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05-24-2008, 07:23 PM
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#1 |
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Back in the sticks
Join Date: Jan 2001
Location: Fordland, MO
Posts: 3,188
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Where to read vacuum?
Finally got my vacuum guage working yesterday. They put the needle on backwards. GRRRR. Anyway, I hooked it to the other side of the carb, the one I'm not using for vacuum advance. Will that be ok? Not sure if its full vacuum or if it will be inaccurate.
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1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty |
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05-24-2008, 07:31 PM
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#2 |
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Truck and auto performance nut
Join Date: Feb 2007
Location: McKinney,Texas
Posts: 3,848
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Re: Where to read vacuum?
you should have it connected to the intake manifold.
for reading....the lower the vaccum reading, the more fuel your engine is burning.
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Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken |
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05-24-2008, 07:41 PM
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#3 |
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Back in the sticks
Join Date: Jan 2001
Location: Fordland, MO
Posts: 3,188
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Re: Where to read vacuum?
Hmmm, just looked thru my carb manual and it says the port I'm using for the vacuum advance is ported for emissions. The other is full vacuum. Am I running the right one? I'll get a vacuum fitting for the vacuum guage that comes off the manifold then.
__________________
1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty |
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05-24-2008, 08:45 PM
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#4 |
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just can't cover up my redneck
Join Date: May 2004
Location: Columbus OH
Posts: 11,414
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Re: Where to read vacuum?
You should have both connected to full vacuum. A simple "T" fitting will do what you need. You probably have to slow your idle down some when you move the vacuum advance to full vacuum. It will pull in the advance and cause it to speed up some.
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05-24-2008, 11:04 PM
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#5 |
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Registered User
Join Date: Dec 2006
Location: Idaho
Posts: 210
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Re: Where to read vacuum?
It's a can of worms. Some folks prefer ported vacuum, and some prefer manifold vacuum. I'm running manifold vac.
Hook the vac gauge up to the intake.
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72 C2500 LWB 402 Sierra Grande 05 Odyssey 08 Tundra |
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05-25-2008, 02:53 AM
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#6 |
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just can't cover up my redneck
Join Date: May 2004
Location: Columbus OH
Posts: 11,414
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Re: Where to read vacuum?
There is no good reason to run ported vacuum. It is "old technology" that was really just an experimental "band-aid". It was part of the first "emissions conformation" tuning in the late 70s and early 80s. The "late" timing at idle increases exhaust heat, which help burn hydrocarbons and helped the catalytic converter work better...but it does nothing for performance or drivability.
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05-28-2008, 11:11 AM
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#7 |
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Back in the sticks
Join Date: Jan 2001
Location: Fordland, MO
Posts: 3,188
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Re: Where to read vacuum?
Thanks guys. Didn't get a chance to swap over to full vacuum, had to fly back to Japan on Sunday. I'll mess with it at Xmas though.
__________________
1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty |
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05-28-2008, 01:15 PM
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#8 |
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Registered User
Join Date: Feb 2004
Location: Fort Leonard Wood Mo
Posts: 299
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Re: Where to read vacuum?
I always hear that it's good to read it at the base of the carb on full vacuum port!
__________________
 '69 Chevy C10 400sb-350 crank 400 destroker!!! 377 2.02 dart pro1 alum.heads msd, holley db hooker pro-comps-3in exh. 3 spd. saginaw-3.73posi Flat Bed...want Reg bed...trades? |
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