I will be modifying my carbed 350 this summer and I will be swapping out my q-jet for something with better driveability & performance, but I want to keep ALL emmisions equipment on it and active. It will be mounted on a motor with about 400 ft-lbs of torque and 400 hp. I need to know what the q-jet has: manual/electrical choke and mechanical/vacumn secondaries? I have to tap the gas pedal before starting and it idles high until it warms up. I have a computer out of an 86 L69 car controlling it now. Basically, I would rather not have to let my car warm up so long and have that high-idle at start up for noise reasons after I get my new setup and general convienence. What can I do to help solve my problems? Obviously I don't know much about carbs, but I do want to keep it carbureted. Any suggestions?
Thanks, guys.
John

Any suggestions? Yeah, keep the q-jet and have it tuned correctly! A q-jet will work fine on a slightly modified 350. All those problems you mentioned sound like a carb that needs a tune up... nothing more. There is no real way to keep the emissions stuff functional without the q-jet. There are ways to pass the e-check though without it too... I do just fine with a visual even!

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

You have no choice but to keep the computer controlled QJet that came with your car if you want to stay emissions compliant. There is no emissions-legal high performance replacement for it.

Having to tap the gas before starting and the elevated idle speed when cold is absolutely normal and the carb is designed to work like that from the factory. On a dead-cold engine you should idle at about ~1200. If yours is revving too high, however, there is an adjustment for the cold idle speed- it's a screw on the pass. side of the carb, underneath the choke linkage. You can see it if you look underneath the choke linkage from the front of the vehicle.

But don't drop the idle speed much below 1000 when cold. Carb'ed engines don't idle well at low speeds when cold. It's not like fuel injection in that respect.

The Qjet you have can be upgraded for significantly better forformance even on a modified engine, however. There's a tech article on this website about it. Also, if you hang out and read some of the posts about the QJet here you're likely to pick up a lot of info, too.

Mine idles at about 2000 rpm dead cold and it takes forever to get to the point where it kicks down. I realized that it was supposed to idle high, i was just wondering if another carb design would make this a little bit less of an annoyance. Thanks for letting me know about the high-idle speed, I'll be looking into fixing that. I always thought that it was kind of dumb for it to idle that high because the oil hasn't circulated well yet. I was always thinking about how much wear that was putting on the internals of my engine. As for keeping the q-jet, Do you know how many cfm it can flow if I set it up right? Oh and one more question, will I need to make a custom chip for my computer with all the mods I'm doing? (heads, cam, intake, headers, high-flow cat & cat-back, maybe gears) Thanks,
John

John, check your vacuum secondary pull off linkage. make sure it pulls the choke plate slightly open on cold start up. Also check your electric choke for power or proper operation. My q jet used to idle forever from 1500 to 2000 rpms till I corrected those problems.

Yeah, definately check to see your choke plate is opening correctly. With the car off, it should snap shut when you move the throttle bracket. When you start the engine, it should open up about 2mm and continue to open all the way as it warms up.

A q-jet can flow about 750-800cfm. And chips are a serious waste of money! They do absolutely nothing on a q-jet.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

Well I just found the screw you're talking about, and adjusted it (first the wrong way but I figured it out ) Thanks a bunch man, it was so frickin loud before and I was worried about my neighbors getting even more pissed after I mod it. And now that I know it can flow that much, I guess I will keep it after all. I will just rebuild the sucker so its perfect. So these things have electric chokes and vacumn secondaries, right? I also checked the choke plate and it does exactly what you said it should. You guys are great!

Glad we could help out. Yeah, electric choke and SORT OF vacuum secondaries. The secondary throttle plates are direct-linked to the primaries (so they are TECHNICALLY mechanical secondaries) but with a flow-sensing secondary air valve on top of the secondary throttle bores. Effectively, it's a vacuum secondary carb.

Check out my post about getting more performance from the LG-4 carb in this forum. I just went through it a few weeks ago- it would all apply to your carb, too.

BTW- if you're from the Philly area we're probably not too far from eachother. If you get stuck and need some help sorting out the carb (or anything else on your ride) drop me an email.