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73-87 Chevy _ GMC Trucks => Performance => Topic started by: swilliams on July 11, 2014, 12:01:02 am
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I have run this carb for years runs good no problems. As I am upgrading and changing things I bought a vacuum gauge to help set up timing. With the engine warmed up I checked both ported and manifold vacuum and neither has vacuum except when I rev it then it jumps to almost 10" but does not stay it drops back to 0". Any info will be helpful.
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Sounds like your gauge is junk. If the motor is running, it should be pulling something.
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put your finger over the hole and see if it sucks it
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I sucked on the hose and the guage showed to hold pressure and I have put my finger over the holes and feel no suction. I know it sounds strange. Like I said when i rev it it pulls almost 10" but does not hold it but for a second. When I test the guage it will hold at what ever pressure I set it to. Also lately my brakes are hard to push at idle but when I speed up it gets better. The problem almost ssounds like a vacuum leak but the engine runs fine and I have also sprayed carb cleaner everywhere looking for a leak and have not been able to fond one.
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The timed (passenger side) vacuum port should not pull any vacuum at idle, but will jump up when you open the throttle plate, so that's normal. The manifold (driver side) vacuum port should pull vacuum at idle. Could the port be clogged, with a piece of vacuum hose or a chunk of a vacuum plug or something? You should be able to push a pipe cleaner or rod through the port into the bore.
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I will try that.the manifold side is where my dist is hooked up and engine runs fine I wonder if guage has a problem
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well I did some more checking turns out I don't have a 1406 I have a 1400. According to Edelbrock on the 1400 both sides are ported with the only manifold vacuum going to the PCV valve and the port out the back for the power brakes. Guess I didn't need a vacuum gauge
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Bummer. Well, I wouldn't tee it in to either of those. 1) I wouldn't mess with the PB line, and 2) don't hook it to the PCV line because it'll gunk up over time as dirty crankcase air cycles in and out of the advance can.
If you notice an off-idle balk, then I would hook the vacuum advance to a vacuum port on the intake manifold. You need a pipe fitting to hose nipple doodad for that, like one of these:
https://www.google.com/search?q=intake+manifold+vacuum+port+fittings&source=lnms&tbm=isch&sa=X&ei=Fz7CU4vUNsSsyASFpYH4Dw&ved=0CAYQ_AUoAQ&biw=1093&bih=858
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cool. Thanks for that.