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By mac - 11 Years Ago
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i've been searching on here and google endlessly but i can't seem to find this info so:
i'm trying to do a vacuum test on my 292 with the stock autolite 2100 carb. so, not seeing any other vaccum lines i t'd into the distributor advance off the carb and got a steady 4 pounds vacuum. not good. did some research and from what i've seen that is ported vacuum and not really where i want to pull vacuum for a reading. my question is if i'm not supposed to use that, where can i get manifold vacuum? it has no vacuum powered accesories and i don't see any plugs or anything in the manifold or carb.
edit: i do see a threaded plug in the back of the manifold horizontal to the engine...
it's on a 64 f100, by the way. thanks in advance
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By speedpro56 - 11 Years Ago
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Go into the plug at the back of the intake manifold and that should do it.
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By Talkwrench - 11 Years Ago
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As above, put a fitting in there and run a vacuum gauge it will be your best friend.
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By mac - 11 Years Ago
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done and done guys, thanks! so my engine is running about 18-19 pounds, and the needle is fluttering. when i look at all the samples on google images of vacuum gauge readings with explanations as to what they indicate, i don't see something like that. i see where if it jumps between 14-19 quickly then worn valves, but it just flutters over 18-19, drops to 10ish when revved. what do you think? it idles a little rough and has a little hitch in it's get up when taking off from a stop. rebuilt the carb recently so i don't suspect the accelerator pump or power valve.
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By Hoosier Hurricane - 11 Years Ago
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Y Blocks have solid lifters, but in the latter parts of their lives, valve adjustments just don't seem to happen like they did when the engines were newer. Try adjusting the valves to .019 clearance and see if that doesn't help.
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By Talkwrench - 11 Years Ago
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That could be a very minor vacuum leak too. when it goes over 1200rpm does it level out?
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By Park Olson - 11 Years Ago
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In regard to VAC. readings, what is acceptable when under heavy sustained load? My 600 with a 292 pulls well at 2600, VAC. goes down to around 6". 19-20 at idle, I've set timing by VAC, unsure of pulley markings. It has a flat top 2 barrel.
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By vntgtrk - 11 Years Ago
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Park, that sounds like normal readings. If your vac doesn't go down when you rev it up, somtin' ain't right
OP, I second the possible vacuum leak motion. In the smog repair bidness we called it a lean miss. Time to get out the spray bottle filled with water (some peeps use WD40). If you don't get a change in idle/vacuum when you spray all the usual suspects, go for the throttle shaft, both sides. What I've been reading as of late indicates these 2100's are prone to wear in that area which can cause a vacuum leak.
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