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21
Quadrajet Carb Talk and Tips / Q-jet on 496bbc
« Last post by dualquad on October 12, 2025, 07:54:02 PM »
I am building a 496 bbc for my 69 chevelle. The motor should be approx. 600hp. I would like for it to appear to be a 396 350hp, so I plan on using a factory cast iron high rise intake with a Q-jet. My question is, what should I do for the fuel delivery system? Is anyone running a Q-jet on a 600hp street car? Looking for recommendations from those that have experience with a similar set up. Thank You.
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Quadrajet Carb Talk and Tips / Re: Specs for a 17058204
« Last post by Cadman-iac on October 11, 2025, 12:46:33 PM »
Rick,
float setting is 15/32" for both units.

 That's great, thank you very much Kenth. Have a great weekend.
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Quadrajet Carb Talk and Tips / Re: Specs for a 17058204
« Last post by Kenth on October 11, 2025, 05:39:28 AM »
Kenth,
 I forgot to ask about the float settings for these.  Would you mind posting those for me. 
 Thank you very much.   
 Rick

Rick,
float setting is 15/32" for both units.

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Dialing in your rebuilt Quadrajet carburetor / Re: Adjusting Secondary Air Flaps
« Last post by quadrajam on October 11, 2025, 04:15:12 AM »
If you need a spacer go with a 4 hole phenolic.

QJ
25
I'd go to .074" main jets and test again.  It's telling you that it wants a little more metering area since you have the power piston adjusted to full height and not quite getting the desired results.....
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Dialing in your rebuilt Quadrajet carburetor / Re: Adjusting Secondary Air Flaps
« Last post by Cliff Ruggles on October 11, 2025, 01:05:49 AM »
"I do have a 1/2” open spacer under the carb, and recently I read that you tested those and found they actually hurt performance on dual plane intakes. So I probably need to rethink that."

That's too much open area above the divider.  I've tested open spacers and open gaskets.  More thatn about 1/4" of open area between the carb and dual plane intake can and will cause transition issues going quickly to full throttle.  I'd get rid of the spacer or make a divider for it.....
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Quadrajet Carb Talk and Tips / Re: Specs for a 17058204
« Last post by Raoul Ross on October 10, 2025, 04:24:24 PM »
Here is the California 17058504 unit:

Where do you find that info?
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Quadrajet Carb Talk and Tips / Re: Specs for a 17058204
« Last post by Cadman-iac on October 10, 2025, 03:51:26 PM »
Here are the specs i have found on the 17058204:

(Airvalves are measured from back edge of open valve to the back side of chokeblade housing).

 Kenth,
 I forgot to ask about the float settings for these.  Would you mind posting those for me. 
 Thank you very much.   
 Rick
30
Quadrajet Carb Talk and Tips / Quadrajet vacuum ports
« Last post by Cadman-iac on October 10, 2025, 03:33:56 PM »
 Cliff,

 On each Quadrajet I've ever seen, the vacuum ports all have a letter designation, but nowhere have I found a chart or list of what each of these is typically used for.
 Of course some are obvious, such as the PCV, brake booster, choke pull-off, but some are not always easily identified.
 What I mean is, which one would typically be used for the EGR, or the emissions vapor canister, (and that could have 2, one for the control, and the other for the evacuation). And then there's the vacuum advance which can be either manifold vacuum or ported.

 Is there any such chart or list of port functions on the Quadrajet?

 I'm trying to figure out which port i can use for the emissions vapor canister. On my 88 Burb with the original TBI, it had a line coming from the canister to the TBI which was connected to a port that didn't apply vacuum until the throttle was opened slightly, and it didn't apply much. The port split internally and went to each side.

 When i did the swap to the Quadrajet, initially I used an older vapor canister that had multiple lines, one of which was a control, another was the suction.
  In the interest of simplicity, I went back to the original vapor canister which has just 2 ports,one from the gas tank, the other to the engine.

 I think that port "K" on the front of the base plate is the one that should work for this, but I'm not sure it applies enough vacuum for the canister to evacuate properly.
 I want to use the canister to keep the fumes down, and to avoid any fire dangers, (plus it keeps the wife from complaining about the smell).

 The other one I'd like to know is the vacuum advance. I've seen port "H" used for this, but I've also seen this port use either manifold vacuum or ported vacuum. My question concerning this is, does it just matter what the original application was for any given carburetor as to which vacuum this port applies, or are these all supposed to be the same from carb to carb?
 I know, a complicated question, but I figured if anyone would know, you would.
 Thanks in advance,  Rick

 The port designations I've seen are these:
A,B, T, K, H, G, F, D, V, N, L,  but I've never noticed a C.
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