AMA. However, it does show your component list of 95.2AK, which I've circled in orange. So, something is awry in the catalog or Gary's interpretation thereof.
Also, NAPA's parts listings refer to this carb (E4TE-AMA) as a high altitude carb, but based on the calibration numbers, this is not a high altitude carb... what gives?
I don't see it used in any Hi-altitude configurations. Do you? I trust Ford more than NAPA.
I agree, I don't see any Hi-Alt. either. I tend to trust Ford more too, just wondering if the kit NAPA lists is in fact for the AMA and the Hi-Alt. is there by mistake or the other way around... hmmmmm
As for buying a PV, would you have any qualms about using an NOS power valve. I don't know if they can fail while "sitting on the shelf" or not.
I'm just looking in the illustrated parts section now for a Motorcraft rebuild kit and notice that the page number of section 95 that my carb number refers me to says it's a feedback carb. Is this correct. How do I differentiate between feedback and non-feedback?
I agree, I don't see any Hi-Alt. either. I tend to trust Ford more too, just wondering if the kit NAPA lists is in fact for the AMA and the Hi-Alt. is there by mistake or the other way around... hmmmmm
As for buying a PV, would you have any qualms about using an NOS power valve. I don't know if they can fail while "sitting on the shelf" or not.
When buying carb parts you need to buy the newest possible. They had to change the composition of the rubber components to tolerate the ethanol fuel they sell now. That stuff is terrible on the older rubber components. Even with the newer carb kits the ethanol fuel is still bad for carbed engines if they sit around too much.
Gary, could I ask you a question about this power valve stuff again? I just ripped apart my carb and I thought it was supposed to take a two-stage but it only has a one stage in it and I know it is supposed to have a one stage in it because of the shallow valve cover. Bear in mind, this is not the original carburetor. It came off of a 77 Bronco. So I know you said in this thread that you shouldn't use a two stage valve in place of a one stage as it can cause more problems, but if the carb that is supposed to be on this truck is supposed to have a two-stage valve, that shouldn't introduce any problems, right?
I know that I'll have to find the correct depth cover... hopefully some NOS ones exist somewhere.
I don't think I said, or at least I didn't mean to say that you shouldn't use a 2-stage valve in place of a single stage valve. In fact, I like the idea of a 2-stage valve as it allows you to run the carb leaner than with a single-stage valve w/o suffering a lean sag until the valve opens. So, if you can find the right cover give it a try.
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