Where is ported vacuum?
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Where is ported vacuum?
Ok so as you guys know I am tackling the Duraspark swap on my truck. An the new distributor dropped in Like gold. I bumped the engine over a few an she sled in. Got her to crank and run. And she is running good. I have no timing light so tomorrow I will be tuning everything by vacuum gauge. But the only thing I am scratching my head on is ported vaccuum. And to my knowledge to find ported vaccuum :you look for a vacuum line with little to know vaccuum on it until you crack the throttle open then vaccuum increases as rpms. That's my understanding. But I just can't find it. I am running the feedback carb , so is there anyway I can get my vacuum advance going. I know you cant use manifold vacuum because you will hit max advance quick and your power would be poop......I think. Is there any line I can tie into and pull vaccuum for the distributor? All advice is welcomed and needed.
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Oh sorry about that I have a 86 f150 with the 4.9 and a one barrel feedback carburetor. It's a amazing from from just messing with the swap my truck is no longer running crazy rich. I can actually be in the engine compartment and not have asthma or burning eyes . But I really need to know about this ported vacuum situation its kicking my tail. Thanks guys.
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Since you are running the feedback carb, you will have no spot for ported vacuum. You need to go all the way and change the carb also.
You can try manifold vacuum, it doesn't hurt anything except your idle speed and idle adjustments. Once you get going there is no difference.
But the idle problems with the manifold vacuum may give you driveability problems. The idle speed will be very high and you may run out of adjustment to bring it back down.
What I would do for now till you get another carb is just run without vacuum advance hooked up. It will not affect your power output at wide open throttle, it will just affect your fuel mileage at part throttle. If you set the timing by ear, you can still get some of your fuel mileage back by setting the base timing up a little bit.
You can try manifold vacuum, it doesn't hurt anything except your idle speed and idle adjustments. Once you get going there is no difference.
But the idle problems with the manifold vacuum may give you driveability problems. The idle speed will be very high and you may run out of adjustment to bring it back down.
What I would do for now till you get another carb is just run without vacuum advance hooked up. It will not affect your power output at wide open throttle, it will just affect your fuel mileage at part throttle. If you set the timing by ear, you can still get some of your fuel mileage back by setting the base timing up a little bit.
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I think I will go with manifold vaccuum. Take a look at this .
Classic Inlines - Vacuum Advance
In short they were sayin I need full vaccuum. It also tells me I need a timing light an I need to learn more about timing. How should I go about adjustments with full vaccuum.
Classic Inlines - Vacuum Advance
In short they were sayin I need full vaccuum. It also tells me I need a timing light an I need to learn more about timing. How should I go about adjustments with full vaccuum.
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Read the first paragraph of that article again. They say there is no right or wrong way to do it, but when the fuel/emissions system is designed at the factory, they do design it with one way in mind, and sometimes you can have trouble changing it.
The first thing I would do is get everything changed around, and leave the vacuum advance disconnected. Then put your timing light on it, and set the initial timing according to the original sticker on the radiator. After this, you should be back to where you started before the changeover.
Then, with the engine running, plug your advance into the manifold vacuum port. You will instantly know what you have to do after that.
The first thing I would do is get everything changed around, and leave the vacuum advance disconnected. Then put your timing light on it, and set the initial timing according to the original sticker on the radiator. After this, you should be back to where you started before the changeover.
Then, with the engine running, plug your advance into the manifold vacuum port. You will instantly know what you have to do after that.
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Yeah I understand about no right or wrong way. This morning I rose up and cleaned up the engine bay with all the wires and stuff removed everything and pulled all unneeded ports on the tree. I wanted vaccuum advance to be used so I ran manifold vacuum to the distributor. The run runs great. She idles a little on the high side when in park but nothing to bad. She now RUNS. I mean I can light up my tires all the way now. With a little one barrel! I can't wait to go all into the build. I may check the timing out of curiosity but feel as if its was a major success . Oh my air fuel mixture screw doesn't really do much.
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Your air/fuel mixture screw doesn't have much affect because your idle is so high. The carb has different fuel circuits inside it, when the rpm is low the idle circuit kicks in, and that is what the screw adjusts. There are also transition fuel circuits that add fuel above the idle, but below the main circuit, and then there is the main fuel circuit. If your idle is high, the other fuel circuits will be adding fuel, so that makes the idle circuit adjustment screw have little affect.
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