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> OT-Quadrajet 4MV question, My darkside teener carb prob
HalfMoon
post Sep 13 2014, 06:11 PM
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Hi all,
While this is slightly off topic it IS at least in reference to a teener, specifically my v-8 converted teener.
It's a 350 sb and it uses a 1970 Qaudrajet 4MV carb. I know alot of folks don't like these but when they're dialed in right they give a good blend of economy and performance.

My question is twofold-
1. No doubt you're familiar with the secondaries "air flaps" that are visible on the top of the carb but down deep are the secondary "baffles". You can manually open them up all the way wide but on the car the linkage only open them a crack. I imagine further opening is a function of engine air flow and demand. Or am I totally wrong and they are in fact supposed to open wide via linkage?
2. Has anyone ever experienced constant vacum at the port feeding the secondary dash pot? It's the one that's connected to the secondary air flaps on top. It's supposed to stop it's vacum when you get out of the primaries and get into the secondaries thus allowing the air flaps (the ones on top that you can see) to open. For some reason mine has constant vacum and as a result I can't get my secondary air flaps to open (so I've had to disable that dashpot and cap the vacum port).
That dashpot is supposed to prevent the air flaps from "bouncing open" and I assume I'm gonna get a bog when I do quick shifts if I don't resolve this problem :-(

Your experience is appreciated.
David
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ClayPerrine
post Sep 13 2014, 09:31 PM
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The air flaps on the top of the secondaries move the metering rods up and down based on airflow. The butterflys on the bottom are controlled by the throttle linkage. there is no vacuum or mechanical connection to the air flaps on top.

Some of the quadrajets have a lockout tab that keeps the secondaries from opening until the choke is fully opened. This is supposed to keep you from romping on the gas when the car is cold.

The jets and metering rods are much harder to replace than the Holly or Edlebrock carbs out there. GM tuned the Q-Jet on a dyno for a particular engine size/cam combo. So a 350 truck carb won't work correctly in an 350 Vette of the same year.
The metering rods and jets are not easy to get either.

I would suggest an Edelbrock EFI conversion. If you insist on keeping it carbed, then change the Q-Jet out for an Edelbrock street carb.


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HalfMoon   OT-Quadrajet 4MV question   Sep 13 2014, 06:11 PM
ClayPerrine   The air flaps on the top of the secondaries move t...   Sep 13 2014, 09:31 PM
HalfMoon   The air flaps on the top of the secondaries move ...   Sep 13 2014, 10:04 PM
messix   when the throttle is all the way open the secondar...   Sep 14 2014, 12:13 AM
HalfMoon   when the throttle is all the way open the seconda...   Sep 14 2014, 09:09 AM
messix   when the throttle is all the way open the second...   Sep 14 2014, 12:55 PM
HalfMoon   [quote name='HalfMoon' post='2085929' date='Sep 1...   Sep 14 2014, 09:51 PM
messix   [quote name='messix' post='2085995' date='Sep 14 ...   Sep 14 2014, 10:00 PM
messix   this might help https://www.youtube.com/watch?v=Wf...   Sep 14 2014, 12:32 AM
HalfMoon   this might help https://www.youtube.com/watch?v=W...   Sep 14 2014, 09:10 AM
Olympic 1.7   This was MANY years ago but I had a Carter Thermo-...   Sep 14 2014, 10:04 AM
HalfMoon   This was MANY years ago but I had a Carter Thermo...   Sep 14 2014, 09:37 PM
Maltese Falcon   This was MANY years ago but I had a Carter Thermo...   Sep 16 2014, 09:22 AM
Mike Bellis   How have you verified this problem? Vacuum is not...   Sep 14 2014, 10:23 AM
HalfMoon   How have you verified this problem? Vacuum is no...   Sep 14 2014, 09:40 PM
messix   on second thought.... have you checked to see if ...   Sep 14 2014, 12:59 PM
HalfMoon   Here is the throttle linkage that controls the pri...   Sep 14 2014, 09:58 PM
HalfMoon   And here is the dashpot that does not release (whe...   Sep 14 2014, 10:01 PM
Maltese Falcon   You are using a spread bore QJ manifold, right? Th...   Sep 14 2014, 11:58 PM
HalfMoon   This was the problem. The spring that creates tens...   Sep 15 2014, 09:24 PM
HalfMoon   :Qarl:   Sep 16 2014, 09:54 AM
messix   now get those plugs epoxied up! :shades2:   Sep 16 2014, 04:51 PM
Dr Evil   I bet it is the spring that creates tension on the...   Sep 16 2014, 05:24 PM
HalfMoon   I bet it is the spring that creates tension on th...   Sep 16 2014, 06:37 PM


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