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Q-Jet Vacuum Ports

fine69

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Dec 12, 2004
Messages
975
Location
Maryland / D.C.
Corvette
'69 Convertible Vette; '72 Z28 Camaro Rally Sport
Hi All,

I finally hooked up the Q-Jet system with the fuel line, filter with the return line. She started right up, but I do need to set the timing, etc.

There two different vaccum ports on the front of the carb, the one on the right (near the fuel inlet) situated high, and another situated lower that is on the left.

Which port connects to the vacuum line for the distributor?

Thanks.
 

Wayne robson

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Joined
Feb 24, 2007
Messages
169
Location
australia
Corvette
sold my last corvette.
try and help

hi fine 69, with rochester you dont disconnect at the carb you disconnect the the vacuum hose from the distributor and plug the hose there, then you know its correct not like on other carbs like some carter strom berb etc that only has one vavum hose, but also if you have not checked your dwell for a long time that should be done first, also try and get your idling speed correct before starting thats i mean specs for your model,thats where alot of tuneups are done wrong because there idle is to high and allow for approx 100 revs drop when vacuum hose is off and remember to loosen your distrbuter base a little before you start its alot easyer , regards wayne down under.
 

Bill75

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Joined
Jan 1, 2004
Messages
698
Location
Somers CT
Corvette
75 Coupe ZZ4, Brodix IK-180's, Headers,TK0-500
My carb different for some reason and may not help you but here it is anyway. My dist is hooked to the top right port.

CarbVacLines.jpg
 

Wayne robson

Well-known member
Joined
Feb 24, 2007
Messages
169
Location
australia
Corvette
sold my last corvette.
hi wayne here

My carb different for some reason and may not help you but here it is anyway. My dist is hooked to the top right port.

CarbVacLines.jpg
hi fine 69 all those hoses on your carb you leave where they are., regards wayne, i mean right over the back at your distributor base where it connects to your vacuum , thats where you disconnect and plug, i can see it on your top left photo where it connects
 

fine69

Well-known member
Joined
Dec 12, 2004
Messages
975
Location
Maryland / D.C.
Corvette
'69 Convertible Vette; '72 Z28 Camaro Rally Sport
hi fine 69, with rochester you dont disconnect at the carb you disconnect the the vacuum hose from the distributor and plug the hose there, then you know its correct not like on other carbs like some carter strom berb etc that only has one vavum hose, but also if you have not checked your dwell for a long time that should be done first, also try and get your idling speed correct before starting thats i mean specs for your model,thats where alot of tuneups are done wrong because there idle is to high and allow for approx 100 revs drop when vacuum hose is off and remember to loosen your distrbuter base a little before you start its alot easyer , regards wayne down under.

Thanks Wayne. Yeah, I completely understand the procedures on to tune up, check vacuum, dwell, timimg, etc. thanks to JohnZ's articles... that is with the Edelbrock --- but, I maaay need to get some help with the Q-Jet. But for now I was not sure which port to connect the vacuum advance hose.
 

fine69

Well-known member
Joined
Dec 12, 2004
Messages
975
Location
Maryland / D.C.
Corvette
'69 Convertible Vette; '72 Z28 Camaro Rally Sport
My carb different for some reason and may not help you but here it is anyway. My dist is hooked to the top right port.

Thanks Bill,

That's what I was looking for.

I believe the vacuum advance is supposed to be on full manifold vacuum, so I made the assumption that it was the lower port. That's what I see in your pic.

Thanks!

Ralph
 

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