Quadrajet Trouble
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Away from home this weekend but thinking about my possible vacuum leak and have a question.
Can you still have a vacuum leak bad enough to cause all my problems but still pull 20" on the gauge at idle?
All u need to assume is the size of the leak as compared to the throttle blades in the carb. U wont get zero vacuum until the the throttle butterflys are nearly full open. And you car is still running with them closed but breaths through the tiny idle air passages leaving u 20"Hg vac. I guessing but a leak the size of a pencil will allow idle and near full vac.
Well the more u R&R the intake the better u get at it.
With all the trouble u have had i would suggest to back to a unmodified stock like intake - performer, weiand action plus, GMPP etc and use a vlv cover PCV or even just a breather in the vlv cover and no PCV.
A wide band O2 is a oxygen sensor that can measure air to fuel ratio from like 11:1 all the way to like 16:1 and is used for fuel mixture tuning. Without a cat converter all u need is to stick the sensor in the tail pipe (closer to the exh manifold the better though) and measure how the carb is mixing the fuel. Very accurate O2 sensors are under $300 now. I would bother buying a narrow band O2 sensor as they are only good for idle and low speed cruise near stoiciometric 14.7 A/F.
Can you still have a vacuum leak bad enough to cause all my problems but still pull 20" on the gauge at idle?
All u need to assume is the size of the leak as compared to the throttle blades in the carb. U wont get zero vacuum until the the throttle butterflys are nearly full open. And you car is still running with them closed but breaths through the tiny idle air passages leaving u 20"Hg vac. I guessing but a leak the size of a pencil will allow idle and near full vac.
Well the more u R&R the intake the better u get at it.
With all the trouble u have had i would suggest to back to a unmodified stock like intake - performer, weiand action plus, GMPP etc and use a vlv cover PCV or even just a breather in the vlv cover and no PCV.A wide band O2 is a oxygen sensor that can measure air to fuel ratio from like 11:1 all the way to like 16:1 and is used for fuel mixture tuning. Without a cat converter all u need is to stick the sensor in the tail pipe (closer to the exh manifold the better though) and measure how the carb is mixing the fuel. Very accurate O2 sensors are under $300 now. I would bother buying a narrow band O2 sensor as they are only good for idle and low speed cruise near stoiciometric 14.7 A/F.
Thread Starter
Le Mans Master
Joined: Apr 2013
Posts: 5,000
Likes: 1,056
From: Arlington TX
2024 C1 of the Year Finalist - Unmodified
2023 Restomod of the Year Finalist
2023 C1 of the Year Finalist - Unmodified
Away from home this weekend but thinking about my possible vacuum leak and have a question.
Can you still have a vacuum leak bad enough to cause all my problems but still pull 20" on the gauge at idle?
All u need to assume is the size of the leak as compared to the throttle blades in the carb. U wont get zero vacuum until the the throttle butterflys are nearly full open. And you car is still running with them closed but breaths through the tiny idle air passages leaving u 20"Hg vac. I guessing but a leak the size of a pencil will allow idle and near full vac.
Well the more u R&R the intake the better u get at it. With all the trouble u have had i would suggest to back to a unmodified stock like intake - performer, weiand action plus, GMPP etc and use a vlv cover PCV or even just a breather in the vlv cover and no PCV.
A wide band O2 is a oxygen sensor that can measure air to fuel ratio from like 11:1 all the way to like 16:1 and is used for fuel mixture tuning. Without a cat converter all u need is to stick the sensor in the tail pipe (closer to the exh manifold the better though) and measure how the carb is mixing the fuel. Very accurate O2 sensors are under $300 now. I would bother buying a narrow band O2 sensor as they are only good for idle and low speed cruise near stoiciometric 14.7 A/F.
Can you still have a vacuum leak bad enough to cause all my problems but still pull 20" on the gauge at idle?
All u need to assume is the size of the leak as compared to the throttle blades in the carb. U wont get zero vacuum until the the throttle butterflys are nearly full open. And you car is still running with them closed but breaths through the tiny idle air passages leaving u 20"Hg vac. I guessing but a leak the size of a pencil will allow idle and near full vac.
Well the more u R&R the intake the better u get at it.
With all the trouble u have had i would suggest to back to a unmodified stock like intake - performer, weiand action plus, GMPP etc and use a vlv cover PCV or even just a breather in the vlv cover and no PCV.A wide band O2 is a oxygen sensor that can measure air to fuel ratio from like 11:1 all the way to like 16:1 and is used for fuel mixture tuning. Without a cat converter all u need is to stick the sensor in the tail pipe (closer to the exh manifold the better though) and measure how the carb is mixing the fuel. Very accurate O2 sensors are under $300 now. I would bother buying a narrow band O2 sensor as they are only good for idle and low speed cruise near stoiciometric 14.7 A/F.
I would think these state inspection stations would have O2 sensors so maybe I can have it tested there to see if I'm running rich or lean.
