Full vacuum on rochester carb - The 1947 - Present Chevrolet & GMC Truck Message Board Network

71-longbed · 10-10-2005, 06:31 AM

Where can i find the correct port on a Rochester q-jet 4MV ... to get full manifold vacuum ... want to double check myself

thanks

68C15 · 10-10-2005, 07:12 AM

front, top of passenger side. sometimes it has a metal "T" tube.
back of baseplate near the large port for the power brake booster connection.
if I can find a cable to connect my camera-phone to the PC I can take some pics to explain.

dwaite72lnghrn · 10-10-2005, 03:13 PM

On my old q-jet the lower driverside pipe, Thats where the vacuum advance was on the old setup. Buy a cheap vacuum gauge at idle hookmit up to the port and you should have about 20" of vacuum, rev it up and the vacuum should drop a little, If it is ported at idle you would have no vacuum till you reved it up then it would go up to 20" then start to drop off.

71-longbed · 10-10-2005, 03:38 PM

this what the front of the carb looks like right now

pass. side top ----> vacuum advance

lower driver side ----> evap canister

10-10-2005, 06:31 AM	#1
71-longbed Its Magically Delicious Join Date: Jan 2003 Location: oregon Posts: 2,398	Full vacuum on rochester carb Where can i find the correct port on a Rochester q-jet 4MV ... to get full manifold vacuum ... want to double check myself thanks __________________ 71 C10 LWB 350sbc -TH350 12 bolt 3.42 Posi Of all my favorite things to do, The utmost is to have a brew. My love grows for my foamy friend, with each thirst-quenching elbow bend. Beer so frosty, smooth, and cold it's paradise pure liquid gold. Yes beer means many things to me that's all for now cus I gotta pee.

10-10-2005, 07:12 AM	#2
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	front, top of passenger side. sometimes it has a metal "T" tube. back of baseplate near the large port for the power brake booster connection. if I can find a cable to connect my camera-phone to the PC I can take some pics to explain. __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

10-10-2005, 03:13 PM	#3
dwaite72lnghrn Registered User Join Date: Jun 2002 Location: central pa Posts: 1,525	On my old q-jet the lower driverside pipe, Thats where the vacuum advance was on the old setup. Buy a cheap vacuum gauge at idle hookmit up to the port and you should have about 20" of vacuum, rev it up and the vacuum should drop a little, If it is ported at idle you would have no vacuum till you reved it up then it would go up to 20" then start to drop off. __________________ 72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne

10-10-2005, 03:38 PM	#4
71-longbed Its Magically Delicious Join Date: Jan 2003 Location: oregon Posts: 2,398	this what the front of the carb looks like right now pass. side top ----> vacuum advance lower driver side ----> evap canister __________________ 71 C10 LWB 350sbc -TH350 12 bolt 3.42 Posi Of all my favorite things to do, The utmost is to have a brew. My love grows for my foamy friend, with each thirst-quenching elbow bend. Beer so frosty, smooth, and cold it's paradise pure liquid gold. Yes beer means many things to me that's all for now cus I gotta pee.

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