vacuum advance
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Tuned
Joined: Nov 2004
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vacuum advance
is there an easy way to see if my vacuum advance is working? i'm just wanting to see that everything is working properly. its a '77 f-250 w/ a 400 auto, all stock. also,what would cause steady low vacuum? i cant find any leaks, and the best i could get is about 10".
Posting Legend
Joined: Sep 2001
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The old shade tree way is take a clean piece of hose and put one end on the vacuum mechanism and the other end in your mouth, suck hard... Watch the mechanism move.
If you can't hold the vacuum with your tongue on the end of the hose you have a bad diaphragm. We have hand held vacuum test pumps for this testing also.
Your carb may not be adjusted properly, the timing may be off, or your cam timing may be off. An internal vacuum leak is possible.
If you can't hold the vacuum with your tongue on the end of the hose you have a bad diaphragm. We have hand held vacuum test pumps for this testing also.Your carb may not be adjusted properly, the timing may be off, or your cam timing may be off. An internal vacuum leak is possible.
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From: chicago burbs
i check the advance by connecting it to direct manifold vacuum. with a timing light hooked up you can see exactly what it's doing. disconnect everything and cap it and see what kind of reading you get. keep an eye on the gauge as you re-connect everything one at a time to see what is causing your leak.
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Tuned
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Originally Posted by grclark351
i check the advance by connecting it to direct manifold vacuum. with a timing light hooked up you can see exactly what it's doing. disconnect everything and cap it and see what kind of reading you get. keep an eye on the gauge as you re-connect everything one at a time to see what is causing your leak.
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