CarburetorsCarb discussion and questions. Upgrading a Third Gen carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
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So I'm going through my Qjet and I want to change my primary jets to a 75 rather than whatever came in it (carb is going on a built 355). I've got the carb apart, well the top of it anyway (the directions that came in the rebuild kit are horrendous), and can see the prmary metering rods (at least I think that's what they are based on the diagram) that I presume go down into the jets, but I've no idea how to get to the jets themselves. They are underneath the float but I can't get the float out and I don't have any kind of tool to squeeze down in there. Any suggestions? Thanks!
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__________________ 1984 Pontiac Trans AM
350 4-bolt main bored .040
Sportsman II Heads, Pro Magnum Roller Rockers, Lunati Voodoo Cam
Hooker Headers, Custom Catback with Hooker Aerochamber muffler
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Re: Changing pimary jets on Qjet --- need some help
I assume that you are working with a CCC q-jet? If so, you have to take the lean mixture screw off (tallest object in there after you take the top of the carb off use a really small crescent wrench or a small Double D wrench) then you can take the black plastic parts out, then the float (don't lose the small parts), then you should be able to get to the jets IIRC. I can't think of a reason you would want to change the primary jets in a CCC carb though. Whatever, its your carb. Hope it goes well. It's been a few months since I took my carb apart. you may need to take the mixture solenoid out as well to get to the jets. that's just one more screw. Its all pretty self explanatory once you get in there.
Re: Changing pimary jets on Qjet --- need some help
Quote:
Originally Posted by RazorN8
I assume that you are working with a CCC q-jet? If so, you have to take the lean mixture screw off (tallest object in there after you take the top of the carb off use a really small crescent wrench or a small Double D wrench) then you can take the black plastic parts out, then the float (don't lose the small parts), then you should be able to get to the jets IIRC. I can't think of a reason you would want to change the primary jets in a CCC carb though. Whatever, its your carb. Hope it goes well. It's been a few months since I took my carb apart. you may need to take the mixture solenoid out as well to get to the jets. that's just one more screw. Its all pretty self explanatory once you get in there.
Thanks man. I've been having an issue with the car just cranking and cranking and cranking. Got spark to all cylinders and it starts if I pour fuel down the carb, but wont' stay running unless I keep my foot on it. So I'm wondering if something is clogged. Also, since I upgrade to a 350, I'm replacing my stock jets, whatever size they are, with a set of 75 primaries. Figure it can't hurt.
Re: Changing pimary jets on Qjet --- need some help
Yeah, could be a clog. Could also be your choke not working, your float improperly set... When you turn the cam on the side of the carb, does it squirt fuel into the primary bores? Is the choke set when the engine is cold, after you press the accelerator to the floor? Could you have a vacuum leak? There are plenty of reasons that you wouldn't get enough gas that wouldn't rwuire a complete tear down of the carb. Is this an issue that has been sneaking up on you, or all of the sudden happened after an engine swap or something like that?
From what I have heard, there is only one size of primary jets for this carb. The mixture is adjusted by the the amount of time that the rods stay in the jets, which is controlled by the solenoid. Be sure that you are not buying jets for the non CC carb because I don't think that they will work.
Re: Changing pimary jets on Qjet --- need some help
Quote:
Originally Posted by RazorN8
Yeah, could be a clog. Could also be your choke not working, your float improperly set... When you turn the cam on the side of the carb, does it squirt fuel into the primary bores? Is the choke set when the engine is cold, after you press the accelerator to the floor? Could you have a vacuum leak? There are plenty of reasons that you wouldn't get enough gas that wouldn't rwuire a complete tear down of the carb. Is this an issue that has been sneaking up on you, or all of the sudden happened after an engine swap or something like that?
After the engine swap. Carb worked fine on the 305. never idled right on the 355. Broken valve springs and some other issues later, I got it running and had it dynoed. Then one day I start having issues where it won't stay running when cold, I have to keep the gas on it to keep it running until ti's warmed up, then it idles poorly. Then one day I'm coming home from work and it starts sputtering on an off ramp and dies. Had to have it towed home. I tried my original carb (25 years old) and it made it idle perfect, but the mixture was off. Ran for 3 days, then the same as the new carb where it won't stay running without my foot on it though once warmed up, I mean really warmed up, it idled fine. Now it won't even do that. Now it just cranks, cranks, cranks...nothing. really irritating.
Re: Changing pimary jets on Qjet --- need some help
Wierd. I was thinking choke pull-off, but since you had the same thing happen to two carbs I'm not sure. Maybe rust from the gas tank? There's not much modification that the CCC qjet will handle because of the computer control, but it is capable of handling most any street engine you throw at it when the carb is stock.
I would say tear down the carb that is not attached to the car currently and look for any obvious problems. Look into the fuel pump maybe? I definately sounds carb related since you swapped the carb and it fixed the problem temporarily. Maybe the gasket you used tore and is causing a big vacuum leak. Make sure you use the 1/4 inch thick quadrajet gasket and use it only once. I'm not sure where else your problem could be.
