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HalfMoon |
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Senior Member ![]() ![]() ![]() Group: Members Posts: 828 Joined: 13-November 12 From: Shenandoah Junction, WV Member No.: 15,144 Region Association: MidAtlantic Region ![]() |
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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Mike Bellis |
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Resident Electrician ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 8,347 Joined: 22-June 09 From: Midlothian TX Member No.: 10,496 Region Association: None ![]() ![]() ![]() |
How have you verified this problem?
Vacuum is not the only control on the secondaries. Air velocity through the carb opens them as well. Vacuum closes them, air velocity opens them. This cannot be checked in the driveway. It can only be checked on the road or rolling dyno. The system needs load and speed, otherwise they will stay shut. The Quadrajet was designed for multiple displacement engines. If you don't have the pumping volume (air flow) it will not open all the way. This is the design. So in some cases (small block engines) it will never open all the way. If it does open all the way on a small engine, the performance will suffer. |
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