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Old 04-12-2018, 08:15 AM   #1
paintinx
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dimensions of quadrajet JETS

Hej ... i am currently planing to check
the mixture of my quadrajet carburetor.

to change the mix I perhaps need other jets with a smaller dimension.

to buy the right jets here in germany
I need to know what size the primary jets are.

i asume it is a "non metric" meassure ...

so i am looking for the right measures of the primary jets...

thx in advance, stephan

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Chevrolet Suburban 1979, 2WD, 7,4 ltr

(GM CORPORATE 14-BOLT)

CARBURATOR: 17059520 / 1449 CCP

VIN: TCS269F528860
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Old 04-12-2018, 11:47 AM   #2
geezer#99
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Re: dimensions of quadrajet JETS

Look in this link. Your carb number isn’t listed But you should be able to find a truck or van close to how your truck is set up. The jet sizes will be close to what you have.

http://www.digitalcorvettes.com/foru...ad.php?t=88376

There’s likely some info there to determine how to measure jet sizes.

Look here to buy some jets to experiment with.

https://quadrajetparts.com/bulk-pack...ets-p-732.html
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Old 04-12-2018, 12:56 PM   #3
SilverMiner
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Re: dimensions of quadrajet JETS

paintinx - It sounds like you want to dive into the fascinating world of Qjet tuning and optimization. Your carb number is correct for a 78/79 truck and fortunately has the hot air choke which is easily converted to an electric version. The primary circuit of a Quadrajet is controlled by more than just the jet size. The primary metering rods and the power piston spring are a huge part of the equation, and merely changing jet sizes isn't always done like it is with Holley or Edelbrock.

I would strongly suggest that you visit Cliff Ruggle's site and buy his book. I've been messing with Qjets for years but didn't achieve real success until I followed his instructions and used his kits. Perhaps the best service he offers is a complete tune kit - give him your engine specs, and he'll sell you the correct jet, metering rod, idle tube and power piston spring for your application. He also runs an excellent forum on the site which provides excellent help and advice. I can state from personal experience that once a Qjet has been properly dialed in, it is difficult to distinguish from a comparable rig with aftermarket throttle-body fuel injection.
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Last edited by SilverMiner; 04-12-2018 at 05:22 PM.
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Old 04-13-2018, 06:51 AM   #4
paintinx
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Re: dimensions of quadrajet JETS

Thx Geezer and Silverminer.

I bought the book a few mounth ago, have read it and then ...
forgotten to use it ... very bad.

nice tipps! thumbs up!

Stef
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Old 04-18-2018, 02:32 PM   #5
Flathead Smith
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Re: dimensions of quadrajet JETS

There should be a number engraved on top of the jet. That number is the jet size in thousands of an inch. So for example, a #68 is 0.068" and a #72 is 0.072". I think most stock Quadrajet jets ran from #66 to #78, though I'm sure the aftermarket offered other sizes.

Figuring that ethanol has about half the BTU content of gasoline and that it is mixed at around a 10% blend here in the States, I guessed that increasing the jet size 5% would be about right. So I increase the jet size from #68 to #72 and it did help drivability of my truck, though fuel mileage dropped about 5%, which is what one would expect.
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Old 04-19-2018, 04:26 AM   #6
paintinx
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Re: dimensions of quadrajet JETS

hej flathead, u r right.
"Heizwert von Flüssigkeiten" - yesssss - so I decided to stay with my 0.072inch jets.

(and I am currently read/ing the suggested book from Cliff Ruggle ... - thx again!)

Stephan
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