Q-Jet Help

[vtblazer]

Just rebuilt the Q-jet on my 70 swb with a 350...still stumbles when you step on it (lightly) from cruise throttle position...?
I've tried several pump rod adjustments with no big change.
To top it off the upper gasket is wet I've checked the float level and it's fine. I even dropped it some.
I've got it so it drives "OK" but it seems like it could be allot better.
Step up, all you Q-Jet junkies...what are your thoughts/suggestions?

[68C15]

sounds like the airhorn ( top portion) is warped. common with these. there was a post on how to fix this not long ago. I am not computer literate enough to be able to link it in this reply.

[neonlarry]

From an article by Lars Grimsrud:
How can you tell if an off-idle stumble is caused by a lean or a rich condition?
A carb running rich, as well as a carb running lean, can cause an off-idle stumble or hesitation upon acceleration. To narrow it down, tap the roll pin out of the accelerator pump lever by using a small pin punch or a small finish nail. I actually use a small, broken drill bit that?s just the right size. Using a hammer, gently tap the roll pin in towards the choke air horn wall. Don?t jam the pin right up against the wall: Leave just a little bit of a gap so you can get a screwdriver blade in between the wall and the pin to pry it back again. With the pin tapped out, remove the accelerator pump lever. I like to do this with the engine running so I won?t have any trouble starting the engine without the accelerator pump. Now, rev the engine a little with the throttle. Notice if the engine seems quicker and more responsive, or if the hesitation & stumble is worse. If the engine actually feels more responsive with the accelerator pump disconnected, you have a rich condition. If the hesitation is worse than before, you have a lean condition. If there is no change whatsoever, you have a non-functional accelerator pump.

To verify a suspected lean condition after this test, simply hold your cupped hand lightly over the choke air horn area with the engine running at idle, restricting the air flow. If the idle speed and idle quality momentarily increases, you have a verified lean condition. You need to select a jet/rod combination that will give you a little more Cruise Metering Area. Make these changes in less than 10% increments using the Figures provided in this paper.

You can also check your air horn with a straight edge and back light it to see if its warped. If it is you can either file it flat or bend (very carefully or it will crack) it back.

[orangeuavol]

Ask Jhow66, he can tune one in the dark with one hand tied behind his back, ears plugged........He knows them inside and out.

[Robert1970C20rstbukt]

That's the same problem I'm having with mine. I tore it down like 12 times trying to figure out WTF was wrong with it, guess I'll try that tomorrow. When the engine's running, it floods really bad and if you get a flashlight and look into the carb, you can see gas streaming into the intake, so something ain't right.

[shuttermutt]

I know this is a really s&%tty reply that's prone to start a flame war and get people mad, but I've just gotta say that ditching the Q-Jet and putting on the Edelbrock was probably the single best upgrade I've made to any of my vehicles EVER. I know... I know... Q-Jets have a lot of things going for them, but they just aren't what I consider a part that likes to be tinkered with. The Edelbrock, on the other hand, is dead-stone simple and more tolerant of getting jacked with by someone that only thinks they know what they're doing.

[68C15]

you hit the nail on the head ther Shuttermutt. honestly if you are not a "Guru" with carbs go with the Edelbrok. I only have 2 problems with a Qjet. finding a good one that isnt messed up & the float bowl volume. second one only applies to constant high RPMs. otherwise they are a well designed & highly functional unit for stock to slightly modified engines

[vtblazer]

Threw in the towel after fighting for hours...
Even tried a 2nd q-Jet that did the same thing but worse
I started wondering if it could be ignition...so I took the Edlebrock off the blazer and it now runs sweet! Now I need to decide...do I put the Edelbrock back on the blazer or just get something new (better) for the blazer???
Any suggestions?
Thanks for all the input on the Q-Jet anyway though...

[LUV2XCLR8]

As 4 The Blazer, It Is Up To You On How Much Fiddln U Want To Do
With It, None = Edelbrock, A Lil = Barry Grant Street Series, Alot
Of Tunability = Holley, And I'm Sure There Are Others Out There

[ChevLoRay]

SHUTTERMUTT!!! Where HAVE you been? Last I knew, you were in Maine, man. Now, I see you're still livin' close to Canada....and that means snow.

Anyway, I went to the Edelbrock Q-Jet, from an Edelbrock 1405. I could have rebuilt it, but I gotta deal on the new Q-Jet, courtesy of the "Zone"....$289.

I was working at the Sears Auto Center in Little Rock, back in '76. Had a customer bring in an Olds Toronado. It had been in a week before for a tune up. But, it had a cylinder balance problem. Since it was a "come back" it fell to me. I checked everything on it, and the shop chief said it had to be in the carburetor....a Q-Jet. I tore it apart, cooked it, and reassembled it. It still had a miss. I tore it down again, just to check the bowl, top and throttle plate for warpage. No problems. Put it back together. Got a can of starting fluid, and found the intake was warped......the guy had let it overheat, but left the bit of info out of the writeup. I didn't want to mess with it, and I put him onto one the other mechanics who worked at home, on the side. So, the guy was told $20, and beer. The owner shows up, brings the beer, pays him for the work and they smoked a few joints at the same time, provided by the car's owner. I'm sure that in the long run, he spent more that it would have cost a Sears, but I'm glad he took it to someone else. I think it really was on the verge of needing some head work.

Anyway, this is something to be wary of, when you think you have a carburetor problem.....if it has ever overheated.

[shuttermutt]

Originally Posted by ChevLoRay

SHUTTERMUTT!!! Where HAVE you been? Last I knew, you were in Maine, man. Now, I see you're still livin' close to Canada....and that means snow.

Yep, I made the move from Maine to Minnesota in January. Drove the old '68 the entire 1,700 miles and then kept on driving it even when it hit -35 below zero. Hell, it ran while my wife's 2001 F-150 wouldn't start!

The plus side is that the new job pays a little better and I've got an honest-to-goodness garage to stuff my tools and tinker with the truck. The downside is that these last few months have been hectic as all hell. I think things are settling down a bit. I'm not gonna let 'em steal any of my summer when they're as short as they are up here!