RPMS Posted October 30, 2003 Share Posted October 30, 2003 Hey, guys. Okay, the engine is in, and now I'm ironing out the bugs. It's a relatively strong performer on the primaries, but when I press the accelerator to open the secondaries, all it gives me is an odd fluttery whistling sound from the carb. It sounds like there's a something caught in the carb throat, or maybe like I'm getting dozens of tiny backfires thorugh the carb? After about two or three seconds the fluttery noise fades, and the car picks up its heels a bit. With this being my first Qjet, I don't know how to interpret what it's doing. What do y'all think? Quote Link to comment Share on other sites More sharing options...
Guest Perry Posted October 30, 2003 Share Posted October 30, 2003 does it do this throughout the rev range? or just when you tromp it from low revs? does it do this when you slowly open secondaries? did you recently rebuild/take apart the carb? I'm totally guessing here but maybe the air doors aren't opening smoothly, they control secondary mixture via a needle. if they stick closed or open slowly you could be running rich until they open. flap them back and forth with your finger, they should open easily and smoothly, no sticking. Perry Quote Link to comment Share on other sites More sharing options...
Guest greimann Posted October 31, 2003 Share Posted October 31, 2003 They don't call them Quadrabogs for nothing. . Consider a Holley for easier tuning. Quote Link to comment Share on other sites More sharing options...
Guest low-budget Posted October 31, 2003 Share Posted October 31, 2003 Oh no! Not the dreaded quadrajet myths again . For all your quadrajet worries (I love q-jets myself) go here, check out the carb section, and you'll find gobs of awesomely helpful tips for tuning your q-jet. I couldn't tell ya exactly what is going on in your case, as I've not experienced those symptoms (mine just get up and gallop hehe), but I'm sure with a bit of tinkering you'll have it running like a scalded dog in no time . Hope this helps! Quote Link to comment Share on other sites More sharing options...
denny411 Posted October 31, 2003 Share Posted October 31, 2003 Some momentary lag or hesitation is normal from a Quadrajet. It`s just the nature of the vacume secondaries. If your cam has too much duration or valve overlap it could intensify this condition. At wide open throttle, manifold vacume drops to zero. As engine rpm`s increase, vacume rises and pulls the secondaries open. Have you tried driving the car yet, or are you just free reving it? They usually work better when driving than they do free reving. With a load on the engine, it is much easier for manifold vacume to keep up with engine rpm. Quote Link to comment Share on other sites More sharing options...
RPMS Posted November 3, 2003 Author Share Posted November 3, 2003 Hey, guys. Thanks for the replies! I chose the Qjet not because it was simple to set up, but because it has a reputation for both excellent driveability when you set it up right, and for staying in calibration once adjusted. No offense, but the word I hear is that if you're not smart enough to adjust your Qjet you can just slap on a Holley instead. You'll be running again, but it won't be as smooth or as streetable, and you'll have to tinker with it to keep it running right. Kinda like the Webber conversion from a SU carb. Now, this isn't gospel, it's just what I've heard. I've got a Holley DP in the garage waiting to be rebuilt. If someone can show me with dyno runs that the Holley makes more HP over more RPM's, I'll rebuild it and put it on instead. As a side note, I didn't have any beer to drink with my pizza, so I made myself a rum and coke instead. Man, that stuff is stronger than I remember. Please excuse any misspellings from here on in! Perry, it doesn't happen unless the accelerator is floored, and then it seems to happen at any RPM. I can punch it at either 10mph or 60 and it will do the same thing. What I have NOT tried is keeping it in second gear up to 3000 RPM then flooring it. I'll try that tomorrow morning and I'll let you know what happens. Maybe it will behave if the RPM's are up. Man - is it hot in here, or is it just me? Denny, I don't think it's quite the same problem as the secondaries taking a second to open. I'm not mashing the throttle to the floor, I'm gradually opening it over a 1 1/2 to 2 second period. The accelerator pump SHOULD compensate for the lack of vacuum (and I'm sure it's pumping gas out the orifice - I can hear it squirting in there when the engine is off), shouldn't it? And shouldn't the vacuum remain fairly high, since the air horn plates don't begin to open until airflow demands them to? I don't know - like I said, I'm ignorant of these babies. I think I'm going to lay down for a while. If you have any thoughts, please, share them! And if I start to dance around with a lampshade on my head, please shoot me. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted November 3, 2003 Share Posted November 3, 2003 I hope I didn't miss what you wrote. Anyway what about the accelarator pump diaphram? May be it's sucking air. I don't under estimate Q-jet. I got a friend with a 455 poncho putting down 400WHP with a Q-jet. Quote Link to comment Share on other sites More sharing options...
RPMS Posted November 3, 2003 Author Share Posted November 3, 2003 Heya, Yo. The Qjet was just rebuilt so the accel pump is new, but I guess that really doesn't answer your question, does it? I guess the walls of the resevoir could be corroded and not holding pressure, or something. How can I tell that the pump is delivering the full shot? Quote Link to comment Share on other sites More sharing options...
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